Biological Journal o f l h e Linnean Sociey (1985), 24: 233-283. With 18 figures
The natural history of Beauchihe
Island
R. I. LEWIS SMITH AND P. A. PRINCE
Brilish Antarclic Survey, Natural Environment Research Council,
Madingley Road, Cambridge, CB3 OE T
Alcepled f o r publication 30 April 1984
Beauchene Island is the most isolated of the Falkland Islands archipelago and until the authors’
visit there in 1980 little was known or published about the island and its biota apart from its
avifauna. The first collections and identifications of various plant and invertebrate groups were
made and a brief account of their ecology and interrelationships is given; many of the arthropods
are first records for the Falkland Islands and some are new to science. More detailed information is
presented for tussock grass (or tussac), Poajlabellala, which reaches a height of 3.5 m and covers
two-thirds of the island with a unique monospecific grassland. The underlying deep peat, in places
reaching 13 m depth, was investigated and radiocarbon dates obtained at various levels through the
profile, indicating that the grassland has existed virtually unchanged for 12 500 years. The status of
the avifauna was assessed. The black browed albatross and rockhopper penguin colonies were
counted reasonably accurately and calculated to contain up to 170000 and 300000 pairs,
respectively. A population of about 250 striated caracaras was counted, together with 67 nests,
possibly the largest concentration of these rare raptors anywhere. The recently discovered
population of fairy prions was estimated at several thousand birds. Se’a lions were not abundant and
fur seals, once said to occur in large numbers on the island, were abseht. The biological simplicity of
the exceptionally uniform tussac ecosystem offers ideal conditions for testing ecological hypotheses,
especially those related to trophodynamics and predator-prey interrelationships, and its potential
for research is emphasized. The importance of applying strict conservation measures to protect this
unique island is stressed in view of the possible future economic development of the Falkland
Islands.
KEY WORDS:--Falkland Islands - flora - Poajlabellata - peat deposits - seals, birds, invertebrates
~
tussac ecosystem - conservation.
CONTENTS
Introduction . . . .
General features . . .
Geology and geomorphology
Climate and hydrology
.
Vegetation
. . . .
Microbiology . . . .
lussock grass . . . .
Peat deposits . . . .
Stranded trees.
. . .
Seals . . . . . .
Birds . . . . . .
Invertebrates . . . .
Discussion.
. . . .
Acknowledgements
. .
Kekrences.
. . . .
+
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0 1985 The Linnean Society of London
234
R. I. L. SMITH AND P. A. PRINCE
INTRODUCTION
Beauchtne Island is the southernmost and most isolated of the Falkland Islands,
situated at latitude 52”54’S, longitude 59’09’W in the South Atlantic Ocean. It lies
about 80 km south of Porpoise Point on the mainland of East Falkland Island and
5 1 km south of Sea Lion Islands, the nearest land to Beauchtne Island. It was visited
sporadically between the early 1800s and early 1900s by sealers but these landings
have been very poorly documented. The discovery, charting and early history of the
island have been described by Smith ( 1984).
Little was known about the island’s biota and environment until i t was visited
by a naval party from H.M.S. Protector in December 1962. There followed a
series of six visits by the Falkland Islands naturalist I. J. Strange between 1963
and 1972. Strange (1965a, 1976a) has provided the only accounts of the island
and of some aspects of its natural history, especially the avifauna. Of particular
interest were his estimates of the numbers of breeding rockhopper penguins and
black browed albatrosses, which constitute one of the largest mixed populations
of birds in the world and one of the largest albatross colonies. He also reported
the occurrence of a breeding population of fairy prions previously unknown
from this sector of the Southern Ocean, a substantial population of striated
caracaras, which are now extremely rare, and an exceptional depth of peat
beneath the island’s dominant vegetation of tussock grass. H e confirmed that
there were no longer any fur seals, which were present in large numbers during
the eighteenth and nineteenth centuries and were said still to occur on
Beauchtne Island in substantial numbers. He also found the sea lion population
to be very much smaller than had previously been suspected.
In March 1977 one of the authors (R.I.L.S.) made a brief visit to the island
to assess the possibility of making a more comprehensive biological and
ecological survey. This was eventually achieved when the authors stayed on the
island from 9 to 24 December 1980 with the following principal aims:
(1) to make an accurate census of the breeding avifauna, especially black
browed albatross, rockhopper penguin and striated caracara populations
(there had been much controversy over Strange’s (1965a) estimates);
(2) to determine the prey of these species for comparison with feeding studies
carried out at Bird Island, South Georgia;
(3) to obtain biometric data on the fairy prion population;
(4)to assess the status of sea lions on the island;
(5) to make a survey of the flora and vegetation and a study of the tussock
grass for comparison with the species on South Georgia where it has been
investigated in some detail;
(6) to examine the deep peat accumulated beneath the tussock grass and
obtain samples for radiocarbon dating;
(7) to make a preliminary survey of the invertebrate fauna;
(8) to examine the interactions between the environment, fauna and tussock
grass ecosystem.
GENERAL FEATURES
Beauchtne Island (Fig. 1 ) is a little over 3 km long and 1 km wide at its
widest point and aligned in a north-south direction. It has a total area of
THE NATURAL HISTORY OF BEAUCHENE ISLAND
235
t<FJTussock grassland
0Mixed black browed
albatross and rockhopper
penguin colonies
0
500
1
1
1
.
I
I
"The
Citadel"
rn
59009'W
Figure 1 . Map of Beauchine Island showing distribution of tussock grassland and mixed black
browed albatross and rockhopper penguin colonies.
approximately 187 ha, of which about 113 ha are covered by dense tussock
grassland and 35 ha support mixed albatross and penguin colonies. As noted by
Strange ( 1965a) the island comprises three topographical areas:
(a) The northern two-thirds is relatively broad and consists of a plateau, rising
30-60 m in sheer cliffs from the sea on the east side, and tilting gently to the
west where the coastline ranges from cliffs up to 25 m high to boulder beaches
and areas of shelving rock platforms in the south-west of the area (Fig. 2). Most
of this section is capped with tussock grass or tussac overlying deep peat, but the
236
R . I. L. SMITH AND P. A. PRINCE
Figure 2. General view of west side of Beauchene Island looking north. Gentoo penguin colony in
foreground and the main mixed black browed albatross and rockhopper penguin colony in
background. Tussac grassland overlies deep peat at top right, reaching 13 m depth at top centre.
gently sloping western coastal area consists of angular boulders and mud of peat
and guano. The highest point is 82 m above sea level towards the mid-east of the
region. There is a wide shallow depression near the north-east corner of the
island.
(b) The central waist of the island is mainly low-lying with a tussac-covered
ridge of about 35 m altitude running along its length. The eastern coastline is
mainly of shelving rock platforms with several stacks, while the western coastline
consists mainly of an extensive broad beach of rounded boulders up to a metre
across. In the middle of the island, where the northern and central areas meet,
there is a large hole about 100 m across and 50 m deep, penetrating to sea level
and entered by the sea through a large cave running about 150 m from the cliffs
on the east coast.
(c) The southern area is also narrow but the southern extremity is high,
unvegetated and consisting of areas of level gently sloping rock platforms,
massive flat rock slabs, often unstable, and areas of smaller slabs and boulders,
sometimes loose and unstable but locally embedded in a muddy ‘soil’ (Fig. 3).
At the southern end of the island these boulders and slabs lie on a high rock
platform about 75 m above sea level and separated from the lower area to the
north by a major fault. This entire southern area is surrounded by impressive
vertical cliffs indented with caves and narrow inlets.
GEOLOGY AND GEOMORPHOLOGY
The island is geologically uniform, of the same formation of coarse whitish
quartzite that occurs throughout much of the Falkland Islands (Greenway,
THE NATURAL HISTORY OF BEAUCHENE ISLAND
237
Figure 3. General view of Beauchene Island looking south towards 'The Citadel'
1972). The rock platforms dip very gently at angles of 1-5", mainly in a northeast but elsewhere southwest, direction. No dykes or sills were noted but
numerous exotic rounded pebbles up to 10 cm across of dark grey sandstone,
siltstone and mudstone, some of which possibly contained impure limestone,
were found in depressions on the northern part of the southern area at about
20 m altitude and 150 m inland from the east coast. These sedimentary rocks do
not appear to be of local origin and were presumably deposited there by
exceptionally rough seas during storms from the east or southeast, although it is
difficult to imagine the provenance of these stones considering the great depth of
water around the shores of the island.
The boulder beach on the windward west coast of the waist area and also at
the northwest corner of the island had numerous spherical vesicular grey
boulders of pumice up to 35 cm in diameter. These may have originated from
volcanic activity on the sea bed in the South Shetland Islands, the nearest
source of volcanism, 1000 km to the southwest, although it is not inconceivable
that they derived from the South Sandwich Islands, 2000 km to the southeast,
and reached Beauchine Island after circumnavigating the world (e.g. Coombs
& Landis, 1966).
In the southeast corner of the island just north of the major fault is a short
ridge of coarse compacted sandy material about 5 m high, resting on a rock
platform and containing quartzite stones and occasional outcrops. Below this
ridge, erosion has left several large boulders perched on narrow columns of this
material 1-2 m high (Fig. 4).In places, notably on the crest of the ridge, there
are contorted bands, up to 3 cm wide, of a hard and heavy concretion
resembling an iron pan. Nearby and elsewhere beneath tussac there is a fine
clay deposit, up to 1.5 m deep, in which there are lenses of a white soft mineral
composed mainly of potassium aluminium phosphate. Although often small and
R. I. L. S M I T H AND P. A. PRINCE
238
Figure 4. Perched quartzite boulder on 2 m high column of sandy soil and decomposed rock. Southeast Beauchhe Island.
isolated, in places it occurs as discontinuous bands about 5 cm thick and 30 to
50 cm long. The chemical composition of these minerals is given in Table 1.
CLIMATE AND HYDROLOGY
No climatic data are available for Beauchhe Island but it probably
experiences weather comparable with the southern mainland of the Falkland
Islands (ix. mean temperature for the warmest month (February) 9.2"C, mean
Table 1. Chemical analysis (as percentage dry weight) of minerals in
Beauchhe Island soils
Sample
1
SiO,
AI,O,
FeP,
MgO
CaO
Na,O
KZO
TiO,
MnO
PZO,
S
c1
52
I1
22
0.7
0.2
1
2
0.5
0.2
4
0.3
1
Sample
Sample
2
3
75
19
2
1
0.2
1
2.5
0.6
0.2
1
0. I
0.5
6
23
I
0.5
<O.l
0.5
7
<0.1
0.2
47
0.2
1
Sample I: Dark brown concretion occurring as irregular narrow bands in sandy soil.
Sample 2: Light brown matrix in which sample 1 is embedded.
Sample 3: White concretion occurring as lenses and discontinuous bands in sandy clay.
All samples had a relatively high H , O but low CO, content. The chemical composition was determined by
X-ray fractionation.
THE NATURAL HISTORY OF BEAUCHENE ISLAND
239
for the coldest month (July) 2.1°C, annual mean 5.6”C; annual precipitation
about 600mm with August to November being the driest months and
December and January the wettest; mean annual wind speed 8.2 m s - I , as
recorded at Port Stanley between 1951 and 1981). Precipitation at North Arm
in the south of East Falkland Island is only 400 mm. The low topography of
Beauchtne Island, the extreme dryness of the tussac litter and peat deposits, and
absence of any streams may indicate low rainfall. The prevailing wind is from
the southwest and the island is undoubtedly exposed to frequent strong winds
and the coast must often be battered by heavy seas. Landings are notoriously
difficult by boat. During the authors’ stay on the island a heavy swell persisted
for three days although the wind was not strong. O n one of these days waves
breaking against the southeast cliffs reached about 30 m and the entire island
was deluged with heavy spray. An early reference to such conditions is given in
the Nautical Magazine (Anon, 1832): “The Eden was overtaken by a furious
gale, between Beauchene and Porpoise Point, with thick snow and hail storms,
when, not being able to weather Beauchene, nor to see around, Captain Owen
was obliged to seek a port. Two days afterwards, the Durance, a French frigate
store-ship was placed in similar circumstances, and just weathered Beauchene”.
Fresh water exists only in the form of a small stagnant pond, c. 35 m by 15 m,
towards the southwest end of the tussac grassland. Numerous brackish rock
pools occur near the shore line. A ‘stream’ of barely moving water issues from a
grotto in the vertical peat face adjacent to the main bird colony on the west side
of the island. The grotto could serve as a source of drinking water were it not
occupied by bathing penguins; this ‘stream’ and occasional other more
temporary water courses, flows through the seabird colony.
VEGETATION
The flora of Beauchtne Island is remarkable for its paucity of species
(Table 2). All collections made during this survey are deposited in the
herbarium of the British Antarctic Survey (AAS). Although Morrell (1832)
described the island as barren, about two-thirds of its area is covered by tussac
or tussock grass (Poa Jlabellata), which is also clearly shown in Fanning’s (1834)
illustration of the northeast corner of the island. While Strange (1965a, 1976a)
did not record any other vascular plant species, he noted (Strange, 1965a) that
“the landing party in 1962 reported that in a few places, where the tussock was
lower and more open and the ground damper, there were other plants in
association and one species of umbellifer, one composite, and a ‘small blue
flower’ were mentioned. No specimens were collected.” The only other
terrestrial plant noted by Strange was patches of the lichen Verrucaria in the
supralittoral; in fact the genus referred to was probably the prominent orange
lichen Caloplaca.
Angiosperms other than tussock grass
One of the authors (R.I.L.S.) made a thorough search for plants but
discovered only three vascular species besides P. Jlabellata. All were very rare and
growing on moist tussac litter beneath the grass canopy where it was less dense.
None was seen in rock crevices or on ledges although possible sites, which were
13
240
R. I. L. SMITH AND P. A. PRINCE
Table 2. List of plants recorded on BeauchZne Island
ANGIOSPERMAE
Gramineae: Poa Jabellala (Lam.) Rasp.
Cruciferae: Cardamine glacialis (Forst. f.) DC.
Umbelliferae: Apium australe Thouars
Callitrichaceae: Callitriche anlarctica Engelm ex Hegel.
MUSCI
Eryurn pseudofriquetrurn (Hedw.) Schwaegr.
Calyptrochaete apiculata (Hook. f. et Wils.) Vitt.
Campylopus introJexus (Hedw.) Brid.
Campylopus cf. modestus Card.
HEPA’TI CAE
Clasmatocolea vermicularis Lehm. & Grolle
Lophocolea divaricata Herz.
