AMER. Zooi..,
14:185-204
(1974).
Ecology and Evolution of Social Organization
in Arctic Sandpipers
FRANK A. PITELKA
Museum of Vertebrate Zoology, University of California,
Berkeley, California 94720
RICHARD T. HOLMES
Department of Biological Sciences, Dartmouth
Hanover, New Hampshire 03755
College,
AND
STEPHEN F. MACLEAN, JR.
Department of Biology, University of Alaska, Fairbanks, Alaska 99701
SYNOPSIS. A comparative analysis of sandpiper social systems on arctic and subarctic
breeding grounds (24 species in the family Scolopacidae, subfamily Calidridinae) shows
four major patterns. In a majority of the species (15), populations are dispersed through
a strongly developed territorial system, with strong monogamous pair bonds and only
minor yearly fluctuations in numbers. The second pattern is seen in three species in
which the female of a pair may lay two sets of eggs in quick succession, one for each
member of the pair to incubate. This opens opportunities for facultative polygyny or
polyandry ('serial polygamy') and for the evolutionary weakening of the strong pair
bond seen in the first pattern. The third and fourth patterns are those of polygyny
(three species) and promiscuity (three species). These six species show clumped dispersions; their year-to-year fluctuations tend to be strong; the males defend compressible,
often small, territories; and high densities can occur locally. It is suggested that the
pattern of overdispersion and monogamy represents a conservative mode of adapting
to high-latitude environments, while the pattern of clumped dispersion with polygyny
or promiscuity represents an opportunistic mode in that the birds are concentrated into
breeding areas where and when weather, food, and/or some other environmental factors
are particularly favorable. Apparently falling evolutionarily between these two basic
patterns are several species conservative in their life-styles, but polygamous at least
occasionally and showing some features of opportunism. There is thus a striking diversity of social systems in calidridine sandpipers, that is, in the styles of habitat exploitation they have evolved in the arctic and subarctic habitats to which their breeding is
confined. A graphic model suggesting paths of evolutionary development and of interplay among factors considered critical in the evolution of these systems is proposed.
Our work with shorebirds in northern Alaska has
been supported by grants to F. A. Pitelka from the
Arctic Institute of North America under contractual
arrangement with the Office of Naval Research.
Field support was provided by the Naval Arctic
Research Laboratory at Barrow. Since 1969, additional observations on northern Alaskan shorebirds
have been made incidental to other field work under the U.S. International Biological Program for
Tundra, supported by the National Science Foundation. Background work for this paper was done
by Pitelka during the tenure of a fellowship at the
Center for Advanced Study in the Behavioral Sciences (Stanford, California) in 1971.
Over the past 10 years we have profited from
numerous discussions in seminars and professional
meetings where successive versions of this work have
been presented. During summers at the Naval Arctic Research Laboratory, day-to-day, "on-location"
discussions with colleagues have been especially useful and stimulating, and while it is impossible to
name them all, we express our thanks particularly
to T. W. Custer, D. W. Norton, J. V. Remsen, U. N.
Safriel, M. Soikkeli, and N. A. M. Verbeek. For
information not yet published, we express warm
thanks to J. R. Jehl, Jr., A. A. Kistchinski, E.
Ostbye, L. W. Oring, D. F. Parmalee, R. B. Payne,
and R. L. Zusi. For access to a Russian translation,
we are indebted to R. S. Palmer.
185
186
PITELKA, HOLMES, AND MACLEAN
INTRODUCTION
A species' strategies in exploiting its
environment successfully are ultimately
integrated into that collection of adaptations comprising its social system. This set
of adaptations is to be seen in the pattern
of social interactions among members of
a population in relation to spatial and
temporal characteristics of its environment.
The basic interactions are those of distribution of individuals in the habitat (dispersion), the relations of the sexes in breeding (mating system), and the pattern of
parental care. Correlated with the social
system are such features as degrees of
sexual and age dimorphism, age at reproductive maturity, and the particular form
of display behavior related to reproduction. All of these and other characteristics
combine as a syndrome to influence success
in location and use of environmental resources and, therefore, success in breeding.
More specifically, then, "social system" or
"exploitation system" can be denned as
that pattern of deployment and activities
of members of a population in space and
time adaptively serving needs of self-maintenance and successful reproduction in relation to a given environment. It is our
objective to examine patterns of social
organization from this point of view for a
major group of birds, a subfamily of sandpipers breeding on arctic and subarctic
tundra, and to propose a model to account
for the evolutionary divergence of social
systems among members of this group.
Only recently have investigators considered the adaptive significance and evolution of the diverse patterns of social
organization found in animal populations
(e.g., Crook, 1965, 1970; Selander, 1965,
1972; Lack, 1968). Orians (1969), Bartholomew (1970), and Downhower and Armitage
(1971) have proposed models to account
for the evolution of polygyny in particular
groups of birds and mammals. An approach which has, thus far, proved especially useful involves (i) comparative analysis of the patterns found among related
species, and (ii) correlation of particular
features of social systems with the environ-
ments in which they occur (Orians, 1961;
Crook, 1965; Verner and Willson, 1966;
von Haartman, 1969). To make such correlations and interpretations, detailed ecological and behavioral studies of animal
populations in their typical environments
are needed so that specific patterns of social
behavior can be placed into their ecological context and so that hypotheses regarding their evolutionary development
can be formulated.
Our analysis of the array of social systems in sandpipers is based largely on
results of long-term studies in northern
and western Alaska (Pitelka, 1959, 1969;
Holmes, 1966a,6,c, 1970, 1971a,&, 1972,
1973; Holmes and Pitelka, 1964, 1968; MacLean, 1969; MacLean and Holmes, 1971),
supplemented by other published accounts.
Our field work with the group includes
direct experience with 15 of the 24 species
on their breeding grounds. Information on
some species, particularly those breeding
on Siberian tundra, is far from complete.
Nonetheless, we feel that the available
data reveal enough of the general patterns
of sandpiper social organization to enable
us to postulate the main features of their
evolutionary development. The conclusions reached in this discussion are not
intended to be definitive, but should be
taken as hypotheses to be evaluated and
modified, extended, or rejected as additional information becomes available.
THE SANDPIPERS AND THEIR SOCIAL SYSTEMS
General characteristics and taxonomy
The sandpipers considered in this paper
are shorebirds of the family Scolopacidae,
subfamily Calidridinae. These birds breed
exclusively on arctic or subarctic tundra,
meadows, or bogs. They are relatively small
birds, ranging in weight from 17 g (Calidris
minutilla) to 170 g (male Philomachus
pugnax).
The subfamily Calidridinae includes 24
species, 18 of which are placed in the inclusive genus Calidris (B. O. U., 1952; Kozlova, 1962; Holmes and Pitelka, 1964). The
other six species represent monotypic
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
genera, each of which possesses rather distinctive morphological characteristics. We
agree with Peters (1934), Kozlova (1962),
and Jehl (1968) in excluding the genera
Limosa and Limnodromus. We do include
as a calidridine, however, the surfbird
(Aphriza virgata), based on plumage characteristics of its downy young (Jehl, 1968),
anatomy (R. L. Zusi, personal communication), and breeding behavior (MacLean,
unpublished).
Sandpiper social systems
Four major types of social systems are
found among the 24 calidridine species
(Table 1, see appendix). Each can be distinguished by a variety of features, but is
most simply characterized by type of mating system. Consequently, we refer to the
categories here as (I) monogamous, (II)
serially polygamous, (III) polygynous, and
(IV) promiscuous.
Group I: The monogamous species. Based