Lophocolea lenta (Hook. f. et Tayl.) Tayl.
Lophocolea leptantha (Hook. f. et Tayl.) Tayl.
Telaranea pseudozoopsis (Herz.) Fulf.
LICHENES
Arthropyrenia sp.
Buellia conzops (Wahlenb. ex Ach.) ‘lh. Fr.
Ruellia punctata (Hoffm.) Massal.
Caloplaca cinochrooides (Vain.) Zahlbr.
Caloplaca sublobulata (Nyl.) Zahlhr.
Lecanora cf. lavae Darbish.
Lecanora subfica agg.
Mastodia tesselata (Hook. f. et Harv.) Hook. f. et Harv.
Verrucaria ceulhocarpa Wahlenb.
Verrucaria durietzii M. Lamb
Verrucaria maura Wahlenb.
Verrucaria mucosa Wahlenb.
FUNGI
Cladosporiurn cladosporioides ss. lato
Coprinus hemerobius Fr.
Panaeolus subbalteatus (Berk. & Br.) Sacc.
Puccinia striiformis
ALGAE
Ankistrodesmus sp.
Hazenia sp.
Oedocladium sp.
Prasiola crispa (Menegh.) Lightf.
not examined due to their inaccessibility, may occur along the rock outcrops
and terraces above the northeastern cliffs.
The most widespread of the three forbs was Cardamine glacialis (Fig. 5a), small
groups of which were found in several localities but mainly at the northern end
of the island. A large population of mature plants and seedlings at the tussac
margin in the northeast of the island covered an area of about 5 x 3 m and was
flowering profusely, with flower stems up to 35-40 cm tall (Moore, 1968, states
the maximum height of this species in the Falkland Islands as being 35 cm).
Other plants were scattered over the adjacent area of about 25 x 25 m. This
Cardamine site was also the main locality for Callitriche antarctica (Fig. 5b), which
formed several low compact circular mats associated with C. glacialis. It also
occurred in a few scattered localities along the northwest tussac margin,
forming mats up to 50 cm across. Plants were considerably taller (up to
10-12 cm) than have been recorded in similar habitats on South Georgia or the
THE NATURAL HISTORY OF BEAUCHENE ISLAND
Figurc 5. 'l'hr only thrcc forbs recorded from BeauchPne Island: (A) Cardarnine glacialis (knife handle
is 10 cm long), (B) Callitriche a n t a r c h and (C) Apiurn australe.
24 I
242
R. I. L. SMITH AND P. A. PRINCE
Falkland Islands (Greene, 1964; Moore, 1968). Callitriche antarctica produces
large numbers of apetalous flowers.
The third forb, Apium australe (Fig. 5c), was recorded at two sites, both on the
very steep wall of ‘The Hole’. The main site was about half way down the
tussac-clad south wall where the wild celery and many seedlings were scattered
over an area of about 8 x 2 m. It was flowering profusely and flowering stems
reached 95 cm, almost twice the height recorded in the Falkland Islands
(Moore, 1968). Several small patches of flowering Cardamine were also
associated. A second single Apium plant grew on the north wall, about 3 m
above the beach at the base of ‘The Hole’. This is almost certainly the
‘umbellifer’ recorded in 1962 and reported by Strange (1965a), who, in fact,
identified it as such in an earlier manuscript.
No plant resembling the ‘small blue flower’ or ‘composite’ referred to by
Strange (1965a) was seen, nor is it possible to speculate what such observations
may have been. The latter was described by the naval party (unpublished
report) as “a large daisy-like flower” and noted to be “quite common in patches
and seemed to be growing where there was shorter grass. . . . Also the ground
where the flowers were growing seemed to be damper.”
Almost certainly the three forb species have been brought to the island on the
feet or feathers of birds travelling from other more diversely vegetated islands off
the Falkland Islands or the coastal mainland itself. The main Cardamine and
Callitriche site is adjacent to a large black browed albatross colony, while the
Apium site in ‘The Hole’ is surrounded by Wilson’s storm petrel nest burrows.
Other petrels and caracaras may frequently make the crossing, as may
passerines such as tussock birds and the seed-eating black chinned siskin.
Bryophytes
Bryophytes were rare on the island and found mainly on moist, often deeply
shaded, peat in the inter-tussock ‘corridors’ and on moist eroding mounds of
former tussock pedestals beneath the grass canopy (Fig. 6). No epipetric
bryophytes were noted in any rock habitat. Only four moss and five liverwort
species were recorded. The most frequently occurring species was the liverwort
Lophocolea lenta which grew around the moist shaded bases of occasional tussock
pedestals and on inter-tussock mounds, forming thin mats rarely exceeding
1 m2. Lophocolea divaricata, Clasmatocolea vermicularis and Telaranea pseudozoopsis
were occasionally associated. Lophocolea leptantha was noted on drier tussock litter
near the top of ‘The Hole’. Mosses were nowhere common but the cosmopolitan
B y u m pseudotriquetrum was the most frequent, forming very short turves up to
200 cm2; several colonies were found with the remains of previous year’s
sporophytes and young setae of the current year. This was the only fertile
bryophyte encountered. In a very few areas of wet shaded peat, particularly
close to the pond, Calyptrochaete apiculata formed dark green stands of a few
hundred square centimetres usually with Lophocolea spp. associated. In a few
localities, where the canopy was more open, dry peat around the base of tussock
plants and eroded former pedestals, was colonized by Campylopus cf. modestus
which formed short turves of up to 500-700 cm2. This moss was most frequently
recorded near the tussock margin at the northeast of the island where it
occurred with Bryum pseudotriquetrum and Lophocolea sp. A small stand of
T H E NAI’URAL HISTORY OF BEAUCHENE ISLAND
243
Figurr 6 . Mat of bryophytes in tussac ‘corridor’. T h e peat is kept free of litter by the action of a
sprries of petrel which has its nest burrow at left centre. Knife in foreground is 10 crn long.
bryophytes near the top of ‘The Hole’ was the most complex ‘community’ seen
on the island, containing C. cf. modestus, C. introjlexus (the rarest of the
bryophytes found), Lophocolea leptantha and L. divaricata. All the moss species are
widespread in the Falkland Islands with C. upiculuta being the least common.
Lichens
Lichens are the most diverse plant life-form on the island with 12 taxa
recorded, eight of which were noted only as lithophytes, three only as
corticolous species growing on stranded timber, and one occupying both habitat
types. Locally, lichen cover was quite extensive on rock slabs, cliff faces (mainly
from ‘Blinn’s Bay’* southward) and boulder beaches on the west coast, all
beyond the zone of normal wave action. There were no terricolous or littercolonizing species. Six genera are represented, 1 1 taxa having a crustose growthform and one having a foliose growth-form (Mustodia tesselata). No fruticose
*This and several other unoficial place names, wcrc proposed by Strange (1976a).
244
K. I . L. SMITH AND P. A. PRINCE
species were seen, which was surprising since Ramalina terebrata is a common
lichen of coastal rocks around the Falkland Islands. Apart from PoaJlabellata, the
lichens were the only plants that occurred in sufficient abundance to develop
distinctive communities.
The most abundant and widespread community was dominated by Caloplaca
sublobulata, especially on the large rounded boulders of the storm beaches in the
northwest corner and waist of the west coast and on rocks and cliffs around
‘Blinn’s Bay’. It was commonly associated with Buellia coniops, Caloplaca
cirrochrooides, Lecanora cf. lavae, Mastodia tesselata and Verrucaria durietzii. These
lichen stands are clearly visible from a considerable distance due to the
dominance of the brilliant orange C. sublobulata. Rock slabs from the
supralittorial to well inland were frequently covered with black Verrucaria
ceuthocarpa and V. maura and, in the more inland habitats to the summit of ‘The
Citadel’, the grey V. durietzii was often dominant. Pools of clear brackish water,
derived mainly from rain water but occasionally inundated with far-blown sea
spray, in depressions in rock platforms in the lower areas of the southern part of
the island, were often encircled by a narrow zone of greenish-black V. mucosa
(Fig. 7 ) . Such pools overflowed when they reached a certain depth and the very
even lower margin of the Verrucaria zone coincided exactly with the level of the
maximum depth the pool could attain, i.e. the lichen could not become
submerged. Immediately below the lichen zone was a band of filamentous green
algae (possibly Enteromorpha) attached to the rock, which sometimes covered the
floor of the shallow pools.
O n more sheltered rock surfaces, Mastodia tesselata formed closed pure stands
up to several square metres, notably around ‘Blinn’s Bay’. These sometimes
merged into stands dominated by C. sublobulata, although they were frequently
Figure 7 . Lichen zonation around a small supralittoral rock pool. Black outer zone is Verrucaria
mucosa and dark central zone is an alga (?Enterornorpha);other algae occur in the intermediate zone.
Hammer is 30 cm long.
THE NATURAL HISTORY OF BEAUCHENE ISLAND
245
sharply demarcated from eath other. It was quite common as scattered thalli up
to 75 m altitude at the south end of the island. In places where the substrate was
periodically inundated by spray or rain water, the drainage area was dominated
by Prasiola crispa and plants between the Prasiola and Mastodia stands showed
intermediate characters. This form, intermediate between the alga and its
lichenized form (Mastodia) is also quite common on Signy Island, South Orkney
Islands (R.I.L.S., unpublished data).
Stranded timber, mainly trunks of Nothofagus spp. (see below) of southern
South American provenance, and some ship-borne timbers, were frequent on
the two west coast boulder beaches. These timbers formed an alien substrate,
which was colonized by a group of corticolous lichens, dominated by Caloplaca
sublobulata, with Arthropyrenia sp., Buellia punctata and Lecanora subfusca agg.
associated sparsely.
Algae
Of the terrestrial macroalgae only Prasiola crispa was observed. This green
foliose alga was most common in drainage channels on rock surfaces, often
associated with Mastodia tesselata (see above), and around the rockier bird
nesting areas. Elsewhere it was occasionally seen on damp eroded peat in
openings amongs the tussock grass. Also, on many of the damper and more
shaded areas of seal-eroded peat beneath the tussac canopy, filamentous green
algae (predominantly a species of Oedocladium) formed mats, often associated
with the liverworts Lophocolea spp. and small quantities of blue-green algae. Dry
eroded faces of peat were locally colonized by lime-green to yellowish, powdery,
unicellular algae including Ankistrodesmus sp. and Hazenia sp. The shaded damp
underside of stones and rock slabs at the south end of the island were usually
colonized by unicellular green alga, while chasmolithic or possibly endolithic
blue-green algae were common below the translucent surface layer of the
granular quartzite rock. The dead dry bases of tussac leaves were commonly
colonized by a powdery unicellular green alga.
Marine algae
The sublittoral sloping shoreline of the northern part of the west coast, north
coast and the coves and bays of the southwest and southeast is dominated by
dense stands of the very large kelps Durvillea antarctica and Lessonia antarctica,
while Macrocystis pyriformis predominated a little offshore, especially in the coves
and bays. Throughout the littoral and sublittoral zones numerous green, red
and brown taxa were common and in the inter-tidal pools a pink calcareous
encrusting alga predominated. This alga and some brown species grew in the
supralittoral zone up to about 30 m above high water mark on the vertical cliffs
of the high southern part of the island, which are lashed by massive waves
during southerly storms.
Fungi
Only two species of basidiomycete fungi were found. Panaeolus subbalteatus was
growing on moist tussac litter near the freshwater pool and at the northeast
246
R . I . L. SMITH AND P. A. PRINCE
corner of the island. At the latter site the largest toadstools had a cap diameter
of 8 cm and stipe length also of 8 cm. Coprinus hemerobius was recorded at the base
of the crown of a tussac plant above ‘Blinn’s Bay’. It is to be expected that
several other taxa would develop basidiocarps later in the summer when
conditions probably become wetter. Certainly, tussock grass litter on the wetter
and colder South Georgia possesses a remarkably rich higher fungi flora
(R.I.L.S., unpublished data). The live leaves of Poa Jabellata on BeauchCne
Island were abundantly infected with a dematiaceous deuteromycete
(Cladosporium cladosporioides ss. lato) which forms elongated black perithecia on
the foliage; small hemispherical black perithecia were also quite abundant on
dead attached leaves and culms. A rust, probably Puccinia striiformis and/or
P. brachypodi var. poae-nemoralis, was occasionally present on live tussac leaves.
Gunn (1974) noted the incidence of rust on P. Jubellata on the Falkland Islands
to be minimal where the grass was influenced by penguins, albatrosses and seals,
attributing this to the increased vigour of the plants caused by the high N and P
concentrations in the soil.
MICROBIOLOGY
A preliminary study of the microbiological composition of tussac peat was
undertaken on samples of compressed aerobic peat between P. Jabellata tussocks,
occasionally frequented by sea lions, above ‘Blinn’s Bay’. The peat was partly
covered with Lophocolea spp. The peat was strongly acidic and the pH ( 1 : 1
dilution) down the profile was 3.8 (0-1 cm depth), 4.0 (1-3 cm depth) and 3.9
at 3-6, 6-9 and 9-12 cm depths. Ten-gram fresh samples, collected aseptically,
were hand-shaken with 90 ml 0.1yo peptone water diluent. After further
dilution, the homogenates were spread-plated in triplicate on casein peptone
starch agar amended with Actidione (50 mg 1 - ’ ) and Sabouraud dextrose agar
amended with Aureomycin (30 mg 1 - I ) (Wynn-Williams, 1979). After
incubation at 10°C for 14 days the number of viable organisms in terms of
colony-forming units was determined.
The viable counts of various microbial populations are summarized in
Table 3. Although the total heterotrophic bacterial population declined with
increasing depth, the chromogenic population remained high. The purple
Table 3. Viable microbial populations in tussac peat on BeauchCne Island
Mean number of colony-forming units
x lo9 g - l fresh wtks.E.
Microbial group
Total chromogenic bacteria
Chromobacterium sp.
Actinomycetes
Total heterotrophic bacteria
Total yeasts
Mucorales
Penicillium spp.
Total hyphal fungi
Depth 0-1 cm
2500 f450
0.6 f0.3
100f90
> 5000 k 500
430+155
2 3 k 14
43& 16
140+80
Depth 1-3 cm
2250 k 500
0.3k0.2
2 2 5 13
2900 f650
245k 140
0.8k0.4
1.350.5
22k 16
T H E NATURAL HISTORY OF BEAUCHENE ISLAND
247
pigmented Chromobacterium was detected, sharing the acid tolerance of subAntarctic organic soils where it has been detected at South Georgia
(pH 3.7-4.0) (Wynn-Williams, 1983). This distinguished it from the less acidtolerant strains from the maritime Antarctic (pH > 4.5). Actinomycetes are
common in temperate soils but their occurrence in the sub-Antarctic and
Antarctic is much less frequent (Boyd, Staley & Boyd, 1966). The yeast
population was about ten times higher than in Polytrichum alpestre peat at Signy
Island, South Orkney Islands (Wynn-Williams, 1980). This was probably due to
the higher nutrient status and warmer conditions on BeauchCne Island. The
counts of hyphal fungal colony-forming units were, however, very similar to
those at Signy Island, possibly reflecting fungal adaptability to available
nutrients and climatic conditions in the latter instance. Nevertheless, the
occurrence of Penicillium spp. in the BeauchCne Island peat, was in contrast to the
Antarctic peat of Signy Island where it had not been detected, although it was
isolated from similar sub-Antarctic peat at South Georgia.
TUSSOCK GRASS
As on most of the ungrazed islands around the Falkland Islands, tussock grass
or tussac (Poa jlabellata) dominates the island’s vegetation, covering about 600/,
of its area (1 13 ha). The tussac ecosystem is closely comparable with a forest of
evergreen trees, which produces a dense canopy and has virtually no field layer
other than litter. Since the total area of ground flora in this ecosystem amounts
to little more than a few dozen square metres, the community may be regarded
as monospecific. Such a terrestrial phanerogamic community is exceptional in
the world’s vegetation.
Over most of the island the grass reaches exceptional dimensions (Fig. 8A).
Individual plants are typically about 3 m high (maximum measured was 3.5 m)
which includes a peaty pedestal, commonly about 1.0-1.5 m high and 2 m in
diameter, and have a canopy up to 4.5 m across. In large plants tillers were
frequently up to 2 m in length, with the maximum measured being 2.15 m. The
canopy consists of an upper crown of up to several thousand living tillers, the
leaves of which remain green for about two years, and a lower skirt of attached
dead foliage extending laterally 1.0-1.5 m beyond the pedestal. The skirts of
adjacent plants are interlaced and inseparable. Beneath the skirt and between
pedestals, a network of interconnecting tunnels, carpeted with detached tussock
litter, ramifies throughout the grass ‘forest’. Towards the periphery of this
vegetation, these tunnels are frequently traversed by rockhopper penguins and
sea lions. Human penetration into the grassland is possible either by crawling
through the dark damp maze of tunnels or, often more rapidly but more
strenuously, by jumping from crown to crown about 2 m above the ground.
Throughout much of this closed vegetation over the island there may be as
few as 600-700 plants h a - ’ . These massive plants must be of considerable age
and a radiocarbon date obtained from the centre of the base of a 75 cm high
pedestal with healthy roots was 290f40 years B.P. (see Table 6).
Many plants had not produced flowers, but those towards the margin of the
grassland often did so in profusion. In mid-December these inflorescences were
dead and had shed much of their seed. It was estimated that anthesis and seed
set occurred during October. Because of the large size of the inflorescences, they
248
R. I. L. SMITH AND P. A. PRINCE
Figure 8. Tussock grass (Poajlabchzta). (A) Typical tall growth-form which covers much of the
island c. 3 m tall: (B) dwarf growth-form, c. 15 crn tall, on exposed rock platforms.
T H E NATURAL HISTORY OF BEAUCHENE ISLAND
249
are almost certainly formed during the previous summer and development
continues during winter. O n South Georgia, inflorescences develop as early as
the previous December-January but remain ensheathed and dormant during
winter. They develop rapidly between September and November-December
when they are mature and anthesis occurs (Walton, 1982). Seedlings are
abundant in areas of recolonization, such as erosion scars where peatslips have
occurred above cliffs on the east coast (e.g. above ‘Blinn’s Bay’) and in gaps
within the tussock ‘forest’ where an old plant has died and the pedestal eroded;
colonization occurs on suitably moist peat accumulated along the margin of the
grassland. Most small seedlings growing in association with the patches of
bryophytes were unsuccessful as few plants developed beyond three or four
leaves.
O n the sub-Antarctic island of South Georgia Poa jlabellata occurs as two
distinctive phenotypes. One has a robust (up to 1.5 m), luxuriant growth form
with broad dark green leaves and grows in nitrogen-enriched areas influenced
by elephant and fur seal activity and seabird colonies. The other produces
shorter (up to 0.75 m) plants with narrow pale yellow-green leaves and grows
on non-enriched drier substrates (Gunn, 1976; Walton & Smith, 1980; Jellings,
Usher & Leech, 1983). Similarly, the morphology of tussac on Beauchhe Island
varies considerably with a relatively narrow leaved form being the most typical.
It may be that there are several genotypes co-existing on the island. Most of the
tussock vegetation is subjected to the same degree of exposure and deposition of
volatilized nitrogenous compounds from the surrounding seabird colonies.
However, adjacent plants often exhibit variation that seems too large to be
attributed to environmental differences. Two such plants growing above ‘Blinn’s
Bay’, only 0.5 m apart, were compared morphologically (Table 4). Both were of
the same size and stature and presumably were of similar age.
Elsewhere, typical very tall tussac plants had inflorescences of about half to
three-quarters the length of the longest leaves but the panicles varied
considerably (Fig. 9A-E). Most were about 15-20 cm in length and shortly
branched approaching a raceme, producing a dense mass of spikelets about
1.5-2.0 cm wide. However, much shorter bushier panicles, 6-10 cm long and
3-4cm broad and borne on short robust culms were not infrequent. At the
other extreme but equally frequent were long, slender, sparsely branched
Table 4. Morphological differences between two adjacent mature Poa jlabellata
plants. (Data are means of 10 tillers or inflorescences)
Parameter
Length of longest (oldest) leaf per tiller (cm)
Number of green leaves per tiller
Number of white (ensheathed) leaves > 5 mm per tiller
Maximum width of longest leaves (mm)
Bright purple pigmentation in leaf sheaths and tiller bases
Crinkling of lamina 3/4 way along leaf
Length of panirle ( r m )
Length of rulm (excluding panirle) (cm)
Number of inflorescences (entire plant)
Narrow leaved
phenotype
Broad leaved
phenotype
I29
8
3
12
Yes
No
9
53
62
143
II
4
25
No
Yes
20
78
36
250
R. I. L. SMITH AND P. A. PRINCE
Figure 9. Variation in tussock grass panicles. (A)-(D) from large plants.
THE NATURAL HISTORY O F BEAUCHENE ISLAND
25 1
Figure 9. Variation in tussock grass panicles. ( E ) from dwarf plants (entire tillers).
panicles or racemes of 30-40 cm length (maximum measured was 41.5 cm)
borne on long lax culms. A single 20 cm panicle was dissected and yielded just
over 5000 seeds. Such plants had over 100 inflorescences.
A narrow-leaved dwarf genotype resembling Poa alopecurus exists in an area of
extremely windswept rock slabs at about 20-25 m altitude towards the south
end of the island (Fig. 8B). These diminutive plants are rooted in small fissures
with very small amounts of mineral soil. They ranged from 10 to 50 cm tall. All
had a dense bushy mass of tillers and produced no peaty pedestal; the small
amount of standing dead foliage and absence of litter was probably due to
removal by strong winds. All produced very large numbers of inflorescences,
indicating that even the smallest plants were mature. Dissection of several small
plants, barely 15-20 cm across, revealed that the leaves were often only 3-5 cm
long. While most inflorescences at the edge of the plants were taller and dead (in
mid-December), those towards the centre were only beginning to emerge; those
in an intermediate position were in anthesis, indicating at least a month’s
difference in flowering time within a single plant. In the smallest of the panicles
(Fig. 9E), only 15-25 seeds were produced.
The only substantial stand of tussac at the southern end of the island occurred
on sandy, quartzite-derived, mineral soil overlying sloping rock terraces on the
northeast side of the fault. Like the dwarf tussac, these plants were narrowleaved, yellowish-green in colour and produced a profusion of inflorescences.
The plants were about 75 cm high but had accumulated little litter and
virtually no peat beneath the canopy. Elsewhere there were a few plants of
similar stature on precipitous ledges on the extreme southeast cliffs and on the
southwest.
The thermal environment of tussock grass presents a very favourable series of
252
R. I. L. SMITH A N D P. A. PRINCE
Table 5 . Temperatures ("C) recorded in a tussac plant in contrasting weather
conditions
Full
Position where temperature recorded
Air temperature (shade)
Inter-tussock space
'l'ussac crown:
amongst foliage
base of tillers
mid-leaf, upper surface
lower surface
'l'ussac skirt:
outer (5 cm depth)
inner (35 cm depth)
Ground litter:
surface
peat/littrr interface (2-3 cm below surface)
sunshine,
calm
Overcast,
calm
____
~.
~
-
8.3
5.2
16.0
5.6
16.6
7.3
8.5
Overcast,
strong
wind
~
~~
5.3
5.6
5.1
8.8
6.2
6.2
11.1
24.8
20.3
9.4
22.3
13.3
10.4
8. I
9.4
28.6
21.0
10.8
6.6
9.6
9.3
8.8
8.3
niches for the invertebrate fauna. The straw-like nature of the skirt affords
efficient insulation against low temperatures and wind, while the downward
alignment of this material serves as a waterproof thatching for the interior of the
skirt. Temperatures recorded in various positions in a tussock plant above
'Blinn's Bay' at about 14.00 hours on three contrasting days are presented in
Table 5 . During calm sunny periods, relatively high temperature are reached
and maintained in the skirt and ground litter well into the evening, while in
overcast weather temperatures remain low, especially if there is a strong wind.
PEAT DEPOSITS
A remarkable feature of Beauchtne Island is the accumulation of peat
beneath the tussock grass. Along about one-third of the windward margin of
grassland, adjacent to the mixed albatross and penguin colony, this organic
deposit has been eroded to form a steep, often vertical peat face (Fig. 10). In
several places this face exceeds lOm in height and the maximum height
measured, at a point midway along the western tussac margin, was 13.25 m. It
is not known if such a depth is maintained over most of the vegetated area, but
a small erosion scar at the northeastern corner of the island indicated that the
peat there is at least 5 m deep. Along stretches of the western tussac margin the
peat edge has slumped, causing a discontinuity in the vegetation. Aerial
photographs reveal occasional narrow shallow 'valleys' extending from the
margin towards the higher interior.
The formation of this peat is unusual since accumulations of organic matter
typically form under wet conditions, both climatically and topographically, in
depressions and rock basins with impeded drainage. However, neither of these
conditions prevail on Beauchtne Island, the amount of precipitation being
relatively low and the peat forming as a mound on top of a level, well-drained,
rock surface. Such accumulations are typical of the moss bank peat deposits of
the northern maritime Antarctic (Smith, 1979; Fenton & Smith, 1982). The
'I'HE NATURAL HISTORY OF BEAUCHENE ISLAND
253
Tussac
qrossland
Tussac
Erodinq
Eroding
peat cliff
Peat
Penguin
and
Penguin
and
Peat
a1batross
Figure 10. Schematic diagram of two stages of peat cliff at the western margin of tussac grassland
adjacent to the main penguin and albatross colony.
considerable depth of peat on the island, formed solely from Poa jlabellata litter,
poses an interesting question. No similar organic deposits have been reported in
the Falkland Islands, where depths of peat seldom exceed 5 m and these occur
mainly under Cortaderia pilosa grassland or Empetrum rubrum heath, although many
of the smaller islands have deep peat beneath tussac grassland but rarely more
than about 5 m in depth. The oldest radiocarbon date for a Falkland Islands
basal peat deposit (1.6 m deep) is 9280+260 years B.P. at a site near Port
Howard, West Falkland Island (Barrow, 1978). This, together with information
available on the glacial history of the islands (e.g. Clapperton, 1971), suggested
that the great depth of peat on Beauchhe Island accumulated because the
island avoided glaciation and that the basal deposits may pre-date anything on
the Falkland Islands.
A site was chosen about 600 m from the southern end of the tussock grassland
for obtaining uncontaminated samples for radiocarbon dating. The depth of
peat from the base of the cap of live tussac pedestals to the bedrock was 11.25 m,
but the eroded face was not vertical (Fig. 11A); the pedestals contributed a
further 0.5 to 1.0 m of peat on the surface. An attempt to sample the peat using
a Hiller corer was unsuccessful due to the dry and friable nature of the material.
Samples were taken at intervals down the profile from pits dug about 1 m into
the peat face to ensure no contemporaneous material, either by wind impaction
or slumping from above. The lowermost samples had to be obtained by digging
a vertical pit since 1.4 m of compacted peat debris lay at the foot of the face.
The deposit overlying the bedrock was a yellow-grey clay, itself overlain by a
reddish-brown waterlogged peat. From about 50 cm to 1.50 m was a band of
rock-hard black peat (Fig. 11B) (see below) and from about 1.50 m to near the
surface the peat was amorphous but contained clearly recognizable tussac leaves
compressed horizontally; leaf fragments were also distinctly preserved to the
base of the profile. In the upper 50 cm of peat were the remains of dead roots
and leaves. Live roots were present only within the pedestal of each live tussac
plant. pH, field water content, loss of ignition and bulk density obtained from
the cores taken for radiocarbon dating are presented in Table 6. Throughout
the profile, arthropod remains were abundant, particularly the exoskeletons of
beetles (mainly elytra), and occasional spiders, flies and mites. In some samples
examined, as many as ten small elytra per square centimetre were not
uncommon in layers of peat only 1 mm apart. Seal hairs (see below) were also
1
Figure I I . Site from which peat samples were collected for analysis, adjacent to the main black
browed albatross and rockhopper penguin colony on the mid-west side of Beauchene Island.
(A) Eroding peat face (pole is 2.80 m long). (B) Base of peat profile from bedrock to 2.25 m above
i t (from lower left hand area of Fig. I IA).
THE NATURAL HISTORY OF BEAUCHENE ISLAND
255
Table 6. Radiocarbon dates and other analyses for peat samples in 11.25 m deep
profile on Beauchihe Island
Depth
(m)
Radiocarbon age
(yr. B.P.) and analysis
number
n=l
0.75
1.25
3.25
3.75
7.00
7.50
9.75
10.25
10.75
11.00
11.25
290540
540 k 40
I620 40
2190k40
3830 40
4200+50
7030k50
7660550
9560 k 50
I1570+50
I1300+80
(SRR-1987)
(SRR-1988)
(SRR-1989)
(SRR-1990)
(SRR-1991)
(SRR-1992)
(SRR-1993)
(SRR-1994)
(SRR-1995)
(SRR-1996)
(SRR-1997)
Corrected
radiocarbon
age
(yr B.P.)*
Bulk
density
(g cm-Y
n = 10
360
545
I580
2315
4300
4860
7870
8510
I0550
I2500
12210
0.36
0.73
0.75
0.76
0.85
0.94
1.17
1.09
I .09
1.21
I .45
n = 5-10
Field
moisture
content
(%
drylwt)
n = l
PH
n=2
94.9
91.9
92.2
92.8
89.5
89.2
90.2
90.3
91.6
90.7
10.4
348
260
285
33 I
254
246
I98
210
206
226
44
3.25
5.72
4.02
4.55
6.14
6.47
5.90
6.07
6.01
6.43
7.09
Loss on
ignition
(% dry W t )
Additional radiocarbon dates for lignitic samples at 9.5-10.0 m depth at a site about 200 m north of the
main site: 6850+55 (SRR-1171) ( = 7700 corr.), 7190k50 (SRR-1172) ( = 8040 corr.) and 8130k45 (SRR1 170) ( = 9000 corr.).
*Derived from Clark (1975).
sometimes quite frequent at some levels and a single hair was isolated from the
basal layer of clay in which tussac root and leaf fragments were also frequent.
The radiocarbon dates indicate relatively rapid accumulation of peat from
about 9 m depth until the present, while from 9 to 11 m accumulation was
apparently much slower. For both periods, there is an almost linear relationship
between age and depth with a sharp transition occurring around 5000 years B.P.
( = c. 5785 years B . P . corrected; see Clark, 1975). The age of the basal peat (and
of the slightly younger root fragments contained in the underlying clay)
predates the oldest from the Falklands Islands by about 2000 years, but this
does not positively confirm that the island escaped the Falklands glacial epoch
(which ended around 12 000 to 1 1 000 years ago) and remained a refugium for
the biota of the archipelago.
The position of this transition may be particularly significant in the climatic
history of the Magellanic region and possibly the southern hemisphere as a
whole. The age-depth transition marks the upper level of the exceptionally hard
black lignitic peat, which appears to have been formed under relatively wet
conditions, allowing more rapid decomposition or compaction, or both, thereby
compressing the lower 6500 years’ accumulation into only 2 m depth. This
material has an unusually high bulk density for a peat. The upper 9 m of more
fibrous brown, yet very compact, peat is slightly less dense and may have been
formed under drier conditions. The organic content (as loss on ignition) varied
little throughout the profile and, while there is a strong correlation ( r = 0.95)
between bulk density and age, there is none between bulk density and L.O.I.
( r = -0.46) for the levels between 1.25 and 11 m. The transition coincides very
closely with that of a major climatic change throughout the southern
hemisphere. The period between the end of the last major glaciation, when the
14
256
R. I . L. SMITH AND P. A. PRINCE
climate first became warmer than it is today, until the time when it became
colder, was the Postglacial or Hypsithermal Interval which in Chilean
Patagonia lasted from around 11 000 to 5000 years B.P. (Mercer, 1970). Heusser
& Streeter (1980) have shown that, during this period, mean annual
precipitation was high between about 11 000 and 9000 years B.P., thereafter
decreasing until about 7000 years B.P. Temperatures then decreased and
marked the commencement of the relatively brief First Neoglacial re-advance
when a colder drier climate prevailed. A similar chronology has been detected
from palynological studies on Iles Kerguelen (Young & Schofield, 1973) and
South Georgia (Barrow, 1983). It would seem, therefore, that the transition to a
rock-hard form of peat on BeauchCne Island represents the end of the relatively
warm and wet Hypsithermal Interval and the beginning of the First Neoglacial
maximum, when conditions were colder and drier. When the BeauchCne Island
peat age data are transformed to the log scale and plotted against depth, there is
a break in slope at about 2000 years B.P. ( = 1950 years B.P. corrected); this date
approaches that of the Second Neoglacial readvance (Mercer, 1970, 1978). A
more detailed analysis of this unique peat deposit may even reveal the Third
Neoglacial readvance or 'Little Ice Age' of c. 100-300 years ago.
In a more detailed analysis of the Beauchhe Island peat, Smith & Clymo
(1984) determined that the age u. depth profile is consistent with a constant
proportional rate of decay in the peat and a constant rate of addition of dry
matter to the peat. The rate of decay is within the range for peat in
corresponding latitudes in the northern hemisphere, but the rate of addition is
about ten times as great. This difference may be partly attributable to the plant
species and partly to nutritional differences resulting from the presence of
nesting seabirds.
Lignitic peat
The blackish layer of compressed rock-hard peat near the base of the eroded
peat faces, which breaks with a conchoidal fracture, was first reported by
Strange (1976a) and merited a detailed study. However, its hardness appeared
to be largely caused by exposure to air since the moisture content of this
material was barely 30% (dry weight) compared with around 200% where it
had a hard cheesy texture about 1 m into the peat face. The material'bears some
characteristics of a peat but other features resemble a lignite or brown coal, both
macroscopically and microscopically, and it represents an intermediate stage in
the peat to lignite transition. It is composed primarily of densinite, a compacted
and gelified variant of humodetrinite. This homogeneous sediment contains no
identifiable plant fragments. The hardness and compaction was probably caused
by a combination of biogeochemical gelification of the fine organic debris and
the ground water regime. However, there is no evidence of alteration due to
geothermal heat, which is characteristic of true lignite. Also, this material is only
8000-9000 years old, a factor of several thousand years too young for true
lignite; similar transitional organic sediments from other parts of the world are
about one million years old (J. D. Yeakel, in hit.). A white crust of gypsum,
determined by X-ray diffraction, occurred on portions of the material. Material
older than about 9000 years remained beneath the base of the erosion scar and
was not exposed to the atmosphere; it was comparatively wet and had a soft
cheese-like texture.
THE NATURAL HISTORY OF BEAUCHENE ISLAND
257
Doctor F. J. Rich’s (in lilt.) analysis of this material indicated that it
contained a large quantity of alkali soluble humic material and is composed of
fragments of vascular tissue, cuticle, trichomes, fungal hyphae and spores, and
pollen grains, predominantly of Gramineae (presumably Poa JEabellata), but
Compositae grains were also isolated. The vascular elements contained no
cellulose and the great abundance of fungal material suggests that the fungi may
have been cellulolytic and most likely were the principal agents in the
humification process of the peat. Alkali soluble, humic substances are derived in
part by the breakdown of cellulose. Doctor Rich concludes: “The results will be
of great interest to people who are concerned with coal formation. Beauchtne
Island is an unlikely place to establish a paradigm for coal formation, but this
highly altered peat is so similar to a coal superficially, and yet has evidently
been subjected to only chemical and biological alteration.”
Chemical analysis of peat
The vegetation is frequently deluged with sea spray and is continually being
enriched by the nitrogenous aerosol drifting over the island from the huge bird
colonies on the west, south and north-east. An analysis of surface peat in which
healthy colonizing Poa Jlabellata seedlings with several tillers were growing is
given in Table 7. Additional chemical data are presented for tussac leaves and
pedestal peat (i.e. the root environment of mature plants) together with some
comparable data from South Georgia. The peat in which seedlings become
established has exceptionally high concentrations of most elements, notably total
and extractable N, and extractable P, Ca and Mg, as do the leaves of the
mature plant sampled. The chemical status of the substratum is probably the
principal reason for the extremely high production and biomass of tussac on the
island. Corresponding data for intensively seal-influenced tussac peat on South
Georgia are much lower, suggesting that the input of volatilized nitrogenous
compounds from seabirds is considerably greater than the direct input by seals.
Analysis of a sample of the lignitic peat yielded the following results (as o/o dry
wt): C (51.00), H (4.63), N (3.33), S (2.96), ash (11.48), 0 (26.60, by
difference); the ash comprised (as yo):SO, (26.4), Na,O (21.8), C a O (12.3),
MgO (11.8), SiO, (10.2), A1,0, (4.8), P,O, (3.1), K,O (2.4), Fe,O, (1.3),
TiO, (0.4), MnO (0.01), residue (5.5). The calorific value was 9514.4 kJ,
considerably higher than that ofordinary peat (e.g. 6041.3 kJ for Irish peat and
8229.5 kJ for Falkland Islands peat-see Dunstan, 1939).
STRANDED TREES
The storm beach on the west coast of the waist of the island is littered with
driftwood and man-made flotsam, cast up by strong westerly gales. Some of the
timber is obviously derived from ships, having been shaped and often bearing
saw cuts and sometimes nails. However, the majority of the logs are of irregular
shape, have retained their bark and often bear a broader bole or parts of
branches. Most lie along the margin of the tussock vegetation, about 10-12 m
above high water mark and 50 m inland (Fig. 12); some lie beyond the tussock
margin partially buried by grass peat. Similar flotsam, including tree trunks,
occur on the smaller storm beach at the northwest of the island and
Table 7. Chemical analysis of tussac peat and leaves from Beauchtne Island and South Georgia
Loss on
ignition
(9.0 dry wt) pH
Sample details
Extractable (mg 100 g - ’ dry wt)
Na
K
Ca
Mg
Mn
Fe
Al
PO,-P
Total
NO,+NO,-N
NH,-N
(“lodry
wt)
N
P
Na
K
Ca Mg
-
~
SurfDe peat at margin of eroding peat f a e with
colonizing Poa flabellata, Beauchh Island
South end of main albatross and penguin
colony, west side of island
Southeast end of main albatross and penguin
colony, west side of island
Adjacent to albatross and penguin colony,
southeast side of island
Material associated with a single mature Poa
flabellata tussock, ‘Blinn’s Bay’, B e a u c k Island
Centre of ‘live’ pedestal (50 cm depth)*
Peat under litter beneath tussac skirt (2-5 cm
depth)
Seal-eroded former pedestal adjacent to
previous sample (5-10 cm depth)
Live mature leaves (mid-lamina)*
Comparable material associated with mature Poa
flabellata tussocks, South Georgia
Non-seal influenced pedestal (5-10 cm
depth), King Edward Point, Cumberland
East Bay
Peat under litter beneath tussac skirt (2-5 cm
depth), Freshwater Cove, Bird Island
Seal-eroded pedestal (5-10 cm depth),
Freshwater Cove, Bird Island
Live mature leaves (mid-lamina) from sealaffected plant, Freshwater Cove, Bird
Island
88
3.7
350
9
220
100
0.3
43
69
17
1.1
12
3.5
-
-
-
85
4.0
280
40
680
160
0.4
29
69
250
7.5
38
6.8
-
-
-
78
4.3
300
16
970
140
0.2
190
83
360
5.7
12
3.8
-
-
1400
1100
730
410
78
450
130
210
0.5
0.3
<20
85
<I0
68
58
230
3.4
0.5
24
13
1.1
-
-
-
3.5
-
-
88
-
3500
460
270
390
0.2
<20
15
140
7.4
160
1 . 6 - - - - -
95
-
360
1900
120
85
1.8
t20
<I0
560
0.7
330
2.4
95
3.9
17
19
33
27
-
-
-
12
-
-
2.4
-
-
-
-
96
-
76
82
55
50
0.6
43
32
15
1.o
47
3.6
-
-
-
-
-
97
-
53
48
43
33
0.4
80
29
11
1.4
34
3.6
-
-
-
-
97
-
320
1000
60
100
1.8
<20
I1
160
t0.1
240
3.2
0.6 0.5
1.9 0.1
-
95
78
-
0.6 0.5
~
-
-
-
-
-
-
-
-
-
-
~
1.9 0.1 0.1
*The 2.5 m high plant was unaffected by seals but the adjacent pedestal and ‘tunnel’ beneath the skirt are orcasionally frequented by sea lions: plants on Bird Island are much smaller
and severely trampled by fur seals.
1 H E NATURAL HISTORY OF BEAUCHENE ISLAND
259
occasionally above coves elsewhere. The dense encrustation of lichens on many
of the logs above the main storm beach had the appearance of having been in
situ for a long time. Seven trunks and a branch were examined and samples of
wood taken for identification of tree species. Separate samples were taken from
the outer wood of four trees for radiocarbon dating (Table 8). All trees
appeared to be aged about 50-100 years at the time of felling, but their
radiocarbon ages ranged from 2 10 to 540 years (305-545 years corrected ages),
suggesting that they had been on Beauchkne Island for up to several centuries.
All the trees identified were species of Nothofagus of South American provenance.
SEALS
Fur seals
A brief account of fur seal (Arctocephalus australis) exploitation on BeauchZne
Island up to the early 1900s has been provided by Smith (1984). A seal survey
of‘ the Falkland Islands by Discovery Expeditions in the mid-1930s was unable to
reach Beauchihe Island (Hamilton, 1939) but in March 1936, B. B. Roberts of
the British Graham Land Expedition noted hundreds of fur seals as well as a
number of sea lions in the water about the ship as they passed close to the
island. R. M. Laws carried out a survey of the status of seals in the Falkland
Islands in late summer 1951. Unfortunately, a landing was not possible on
BeauchZne Island due to bad weather. Laws (1951) stated “In addition . . . fur
seals are known to occur in considerable numbers at Beauchhe Island” and “it
is reputed to be the largest rookery in the islands”, but there is no evidence to
Figure 12. Nothofagus trunks stranded for several hundred years along the tussac margin around a
large bay on the west coast of Beauchtne Island.
260
R. I. L. SMITH AND P. A. PRINCE
Table 8. Details of selected stranded trees above storm beach on mid-west coast
of Beauchene Island
I
2
3
4.
5.
6.
7.
8.
Nothofagus pumilio: 3 m inland from the tussac margin. Length 3 m; diameter 16 cm at 30 cm from the
base. Radiocarbon age 540k40 years B.P. (SRR-1975).
N . betuloides: I m inland from the tussac margin. Length 3.85 m; diameter 40 cm near base. Appeared to
have a partially pointed end possibly pared by an axe.
N . obliqua: I rn inland from the tussac margin. Length 10.8 m; diameter 50 cm at 1 m from a spreading
base, 30 cm at 10 m from the base. Radiocarbon age 210f40 years B.P. (SRR-1976).
N . betuloides: At margin of tussac vegetation. Length 4.9 m; diameter 30 cm at 30 cm from base.
N . pumilio: At margin of tussac vegetation. Length 6.8 m; diameter 40 cm near base
N . pumilio: 20 m into the tussac vegetation at the north end of the storm beach. Length 3.75 m; diameter
25 cm (maximum). Radiocarbon age 250k40 years B.P. (SRR-1977).
N . pumilio: as 6. Length 1.5 m; diameter 30 cm (maximum). Radiocarbon age 280f60 years B.P. (SRR1978).
N . obligua: Branch lying above rocks below albatross/penguin colony to north of storm beach. Length
c. 2.5 m; diameter c. 6 cm.
support this. A further seal survey was achieved in 1965 by Strange (1979), but
again no landing was possible on Beauchihe Island. However, during several
visits between 1963 and 1972 he saw no fur seals. This was confirmed by
R.I.L.S. in March 1977 and during the present survey period.
There is an historical record of fur seals on the island contained in the peat
deposits. Seal hairs are frequently encountered in the peat profile and, while
compressed flat, they can be determined microscopically as belonging to either
fur seals or to sea lions according to the hair pattern key provided by Scheffer
(1964). Both guard and underhairs are present (the latter are sparse on sea
lions) and occur to the base of the deposits described above. For example, a
c. 25 cm2 sample of peat taken from 7 m depth yielded four hairs with a medulla
and a diameter ranging from 144 to 231 pm (diagnostic of fur seal guard hairs)
and four hairs with no medulla and a diameter of 18 to 66 pm (diagnostic of sea
lion hairs). Radiocarbon dating of various levels from which hairs were isolated
indicated that fur seals occurred on the island for approximately 11 000 years,
but were virtually exterminated within a few decades in the late eighteenth and
early nineteenth centuries.
Sea lions
Sea lions (OtariuJlauescens) were first reported on Beauchihe Island by a naval
party (unpublished report) who counted 150, including three pups, in December
1962 towards the south end of the island and c. 50 during a visit in December
1963. However, in December 1964, Strange (1965a) counted 400-500 with the
main concentration in the north and northwest (but given as northeast) of the
island and, although no pups were seen, Strange concluded that the species does
breed in small numbers. During the 1980 survey, small numbers of mainly
immature bulls were observed on rocks and offshore along the north, west and
southeast coasts and also in the grassland up to 100 m from the tussac margin.
The main concentration of 40-50 was at the northwest corner of the island.
Here an extensive area of tussac has been killed and the pedestals eroded, often
remaining as fibrous pillars up to 2 m high. Such damage suggested a possible
THE NATURAL HISTORY OF BEAUCHENE ISLAND
26 1
breeding site although no pups were seen anywhere during the 1980 survey.
Lesser damage to tussac by sea lions was noted in several places, notably above
‘Blinn’s Bay’.
O n two occasions R.I.L.S. witnessed aggression by mature bull sea lions
towards rockhopper penguins. In one instance a seal awoke and suddenly
lunged at and killed one of a group of penguins passing close by; in another
instance a sea lion attacked and killed a penguin in the water in ‘Blinn’s Bay’.
On several occasions penguin skins were seen lying on the shoreline, presumably
the victims of similar attacks.
Other seals
Elephant seals (Mirounga leonina) were generally scarce with most occurrences
(15) on the rocky shore of the north coast. These were all immature bulls. A
single leopard seal (Hydrurga leptonyx) was seen on two consecutive days lying on
intertidal kelp on a rock platform.
BIRDS
The birds discussed in the following account are described in more detail by
Woods (1975, 1982). A list of species seen and their probable status on the island
is given in Table 9.
The outstanding feature of the island’s wildlife is its immense mixed colonies
of black browed albatrosses and rockhopper penguins, occupying almost 20% of
the island’s area on the exposed west, south-east and north-east sides (Figs 13,
14). They are afforded little shelter from the tussac grassland. The importance
of this population was recognized by Strange (1965a, 1965b) and commented
upon by Woods (1966). One of the main aims of the present authors’ survey was
to determine more precisely the number of albatrosses breeding.
Black browed albatrosses
One of the earliest references to the importance of Beauchhe Island as a
breeding site for mollymauks (black browed albatrosses) was given by Vallentin
(1904), and both he and Boyson (1924) possessed several eggs from the island.
The area covered by breeding birds was accurately determined by using
aerial photographs. The mean density of breeding birds was obtained from
counts of nests within a number of 15 x 15 m quadrats arranged along a transect
throughout the main albatross-penguin colony on the west side of the island.
Other representative quadrats were analysed in the smaller colonies. From these
data, a population of between 140000 and 170000 pairs was calculated in an
area of 23 ha (Prince, 1981). About 102000 (63% of the total population) occur
within a single unbroken colony covering over 14 ha. The mean density of nests
is 0.7 m-*. This is almost certainly one of the two largest known colonies of
black browed albatrosses in the world, the other being on Steeple Jason Island,
off north-west West Falkland Island. The Falkland Islands population, about
R . I. L. SMITH AND P. A. PRINCE
262
Table 9. List of birds recorded on and near Beauchihe Island
Species
Status
Notes
Rockhopper penguin (Eudyptes crysocome)
Gentoo penguin (Pygoscelis papua)
Macaroni penguin (Eudyptes chrysolophus)
Magellanic penguin (Spheniscur magellanicus)
Black browed albatross (Diomedea melanophrys)
King shag (Phalacrocorax albiuenter)
Rock shag (Phalacrocorax magellanicus)
Dominican gull (Lorus dominicanus)
Breeding
Breeding
Breeding
Possibly breeding
Breeding
Breeding
Breeding
Probably breeding
Dolphin gull (Leucophueus scoresbii)
Falkland skua (Catharacta antarctica)
Giant petrel (Macronectes giganteus)
Possibly breeding
Breeding
Variable breeder
Wilson’s storm petrel (Oceanitex oceanicus)
Common diving petrel (Pelecanoides un’natrix)
Fairy prion (Pachyptila turtur)
Breeding
Breeding
Breeding
About 300000 nests
525 nests
16 nests
About 10 birds seen
140000- 170 000 nests
About 2000-3000 nests
c. 25 nests seen
c. 10 adults: 3 immature birds seen on
shoreline
8 birds seen
2 nests, c 20 non-breeding birds
c. 15 nests in 1977, none in 1980; few
dozen birds around coast
Very abundant
Fairly abundant
Abundant at south and southwest end
of island
SEABIRDS
LAND BIRDS
Striated caracara (Phalcobaenus australis)
Tussock bird (Cinclodes antarcticus)
Cobb’s wren (Troglodytes aedon cobbi)
Black chinned siskin (Spinus barlatus)
Sheathbill (Chionis alba)
Speckled teal ( AnosJauirostris)
Breeding
Breeding
Breeding
Probably breeding
Non- breeding
Breeding
? Falkland pipit (Anthus correndera)
Non-breeder
67 nests; total population c. 250 birds
Very numerous
Frequent
16 individuals seen, mostly in pairs
Groups of up to 22 seen
About 8 birds seen, including 2 adults
with young
3 found dead
BIRDS SEEN OFFSHORE AND OVERHEAD ONLY
South American tern (Stma hirundinacea)
Grey backed storm petrel (Carrodia nereis)
Black bellied storm petrel (Fregetta tropica)
Sooty shearwater (PuBnus griseur)
White chinned petrel (Procellaria aequinoctalis)
Grey headed albatross (Diomedea chrysostoma)
Wandering albatross (Diomedea exulans)
Cassin’s falcon (Falco peregrinus cassini)
Non- breeding
Possibly breeding
Possibly breeding
Possibly breeding
Possibly breeding
Non- breeder
Non- breeder
Possibly breeding
American barn swallow (Hirundo rustica)
Vagrant
I seen over island
Several seen a few km offshore
Occasionally seen a few km offshore
Occasionally seen offshore
Occasionally seen offshore
Rarely seen offshore
Rarely seen offshore
1 seen hunting petrels off cliffs at
south-west end of island
1 seen flying over tussock grassland
half of which occurs on Beauchene Island, represents about 70% of the world
black browed albatross population (Croxall, Prince & McInnes, in press).
The nests, some of which are 50cm high and probably very old, are
constructed mainly of mud and guano, with some tussac leaves and seaweed
incorporated. It is not known whether there has been any major long-term
fluctuation in albatross numbers. Certainly there are very few sites into which
they could expand and the high-level stony plateau towards the south end of the
island is the only major area that is largely uncolonized. However, in a small
part of this site there is evidence of a former small colony with the peaty remains
of former small tussac pedestals and albatross nests. The choice of breeding site
is rather unusual, although not atypical of offshore islands in the Falkland
Islands; breeding colonies are more often found amongst short tussock grass on
THE NATURAL HISTORY OF BEAUCHRNE ISLAND
263
Figure 13. Part of the main black browed albatross and rockhopper penguin colony on the west side
of Beauchhe Island.
steep hillsides overlooking the sea. Obviously, the tussac on Beauchene Island is
too tall and impenetrable for albatrosses to establish nest sites and they have
occupied the only other habitat, which is totally unvegetated. Since the main
colony is situated on a very gentle slope, take-off cannot be accomplished by
Figure 14. Small area of mixed seabird colony with breeding black browed albatrosses, rockhopper
penguins (e.g. lower left), mararoni penguins (e.g. lower right and left centre) and king shags. To
south of ‘Blinn’s Bay’.
264
R. I . L. SMITH AND P. A. PRINCE
launching into the updraught during relatively calm weather. Towards the
south end of the colony, the tussac peat is eroded where large numbers of
albatrosses climb to the margin of the grassland, about 5-10 m above the
colony, and launch themselves into the wind from there. Immediately to the
south of the tussock grassland is a wide open strip of compacted guano
traversing the island, devoid of nests but situated between albatross and penguin
colonies. This is a runway used by albatrosses in calm weather. As the prevailing
wind is from the west, the albatrosses generally congregate at the east end of the
runway and run 20-100 m to gain sufficient speed for lift off, but often colliding
with itinerant penguins. The runway has been described in some detail by
Strange (1976a).
Three food samples obtained from adult birds contained the remains of
unidentifiable fish, another consisted entirely of lobster krill (Munidu sp.,
probably Munidu greguria and M . subrugosa: see Matthews, 1932); a fifth sample
contained 12 squid (Loligo sp.-mean weight 21 g, mean mantle length 97 mm).
Prince (198 1) estimated that the Beauchhe Island population consumes about
55000 tonnes of food per annum, much of which is probably taken within a
radius of c. 50 km from the island.
Rockhopper penguins
The second major component of the avifauna is the rockhopper penguin.
These breed throughout all the albatross colonies in the spaces between the nests
of the latter, although there are a very few small areas adjacent to the eroding
peat edge where penguins alone nest. O n the basis of sample counts and
estimates of area covered by breeding birds a breeding population of 300000
pairs was derived. Although this is significantly lower than previous assessments
(e.g. Strange, 1965a) these latter were made without any ground counts and
undoubtedly overestimated breeding densities. I t is unlikely that there has been
any significant change in breeding population over the last 20 years. This is a
very impressive population and is possibly one of the largest individual colonies
in the Falkland Islands, which contain about 50% of the world population.
Both eggs normally hatch but usually only one chick fledges. One nest was seen
with an adult incubating four eggs, presumably as a result of two females.
The penguins come ashore and go to sea at specific sites where broad rock
benches reach the intertidal zone. The perpetual passage of birds over the rock
creates narrow pathways devoid of any seaweed. However, during storms when
these landing areas are pounded by huge breakers the penguins have to time
their landing precisely, but occasionally they are jettisoned from the breaking
crest of a huge wave, up to 10 m high, across as much as 50 m of rocks. In
several places on the west coast, notably at the waist of the island, penguins
swim and preen in pools of brackish stagnant water; this may serve to wash salt
from the plumage or rid them of parasites, particularly ticks, which were seen
around the eyes of several chicks. Where penguins had to climb steep rocky
slopes as, for example, above the fault towards the south end of the island, the
action of their sharp claws over countless centuries has worn deep elongated
grooves in the rock.
Stomach contents were collected from 29 penguins returning from foraging
trips to sea. Analysis of these samples revealed that the composition by weight of
'I'HE NATURAL HISTORY OF BEAUCHBNE ISLAND
265
material unequivocally identifiable to the main prey type was crustaceans 45%
(mainly the euphausiids Euphasia vallentini, E. lucens and Thysanoessa gregaria, the
amphipod Parathemisto gaudichaudii and a few unidentified isopods and
decapods), squid 53% and fish 2%. However, unidentifiable material was
almost certainly mainly derived from fish and it is likely that the three main
prey classes were being taken in approximately equal proportions.
King shags
The third main component of the huge mixed bird colonies is the king shag.
These nest in relatively small aggregations of up to c. 300 nests at the margin of
the albatross and penguin colonies and usually adjacent to the tussac edge.
Strange (1965a) commented that they were commonest on the east coast, but
the present authors found substantial colonies in the west side of the island also.
The total population probably exceeds 2000 pairs. Their nests are created from
a mixture of mud, guano, seaweed, penguin tail feathers and tussock grass
leaves. Some are quite high and resemble albatross nests. They usually lay and
hatch three eggs but it is not certain how many actually fledge; one nest with
four eggs was seen. They appear to feed mainly on lobster krill (Munida spp.).
Large numbers of these regurgitated crustaceans and occasional small fish
occurred around the shags' nests and also on a terrace of eroded peat, used as a
shag roost, above the southwest corner of the main westcoast mixed colony.
The adults cause a considerable amount of destruction to large tussac plants
by going in droves into the marginal grassland, pulling large quantities of live
and dead foliage from the plants and returning to their nests to incorporate the
material. Many plants have been completely defoliated and killed in this way
and it is possible that shags may have been responsible for the apparent retreat
of the tussac margin and the subsequent erosion of the peat that is evident in
several places.
Striated caracaras
This scavenger and predator (Fig. 15A, B) is now comparatively rare in the
Falkland Islands and occurs chiefly on the offshore islands. Small numbers also
breed on some of the more southerly Fuegian islands, notably Diego Ramirez.
The population on Beauchihe Island is possibly the largest in the world with
about 350 birds estimated by Strange (1965a) but a total of about 250 adults
and first-year immature birds was counted by the authors. Sixty-seven nests
were observed but three were inaccessible and, therefore, their contents could
not be checked. Of the 64 examined 35 were empty but with adults in
attendance, two had eggs and 27 had chicks (ten with three chicks, nine with
two chicks and eight with one chick). I. J. Strange (in litt.) noticed that the
number of caracaras was lower in February 1983 than when he visited the
island 20 years earlier. They nest beneath large rock slabs, on rock and peat face
ledges and occasionally on tussac crowns. Most are around the tussock grass
margin but several also occur in the cliffs along the western coastline. Although
usually well dispersed they do occasionally nest close together, e.g. as little as
6 m apart according to Strange (1965a).
266
R. I. L. SMITH AND P. A. PRINCE
Figure 15. Striated caracaras. (A) Pair of adults near nest (note dead eroded tussac pedestal caused
by continual use as perch). (B) Group of immature birds devouring a rockhopper penguin killed a
few minutes earlier by a sea lion.
The caracara’s breeding cycle appears to be synchronized to a large extent
with that of the penguins. Most of their nests are within about 25 m of a major
penguin and albatross colony. Caracara fledgelings are fed almost exclusively on
penguin chicks, supplemented by occasional adult penguins; albatross chicks
appeared to be rarely taken. Occasionally, injured adult penguins are taken and
THE NATURAL HISTORY OF BEAUCHENE ISLAND
26 7
caracaras also scavenge along the shoreline for the remnants of fish and
penguins killed by sea lions. However, a considerable amount of prey is also
taken at night, for during a 2 h spell of mist-netting for small petrels between
23.00 and 01.00 hours, caracaras were caught in the net on several occasions.
They had been swooping on Wilson’s storm petrels, which were caught in
abundance above ‘Blinn’s Bay’, and wings of these, together with those of
common diving petrels and fairy prions, were commonly found near some
caracara nests.
Caracaras are remarkably inquisitive and tame and will land near to and
closely follow a human intruder into their territory. Strange (1976a) described
how, while pausing to write notes, he was encircled by about 40 caracaras. One
of the present authors (R.I.L.S.) experienced the same situation with a group of
34 first-year immature birds at a locality near the shore on the mid-west coast of
the island; the birds came within a few metres and two pecked at his boots. It
was at the same location that a rockhopper penguin was killed by a sea lion (see
above) and a group of about 20 immature caracaras quickly descended on the
corpse, Another aggregation of over 20 immature birds occurred amongst the
seal-eroded tussac at the northwest corner of the island. O n only one occasion
did caracaras show aggression; when R.I.L.S. put a hand forward towards
fledgelings in a nest both parents attacked and one struck his head a severe
blow.
Other birds
A large colony of gentoo penguins occupies a site on the south side of the
‘runway’ on a raised ‘island’ of compact muddy guano overlying stones, up to
35 cm above the surrounding terrain. There were 525 occupied nests in the
rookery (Strange, 1965a, quoted “about 400 birds” and also “400 pairs”); on
12 December 9Oyi of the eggs had hatched. The nests are widely spaced and the
colony is separated from the adjacent rockhopper penguin and albatross colony
by a zone free of any breeding birds. Macaroni penguins are rare but 16 nests
were found amongst the rockhoppers and albatrosses. The greatest
concentration was a group of 1 1 nests within a small area in the midst of the
mixed colony to the south of ‘Blinn’s Bay’. The remaining nests were scattered
throughout the major colonies. In February 1983 I. J. Strange (in litt.) counted
54 nests, so it appears that this population may fluctuate from season to season.
A few Magellan penguins were occasionally seen walking into or out of the
tussock zone near the pool and occasionally elsewhere, but no nest burrows were
located and it is uncertain whether they breed on the island.
The first South Atlantic breeding population of fairy prions (Fig. 16) was
discovered in 1965 by Strange (1968, 1976a). He made this discovery on the
high rock tower (‘The Citadel’) at the south end of the island, where they were
nesting beneath large rock slabs, but in 1969 he found them to be quite
widespread over the island. This was confirmed by the authors in 1980. Many
were mist-netted at night and also observed at night with an image intensifier
on a rock platform on the southwest coast. Various measurements were made
for comparison with the small population recently found on Bird Island, South
Georgia (Prince & Croxall, 1983). The only additional data are for the
Figure 16. Fairy prion and nest (after removal of rock slab) on ‘The Citadel’.
measurements of five eggs. The means were 44.5k0.6 mm (range 44.0 to 45.0)
by 33.0f 1.4 mm (range 31.0 to 34.3). There is certainly a substantial
population on Beauchihe Island, which must amount to several thousand
breeding pairs. The ‘Citadel’ site may be favoured because of the low level of
predation from caracaras compared with sites close to the tussock vegetation; at
the latter, prion wings were frequently found near caracara nests.
In 1977 R.I.L.S. noted a small colony of about 30 giant petrels, some with
chicks and others with empty nests, near the east end of the ‘runway’ adjacent
to the tussac margin. These were probably Mucronectes giganteus since the
northern species ( M . hulli) is not known to breed in the Falkland Islands. No
colony existed in 1980 and only small numbers of definitely identified
M . giganteus were seen overflying the island or in groups of 10-20 offshore,
usually amongst the kelp beds. However, I. J. Strange (in lilt.) noted a single
large chick at this site in February 1983.
Wilson’s storm petrels are very numerous judging by the large numbers seen
flying over the tussock grass at night and caught in a mist net above ‘Blinn’s
Bay’. Common diving petrels were also abundant and nests and eggs of both
were found in the peat beneath tussac plants around the higher part of ‘Blinn’s
Bay’ and elsewhere on the island (notably around the perimeter of ‘The Hole’);
they may also nest along the tussac-covered cliff tops on the east side of the
island. According to Croxall, Prince & McInnes (in press) this storm petrel is a
very local breeding species in the Falkland Islands and nowhere does it appear
to be as abundant as on Beauchihe Island. No other petrels were found
breeding but at least one other species was probably nesting in the precipitous
tussac-clad slope on the north side of ‘Blinn’s Bay’. It was detected by its call at
night, and may have been a sooty shearwater, some of which were seen
occasionally offshore and breed on some tussac-covered islands around the
Falkland Islands (Woods, 1970, 1975; Croxall, Prince & McInnes, in press).
Black-bellied storm petrels, grey-backed storm petrels and white-chinned petrels
‘THE NATURAL HISTORY OF BEAUCHENE ISLAND
269
were observed from a ship a few kilometres from the island, but their presence
on the island was not confirmed.
Of the other birds, the rock shag was the main breeding species, nesting in
small groups on cliff ledges, but it was not abundant. Two pairs of Falkland
Island skuas constructed nest scrapes during the period the authors were on the
island. One pair, on the eroding peat slope towards the southwest end of the
main penguin-albatross colony, laid two eggs but the birds appeared very
unsettled and after a few days the eggs disappeared, presumably predated by
caracaras. The second pair, adjacent to the tussac zone close to the ‘runway’,
did not lay any eggs even though the female sat on the nest for several days. A
group of about 20 skuas was seen on a rock platform above the southeast shore.
That skuas are not more successful predators or scavengers on the island may be
due to competition from the more aggressive caracaras. Several dominican and
dolphin gulls were seen near the shoreline in several places and three young
dominican gulls were observed. A single tern was seen flying high over the
island. A family of two adult and two immature speckled teal inhabited the pool
and a few other adults occurred offshore in the kelp beds below the boulder
beach on the west coast. No Chiloe widgeon, reported by Strange (1965a) as
‘< uncommon: possible breeder”, were seen. Cawkell & Hamilton (1961)
reported that the wandering albatross was “found breeding in small numbers at
Beauchhe Island in January 1959”. However, there is no substantive evidence
of this species breeding on the island (E. M. Cawkell, personal communication)
and there are certainly no typical nesting habitats.
Of the terrestrial avifauna, the most abundant and noisiest is the tussock bird,
which nests beneath rocks close to the tussock margin, or in the tussock grass
pedestals and eroding peat faces. They feed on a variety of arthropods,
especially spiders, small beetles, flies, micro-lepidoptera and probably the larvae
of a noctuid moth, and young camel crickets, terrestrial amphipods and possibly
earthworms, all of which they obtain amongst the tussock skirt and ground
litter. They also take spiders, beetles and micro-lepidoptera beneath stones,
especially on the high windswept ‘Citadel’, and forage amongst seaweed washed
up on the shore. Like the caracaras they are incredibly inquisitive, entering the
hut and tent in pursuit of flies and even alighting on the authors’ boots and
heads. At dawn each morning several of these birds landed on the apex and
sides of the authors’ pyramid tent, to collect spiders and flies attracted to the
orange fabric.
The other major occupant of the tussock grass is the southern house or Cobb’s
wren which surprisingly, Strange (1965a) recorded as “very few birds”. There
is, however, quite a large population concentrated around the margin of the
tussock vegetation. They feed mainly on small arthropods, especially
micro-lepidoptera, flies, immature camel crickets and possibly spiders, psocids
and micro-arthropods. They are often seen foraging along the storm beaches
adjacent to tussac, darting about like mice beneath boulders and also amongst
the tussac pedestals and skirt. The third true land bird of note is the blackchinned siskin of which about 16 individuals were seen in areas of grassland.
Three pairs were frequently observed in the small stand of tussac in the southeast of the island, while about five other pairs were noted between the southern
and northern extremities of the main tussac area. They were generally
inconspicuous but detected by their distinctive song. They appeared to feed
270
R. I. L. SMITH AND P. A. PRINCE
exclusively on grass seeds and were often seen on tussac panicles. Although
breeding could not be confirmed, it seemed likely that a small number nest on
the island.
In the miniature tussock grass on the rock platform in the southeast of the
island R.I.L.S. found three dead pipits, believed to be Falkland pipits, in
positions suggesting they had been sheltering beneath the plants. The only other
land bird seen on the island was the sheathbill. Although not breeding, a group
of 22 was observed on a rock platform on the southwest of the island, and on
another occasion 12 were seen on the southeast coast. They were not
scavenging amongst the penguin and albatross colonies as they do farther south,
again possibly due to predation by caracaras. A Cassin’s falcon was observed
hunting small petrels offshore and retiring to a ledge on the 60 m high cliffs at
the extreme southwest corner of the island, but no nest was noted. One
vagrant, a barn swallow, was seen flying over the tussac-covered ridge above
‘Blinn’s Bay’. Strange (1965a) also reported a barn swallow as well as a turkey
vulture in 1963, and an ‘oyster catcher’ was observed by the naval party in
1962.
INVERTEBRATES
The invertebrate fauna of the Falkland Islands is very poorly known and with
the possible exception of Coleoptera, all groups of insects and most other orders
are greatly under-collected (Robinson, 1984). Strange ( 1965a) referred to a
small collection of invertebrates made in 1964 on Beauchtne Island but these
were never identified and no trace of them can be found. During the present
survey of the island’s biota, one of the authors (R.I.L.S.) made a collection of
terrestrial arthropods and of a few other phyla. These were obtained mainly by
hand sorting in selected habitats but a smaller number of individuals were
subsequently (at South Georgia, but taking care to prevent contamination by
local taxa) obtained by heat extraction from samples of peat and vegetation.
This survey was in no way comprehensive, yet a large number of orders and
taxa were represented (Table lo), some of which are new to science, while
several other as yet unidentified taxa are believed to be previously undescribed.
The collections have been deposited in the British Museum (Natural History).
The list of taxa given in Table 10 records the habitats from which specimens
were collected but, because of the random nature of sampling (e.g. some
habitats were not sampled for certain invertebrate groups), these should not be
considered as the only habitats in which these taxa may occur. The greatest
diversity of fauna occurred in the tussock grass skirt habitat, although the more
terrestrial habitat of tussock litter was also richly populated.
Spiders and beetles were the most abundant of the mesofauna. Of 55
specimens of spiders collected, including 2 1 adults, seven species have been
identified (Usher, 1983a), of which two are genera new to science (Falklandoglenes
and Beauchenia; Usher, 1983b), one is a new species (Emmenomma beauchenicum)
and another a new sub-species (Auximus fuegianus bransjieldi). The two new
genera are of particular biogeographical significance as their subfamily,
Mynogleninae, was previously known only from Central Africa and New
Zealand and its neighbouring sub-Antarctic islands. The largest, Emmenomma
beauchenicum, has a leg span of 2.5-3.0 cm and an overall body length of up to
1.3 cm. Several species were very abundant in the tussock grass skirt (notably
T H E NATURAL HISTORY OF BEAUCHENE ISLAND
27 1
Table 10. List of invertebrate fauna recorded on Beauchine Island
Habitat
ARACHNIDA
Araneae
Dictynidae: Auximus fuegianus bransfieldi* Usher
Dysderidae: Orsolobus sp.
.
.
.
.
Agelenidae: Emmenomma beauchenicuml Usher .
Emmenomma oculatum Simon .
.
Anyphaenidae: Cayenna strigosa Tullgren
.
Lynyphiidae: Beauchenia striata* Usher .
.
Falklandoglenes spinosa* Usher .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Pseudoscorpionidae
Neobisidae: indetermined*
2 . 4 . 10
2. 9. 10
10
2. 4
2
2. 4. 5. 10
2.
2, 5
Acarina
Cryptostigmata
Oppiidae: Oppia crozetetlsis (Richters 1908)
.
.
.
Cloboppia maior Hammer 1962
.
.
.
Oppia/Globoppia sp.
.
.
.
.
.
Podacaridae: Halozetes cf. crozetensis (Richters 1908)
.
Halozetes marinus (Lohmann 1908)
.
.
Podacarus sp.
.
.
.
.
.
.
Oribatellidae: Oribatella palustris Hammer 1962
.
.
Oribatulidae: Eporibatula cf. australis Hammer 1962
.
Cerloubia cf. bicuspidata (Hammer (1958) .
Ceratozetidae: Furcobates hastata (Kramer 1898)
. .
Granizetes curvatus Hammer I96 1
.
.
Porozetes chauinensis (Hammer I96 I )
.
Porozetes po!ygonalis quadrilobatus Wallw . 1966
Prostigmata taxa not determined
Mesostigmata taxa not determined
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3. 5. 9. 10
3. 5. 6
3
3. 6
8. 9
3
3. 4. 5. 6. 9
3
4. 9
3. 5
2. 3. 10
5. 6. 7. 9
3. 9
INSECTA
Coleoptera
Carabidae: Lissopterus quadrinofatus Wat . .
Oopterus soledadinus (Guer.) .
Trechisibius antarcticus (Dej.) .
Hydraenidae: Meropathus sp.*
.
.
Perimylopidae: Darwinella amaroides End .
Darwinella sp.
.
.
Tenebrionidae: Parahelops sp.
.
.
Salpingidae: Poophylax falklandica Champ .
Curculionidae: Arnathynetes sp . A .
.
Amathynetes sp. B .
.
Lathridiidae: Aridius sp .
.
.
.
Cossoninae: unidentified weevil* .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2. 10
2
2
4. 10
2
2
9. 10
2
2
2
2
9
Lepidoptera
Noctuidae: cf. Agrotis sp.
.
.
.
.
Tineidae: Tinea pallescentella Stainton
.
.
Oecophoridae: Borkhausenia folklandensis Bradley
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
21
2
2
Orthoptera
Gryllaerididae: Parudenusjuklandicus Enderlein
.
.
.
.
.
.
.
2
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4
4
4
Hymenoptera
.
Braconidae: Aphidius sp.*
Pteromalidae: Asaphes sp.*
.
Ichneumonidae: Lissonota sp.*
IS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
272
R. I. L. SMITH AND P. A. PRINCE
Table 10. Continued
Psocoptera
Philotarsidae: ?Latrobiella triangula Blanchard
2, 3, 4
Hemiptera
Aphididae: Pmtamyzus faldlandicus Hille Ris Lambers
4
Collembola
Onychiuridae: Tullbergia sp. .
.
.
Hypogastruridae: Xenylla sp. .
. .
Brachystomellidae: cf. Probrachystomclla sp.
Isotomidae: Cryptopygus cf. antarcticus
.
Cryptopygus cf. caecus .
.
Isotoma sp. A
.
.
.
Isotoma sp. B
.
.
.
Isotoma sp. C
.
.
.
Isotoma sp. D
. . .
Entomobryidae: Entomobrya sp.
. .
Willouisia sp.
.
.
Kattiannidae: Xhttiana sp.
.
.
.
2, 5, 6
3, 4, 5, 9
2
2 , 3, 5, 6
3, 5, 6
4, 5, 6
5, 7, 9
2
3
3, 9
4, 10
7
.
.
,
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Diptera
Chironomidae: Bryophaenocladius sp.*
.
.
cf. Cynnidocladius sp.*
. .
Pseudosmittia sp.*
.
.
Mycetophilidae: indetermined*
.
.
.
Dolichopodidae: Sympycnus sp.*
.
.
.
Syrphidae: Carpascalis sp.
.
.
.
.
Ephydridae: Scatella sp.*
.
.
.
.
Muscidae: Apsil sp.*
.
.
.
.
.
Calliphoridae: Calliphora uicina Robineau-Desvoidy
Helcomyzidae: Paractora antarcha’ Thomson ,
Paractora sp. A
,
. .
Paractora sp. B
.
.
.
Paractora sp. C
.
.
.
Sphaeroceridae: Archiborborus cf. albicans Richards
Penola cu&tidis Richards
.
Sciaridae: indetermined*
.
.
.
.
.
.
.
3L, 6 L
4
6L, 7L
4L
2
2, 4
4, 6L, 7
1, 2
2
1, 2
1, 2
1, 2, 4
1, 2
2
2, 4, 5
2
,
.
.
.
.
.
,
.
.
.
.
.
.
.
.
Other invertebrates
CRUSTACEA
Amphipoda Orchestia scutigcrula Dana
2, 3, 4, 5, 6, 10
OLIGOCHAETA
Annelida
Phraecdrilidae: Phraeodrilus niger (Beddard, ( 1894) .
Acanthrodilidae: Microscolcx falklandicus (Beddard 1890)
Enchytraeidae: Enchytraeus sp.
.
. . . .
4
2, 3, 5, 6, 10
mud beneath
stones in seabird
colony
~~
*: Taxa new to the Falkland Islands archipelago. L: Larvae.
Key to habitats:
1: Tussock grass crown (live foliage and inflorescences).
2: Tussock grass skirt (dead attached foliage surrounding side of plant and pedestal).
3: Tussock grass litter (dead detached foliage on ground and top few centimetres of peat below it.
4: Dwarf tussock grass plants on rock platform at southeast of island.
5: Callifriche antarctica and associated tussock grass litter near northeast of island and tussock litter beneath
Apium australe on south side of ‘The Hole’.
6. Liverworts (Lophocolea spp.) and associated tussock grass litter at top of ‘The Hole’.
7: Moss (Bryum pscudofriquctrum) above ‘Blinn’s Bay’.
8: Crustose lichens (mainly Lecanora cf. lauae) on rock at south end of island.
9: Bark of stranded Nofhofagus spp. trunks at tussac margin on southwest of island.
10: Under rock slabs on ‘The Citadel’ at south end of island.
THE NATURAL HISTORY OF BEAUCHENE ISLAND
273
Auximus fuegianus bransjieldi, Emmenomma oculatum, Falklandoglenes spinosa and
Beauchenia striata) and beneath rock slabs on ‘The Citadel’ (especially
A . fuegianus bransjieldi, E . beauchenicum and Orsolobus sp.); in both habitats they
appeared to form an important component of the diet of tussock birds. Egg cases
and webs were also commonly attached to the underside of stones and on dead
tussac leaves.
The beetle fauna is represented by 12 taxa, of which at least three species are
new to science (R. G. Booth, in lilt.). The genus Darwinella is believed to be
endemic to the Falkland Islands, while the genus Poophylax has a circumAntarctic distribution. Of these the black ground beetle Lissopterus quadrinotatus,
dark brown Parahelops sp. and pale orange Darwinella sp. are large, being about
1.5 cm in length. The tenebrionid beetle, Parahelops sp., a n extremely slow moving
species, was the dominant beetle beneath rock slabs, while most taxa inhabited
the tussac skirt and litter with the small Oopterus soledadinus and Trechisibius
antarcticus the most abundant. A small weevil, Falklandius antarcticus, was
extracted from a sample of Callitriche antarctica litter; the species is common in the
Falkland Islands. The grass litter on the ground and forming the outer zone of
the pedestals possessed an abundance of beetle larvae. Unidentified small larvae
of one or more taxa were very common within the base of tussac tillers,
tunnelling chambers along the lower section of the white succulent stems. Of
about 100 tillers examined almost every one had at least two or three such
larvae. However, they did not cause any deleterious effect to the plants, as
commonly happens in tussac stands in some parts of the Falkland Islands
(Gunn, 1974). Of particular interest was the occurrence of a weevil belonging to
the wood-boring sub-family Cossoninae in one of the Nothofagus logs stranded at
the tussac margin. Such weevils are obligate inhabitors of timber and it may be
that antecedents of this small population on Beauchcne Island reached the
island in the tree trunks from Tierra del Fuego or southern Patagonia several
hundred years ago. A casual examination of the shoreline revealed no
Coleop tera.
The third major group of mesofauna are the Diptera of which numerous flies
frequented the tussock grass. Of the 15 taxa collected at least eight are new to
the Falkland Islands; several are brachypterous. The commonest were Apsil sp.
and Penola eudyptidis which, like most of the species, were most abundant in the
tussac skirt, but during periods of sunshine and calm were commonly seen on
the green blades of grass. They also occurred in the exposed rocky habitat on
‘The Citadel’, although they were seldom seen emerging from beneath rock
slabs. O n calm evenings at dusk, large aggregations of Apsil sp. were observed
near the tips of tussac leaves but were seldom seen on the wing. The apterous
P . eudyptidis was previously known only from a single female found on the neck
of a rockhopper penguin on Kidney Island in 1936. Until the present collection it
was the sole example of the genus. The largest fly seen was the blow fly
Calliphoru vicina with a body length of almost 1 cm, but it appeared to be very
rare. Sympycnus sp. was prominent by virtue of its brilliant green body. A
hoverfly, Carposcalis sp., occurred in the tussac skirt and amongst the dwarf
tussac plants. Groups of several species of midge were frequently seen dancing
over short tussac, in the inter-tussock spaces and along the margin of the
vegetated areas; their larvae were common in the tussac litter.
Three species of hymenopteran insects were collected, all from within
274
R.I. L. SMITH AND P.A. PRINCE
miniature tussac on exposed rocks where they appeared to be scarce, although
they were probably overlooked in the taller vegetation; Aphidius sp. appears to
be new to the Falkland Islands. The aphid Pentamyzus falklandicus was also seen
only in the isolated clumps of dwarf rock tussac where it was abundant. It may
have been eaten by wrens, which occasionally visited these plants.
Lepitoptera were a rather unexpected component of the fauna. Two species
of brachypterous micro-lepidoptera were common amongst the tussac skirt,
eroding peat faces and beneath rock slabs on ‘The Citadel’. Borkhausenia
falklandensis has been reported only from the tussac-covered Kidney Island, to
the north of Port Stanley (Bradley, 1965), while Tinea palludescens is new to the
Falkland Islands, although it is a Patagonian species that has been introduced to
both north and south temperate regions (G. S. Robinson, personal
communication). However, the Beauchihe Island specimens are larger and
possibly belong to a separate sub-species. During sunny calm weather these
flightless insects were often seen crawling over rocks, peat and tussac leaves.
Tussock birds preyed on them, particularly in the rock slab habitat. Bradley
(1965) commented that B. falklandensis is the only known species of this genus
which is brachypterous. He noted that the development of the flightless habitat
is a common phenomenon among small species of Lepidoptera inhabiting the
very exposed sub-Antarctic islands of New Zealand, commenting that it may be
due to the wind factor rather than to a genetic tendency towards brachypterism.
Of particular interest was the existence of a relatively large noctuid moth
associated with the tussock skirt. Although no adults were seen, several pupae
and one larva were found. The caterpillar was pale green, about 2.5 cm long
and 8 mm in section. The live specimen was unfortunately lost and, while faecal
pellets obviously from similar larvae were quite common deep in the tussac skirt,
no other examples were located. I. J. Strange (personal communication) has
noticed what are probably the same moth larvae on Kidney Island. A live dark
brown noctuid pupa, about 1.5 cm long, was found in the surface peat just
below loose tussac litter, but it was devoured by a camel cricket which was
placed in the same container. Several pupal cases were found amongst the tussac
skirt; these may have either hatched into the imago or been preyed on by
crickets.
The largest of the mesofauna is the camel cricket (Parudenusfalklandicus). This
species occurs commonly in tussac skirt on the islands around the Falkland
Islands, although a specimen was also found by R.I.L.S. amongst Empetrum
rubrum and Blechnum magellanicum on Tumbledown Mountain to the west of Port
Stanley. Its existence on Beauchhe Island was first noticed when small
immature individuals were attracted to a light in the field hut at night. Adults
and young were then located in relative abundance in the tussock skirt. Mature
females have a body length of 2-2.5 cm with a 1 cm long cercus; their legs are
up to 2.7 cm long and the antennae up to 3 cm long. Males are smaller, with a
body length of 1.5-2cm and shorter antennae. The antennae of immature
crickets were four times the body length (0.5 cm). These crickets are voracious
predators, particularly of beetle larvae. The genus is endemic to the Falkland
Islands.
The smaller mesofauna consist chiefly of mites, springtails and psocids. The
largest and most prominent were the reddish-brown ant-like psocids (possibly
Latrobiella triangula), which were abundant in the tussac litter and also deep in
THE NATURAL HISTORY OF BEAUCHENE lSLAND
2 75
the tussac skirt. Numerous species of mites, some of which were very abundant,
also occupied these habitats. Unfortunately, only the cryptostigmatid taxa could
be tentatively identified, although numerous prostigmatid and mesostigmatid
taxa were also collected. Mites were invariably associated with plant litter or
decaying organic matter ranging from tussac litter, the most favourable habitat
yielding the greatest diversity of species, to algal detritus beneath stones and
rock slabs. While it has not been possible to indicate which are the predominant
species those occurring in the widest range of habitats appear to be Oribatella
palustris, Oppia crozetensis and Porocetes chavinensis, while Haloeetes marinus was
found only on lichen-covered rock and on stranded tree trunks. Springtails were
not particularly numerous although at least 12 taxa were collected, mainly from
amongst tussac litter, skirt and short moss turf. Species of Cryptopygus, Isotoma,
Tullbergia and Xenylla were the most abundant and widely distributed
collembolans. The only taxon collected from under the rock slabs on ‘The
Citadel’ was a species of Willowsia, but other taxa were possibly overlooked
during hand searching. Two specimens of pseudoscorpions were found, one
amongst the tussac litter and the other deep in the tussock skirt.
Other invertebrates
Two groups are important detritovores in the decomposition cycle of the
tussock grass ecosystem. The earthworm Microscolex falklandicum is abundant in
the surface layer of peat beneath the tussock litter in the inter-tussock hollows
and also throughout the tussac pedestals but mainly in the outer zone; during
wet conditions they even ventured into the tussock skirt. These worms are
commonly up to 7cm in length. Occasional small specimens were noticed in
accumulations of organic debris beneath rock slabs on ‘The Citadel’. A very
small annelid worm, Phreodrilus niger, was recorded only in the bases of the
miniature tussock plants. An enchytraeid worm, Enchytraeus sp., occurred in
large aggregations in wet muddy guano beneath stones in the penguin and
albatross colonies. Other examples of small whitish worms were frequent in the
tussock litter and live tiller bases, but were not sampled. A microscopic
examination of bryophytes revealed the presence of nematode worms and
occasional tardigrades, rotifers and protozoans.
The terrestrial amphipod Orckestia scutigerula is exceptionally abundant in the
tussock litter and also in the base of tussac skirt and beneath rock slabs, feeding
on decomposing organic matter. They are widespread from close to the
shoreline to the highest parts of the island and are a major component in the
diet of the tussock birds. Adults are up to 1.5 cm in length and a large
proportion seemed to be gravid females. It is widespread in similar habitats to
over 100 m altitude on other tussock islands in the Falkland Islands (I. J.
Strange, personal communication) and in coastal areas of southern South
America and Tierra del Fuego ( G . Krapp-Schickel, personal communication).
Freshwater invertebrates
The fauna of the freshwater pond was not examined, but no macroscopic life
was observed in the greenish turbid water during a casual search. The only
aquatic invertebrates noted occurred in a brackish pool in a rock basin about
276
R. I . L. SMITH AND P. A. PRINCE
5 m above high water mark and c. 50 m inland on the west coast. The water was
deep pink in colour and contained a very dense concentration of red copepods.
The pink organic debris on the bottom of the pool appeared to be composed
largely of dead copepods, which gave the water its distinctive colour. A similar
pool was noted amongst rocks southwest of the waist of the island, but all other
such brackish pools were either clear water or green with unicellular algae.
Marine molluscs
No collection of marine invertebrates was made in the intertidal zone. The
most prominent molluscs were limpets, while brilliant red sea anemones were
common in rock pools and on sublittoral rocks. However, there were deposits of
shells and shell sand in an area on the rock platform towards the southeast of
‘The Arena’, about 20-25 m altitude and up to 100 m inland from the east coast.
The material had been lifted from the inshore sea bed during storms and
transported inland by exceptionally large waves. Amongst these deposits were
many entire or nearly entire, although rather worn, shells for some of which
identifications were possible (Table 11). All are known from the Falkland
Islands coasts and have a Magellanic rather than Antarctic affinity, and most
are of shallow water taxa. Fragments of sea urchin tests were also present
amongst this material.
Table 11. List of marine molluscs recorded washed ashore on BeauchCne Island
Aulacomya oter (Molina 1782)
Balboaina picta (Cmelin 1791)
Certhium cf. pullum (Philippi 1845)
Crepipatella dilatata (Larmarck 1822)
Caimordia lrapesina (Lamarck 1819)
Kerguelenella lateralis (Gould 1846)
Limatula pygmaca (Philippi 1845)
Lissarca miliaris (Philippi 1845)
Mytilus edulis chilensis (Hupt 1854)
Nacella mytilina (Helbling 1779)
Pareuthria cf. magellanica (Philippi 1845)
Photinustomu tacniatus (Wood 1828)
C;lypteuthria sp
Philobrya sp.
Xymenopsis sp.
DISCUSSION
The Beauchtne Island survey has provided a preliminary inventory of the
major floristic and faunistic groups and, while in no way comprehensive, the
identification of numerous terrestrial arthropod taxa has added significantly to
the otherwise poorly known invertebrate fauna of the Fplkland Islands. The
breeding status of the avifauna has been assessed and the population size of the
principal species determined reasonably accurately, reducing previous estimates
for breeding numbers of black browed albatrosses and rockhopper penguins
about ten-fold. None the less, with the possible exception of some of the Midway
Islands in the Hawaiian archipelago, Beauchhe Island supports what is
probably the largest population of albatrosses in the world, and almost certainly
the largest single colony (c. 102 000 pairs). It also possesses one of the two largest
penguin colonies in the Falkland Island. These birds, together with substantial
populations of other seabirds, including king shags, fairy prions and Wilson’s
THE NATURAL HISTORY OF BEAUCHENE ISLAND
277
storm petrels, must have a significant impact on the marine resources of the
surrounding ocean. The island may also hold the largest population of striated
caracaras, a species which Strange (1976a) regarded as a strong candidate for
inclusion on the world list of endangered species. The island is important as the
stronghold of the South Atlantic population of fairy prions and also one of the
most northerly major breeding sites of Wilson’s storm petrel’s.
The island is not an important site for sea lions and is no longer a breeding
site for fur seals. However, there was unquestionably a major fur seal colony
there during the late eighteenth and early nineteenth centuries, before sealing
activities reduced numbers to a handful at the beginning of the twentieth
century, with the last reported animals killed there in 1919. There is a history of
fur seals (and sea lions also) on the island dating back over 11 000 years, as
revealed by the occurrence of hairs belonging to these animals, preserved
throughout the deep deposits of tussac peat. These hairs increase considerably in
abundance in the peat from around 4000 years B.P. to the present.
It is interesting to speculate about the development and subsequent erosion of
these peat deposits. Certainly the abrupt margin of deep peat, in places actively
eroding but elsewhere protected by slumped live tussac plants, along the west
and southeast side of the island gives the impression of a once much more
extensive cover of tussock grass, especially towards the western shore. An almost
identical situation has been reported from sub-Antarctic Marion Island in the
Indian Ocean (Hall & Williams, 1981) where two exceptionally large and dense
colonies of macaroni penguins are responsible for the destruction of the surface
vegetation and up to 4 m of peat. According to the radiocarbon date for organic
material at the base of an eroding peat face on Beauchihe Island, plant
colonization commenced about 12500 years ago. Prior to that it may have
supported a more open fellfield type of vegetation that does not accumulate peat,
during an era with a cooler drier climate, i.e. during the Pleistocene when the
Falkland Islands were extensively covered by ice caps. Since the establishment
of tussock grass, which favours cool moist conditions, there is no evidence of any
other major vegetation type developing on the island. However, a period of
wetter conditions about 8000-7000 years ago may have been responsible for
changing the nature of the peat, which was subsequently compressed into
material resembling lignite. The tussac cover may have extended over most of
the northern two-thirds of the island; then, perhaps about 4000 years ago, it
became increasingly colonized by fur seals which, as their numbers increased,
gradually killed much of the more accessible grass, leading to surface erosion.
This has also been happening at localities at South Georgia (e.g. Bird Island,
Elsehul) during the past two decades.
It is suggested that during the past several millenia the grass and peat have
been removed by biotic erosion to near their present boundary but, at some
stage in the disappearance of the exceptionally tall grass, perhaps coinciding
with a southward migration of the Antarctic Convergence to near its present
position, the grass-free area became colonized by penguins and albatrosses (but
see below). Such colonies may have already existed for a long time on the
unvegetated rocky southern part of the island (a few barbs of feathers were also
detected microscopically in deep peat samples). However, certain changes in the
status of the seal and bird populations may be quite recent. While Morrell
(1832: 54) referred to the island as barren but with fur seals and many kinds of
278
R. I. L. SMITH AND P. A. PRINCE
seabirds, Fanning’s (1834) illustration of fur seals at Whirlwind Point is of
particular interest. The seals are clearly depicted but no birds are shown; today
there are no seals there but the entire tussac-free area is occupied by a dense
mixed black-browed albatross (c. 8000 nests) and rockhopper penguin colony,
suggesting a dramatic change during the past 150 years since the disappearance
of the seals. Could much of the rest of the massive albatross and penguin
population along the west coast have developed during this period also, as
competition for breeding space and food was rapidly removed? With regard to
the removal of tussac and the subsequent erosion of the underlying peat it is
therefore suggested that this had been achieved by fur seals rather than by the
penguins and albatrosses, the former of which seldom nest amongst dense
tussock grass and the latter often nesting in short tussac but typically on steep
slopes. It is possible that the erosion of vegetation and peat at the macaroni
penguin colonies on Marion Island were also caused by fur seals prior to their
slaughter, since macaronis typically breed on barren rocky slopes.
There is little evidence of albatrosses or penguins causing serious damage to
tussac plants, although the former do pull out live leaves and tillers along the
periphery of the grassland adjacent to the colonies, for nesting material.
However, in places they enhance erosion of bare peat cliffs and slopes by
climbing to the exposed crest from where they take off. A similar effect is caused
by large numbers of immature rockhopper penguins which climb the peat face
to moult amongst the tussac above it. Currently on Beauchihe Island, perhaps
the most significant agent of erosion is, surprisingly, king shags, which are
devastating small marginal areas of tussac by stripping them of dead and live
foliage to use as nesting material (Fig. 17). Sea lions, particularly in the northwest corner of the island also appear to be causing localized erosion.
Undoubtedly wind action is eroding areas of peat cliff, especially the exposed
Figure 17. Damage to marginal tussock grassland and erosion of peat caused by king shags
removing live and dead foliage for nest material.
THE NATURAL HISTORY OF BEAUCHENE ISLAND
279
crest. Here, the outermost tussac plants along stretches of the windward edge
are distinctly wind damaged. As erosion proceeds, the surface crumbles and
accumulates as a ramp below the cliff, this action being further enhanced by
heavy rain.
The tussock grass ecosystem represents a remarkable environment and biota
for the study of terrestrial trophodynamics and biological processes. The
luxurience of the plants is due largely to the aerosol of nitrogenous products
drifting to the leeward of the vast penguin and albatross colony. Each tussac
plant is an independently functioning clone of units (tillers) in a monospecific
‘forest’. The most diverse component of this system is that of the invertebrate
(predominantly arthropod) fauna, and the interrelationships between
detritivores, herbivores and carnivores is relatively complex and to some extent
stratified according to the various niches associated with each tussac plant. The
macrofaunal component is represented by few species, mainly tussock birds and
wrens and the seed-eating siskins but these occur principally around the margin
of the tussac vegetation. Burrowing petrels (Wilson’s storm petrels, diving
petrels and possibly shearwaters) living beneath the tussac plants are important
mainly in their action of aerating the root systems of the vegetation, but their
colonies are fairly localized around the periphery of the grassland. They are
predated by striated caracaras. A major reason for the abundance and success of
the two passerines and the burrowing petrels must be the absence of rats or
other alien predators which have had such a serious influence on many islands
of the Falklands archipelago. Woods (1970) gave a detailed account of the
distribution of the avifauna in such tussac vegetation on Kidney Island and,
both he and Strange (1976b), have illustrated the relationship between nesting
sites of the various species and their position in an individual tussac plant. However, these examples were considerably more complex than the situation
on Beauchhe Island which, therefore, offers a fascinating simple ecosystem
in which ecological hypotheses, particularly related to predator-prey
interrelationships, may be tested. An attempt to depict the distribution of
breeding birds and the major invertebrate groups in a typical BeauchZne Island
tussac plant is shown in Fig. 18.
The peat deposits of Beauchtne Island may also be of considerable interest
and value in the study of the coalification of plant matter since the transition to
a form of lignite has taken only a fraction of the time scale normally associated
with the process. The island’s deep relatively dry peat may also be a valuable
source of palynological information since the native vascular flora appears to
have been virtually monospecific, perhaps for as long as 13 millenia. Thus the
non-graminaceous sporomorpha content of the peat should represent exotic taxa
and fluctuations in their abundance through the profile may give a good
indication of floristic and hence climatic change in the Magellanic region
(Patagonia, Tierra del Fuego, Falkland Islands) as a whole. Fluctuations in the
density of arthropod remains may also reflect climatic change.
Beauchkne Island has been a seal reserve under the Seal Fishery Ordinance
for over 60 years, and on 30 December 1964 an order was issued under the Wild
Animals and Birds Protection Ordinance 1964 declaring the island to be a wild
animal and bird sanctuary. With increasing tourist interest and activity in the
Falkland Islands and the threat of mass landings on Beauchtne Island and likely
disturbance of the avifauna (see Strange, 1976a) (and even the possible threat of
_
280
_
R. I. L. SMITH AND P. A. PRINCE
~
Pseudoscorpions
Spr inqtaiIs
Amphipods
Im
Mites
Sprinqtoils
Earthworms
Nematodes
fire devastating the tussac grassland and peat during dry weather), a major
attempt to protect the island’s biota has been made by the government adviser
on wildlife and conservation matters, I. J. Strange. As neither the Seal Fisheries
Ordinance nor the Wild Animals and Birds Protection Ordinance give adequate
protection to wildlife, improved conservation measures are being drawn up to
provide better legislation in the future. Since the Falkland Islands conflict of
April-June 1982 much more interest is being shown in conservation of
biologically important sites in the islands (Strange, 1983). Fortunately, the
conflict did not impinge upon the BeauchCne Island environment; recent visits
by the military and government conservation advisers have confirmed that the
wildlife has not been disturbed in any way (Sir Rex Hunt, personal
communication). BeauchCne Island occupies a key strategic position in the
geography of the Falkland Islands, if an economic exclusion zone is ever
established around the archipelago, since it would extend the limit well to the
south. Furthermore, because the Falkland Islands have only a three-mile ( 5 km)
territorial limit, there is a new potential threat to the black browed albatross
population of BeauchCne Island since foreign fishing fleets are taking huge
catches of squid within the foraging range of these birds. It is hoped that
Beauchtne Island will be recognized as a unique site of major biological interest
where access will be strictly controlled and no disturbance of the environment or
THE NATURAL HISTORY O F BEAUCHENE ISLAND
28 1
biota will be permitted. The Foreign and Commonwealth Office, London, has
given its assurance that both the civil and military authorities in the Falkland
Islands are aware of the need to ensure the future conservation and protection of
the area as a whole and of Beauch2ne Island in particular.
ACKNOWLEDGEMENTS
A great many people have made this account possible and to each we express
our sincere thanks. First, we are indebted to Captain S. Lawrence and the
officers of the R.R.S. Bransjield for efficiently effecting our safe landing on and
recovery from Beauchhe Island. The following specialists were responsible for
providing data or determinations reported in this survey:
Vegetation: Dr C. M. Matteri (mosses) and Dr G. G. Hassel de Menendez
(liverworts), both of Museo Argentino Ciencias Naturales Bernardino
Rivadavia, Buenos Aires, Argentina; Dr D. 0. Bvstedal, University of Tromsra,
Norway (lichens); Dr D. M. Pegler and B. M. Spooner, Royal Botanic Gardens,
Kew (fungi); Dr J. Priddle (algae) and Dr D. D. Wynn-Williams (bacteria and
yeasts), both British Antarctic Survey; Dr L. Donaldson, Forest Research
Institute, Rotorua, New Zealand (stranded trees).
Peat: Dr F. J. Rich, School of Mines and Technology, South Dakota, U.S.A.,
and Dr J. D. Yeakel, J. C. DeVine, J. B. Bodkin and H. Gong, College of Earch
and Mineral Sciences, Pennsylvania State University, U.S.A. (analysis of lignitic
peat); Dr D. D. Hardness, NERC Radiocarbon Laboratories, University of
Strathclyde, Glasgow (radiocarbon dating); Dr J. D. Roberts, Institute of
Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands
(chemical analyses); D. W. Doidge, British Antarctic Survey (sub-fossil seal
hairs).
Minerals: Dr J. Esson, Department of Geology, University of Manchester.
Birds: Dr J. P. Croxall, B. C. Osborne, P. Ward and Mrs A. McCann (food
analyses).
Invertebrates: Dr M. B. Usher, University of York (Araneae); Dr J. A.
Wallwork, Westfield College, University of London (Acarina); P. D. Hillyard
(Pseudoscorpionidae), Dr G. S. Robinson (Lepidoptera); Dr R. G. Booth,
University of York and R. D. Pope, British Museum (Natural History)
(Coleoptera); Mrs J. A. Marshall (Orthoptera), T . Huddleston, Dr J. S. Noyes
and I. Gauld (Hymenoptera), R. L. Blackman (Hemiptera), Dr P. N.
Lawrence (Collembola), B. H. Cogan, P. S. Cranston, C. E. Dyte, B. R. Pitkin,
A. C. Pont, K. G. V. Smith and N. P. Wyatt (Diptera), Dr R. W. Sims
(Annelida), all British Museum (Natural History); Dr G. Krapp-Schickel,
Adendorf, Bonn, West Germany (Amphipoda); Dr P. G. Oliver, National
Museum of Wales, Cardiff (marine molluscs).
Finally, we wish to express thanks to Dr R. M. Laws, Director, British
Antarctic Survey, who gave his consent for us to undertake this work, and to Sir
Rex Hunt, Civil Commissioner (then Governor) of the Falkland Islands, for
permission to make a prolonged visit to the nature reserve of Beauchihe Island.
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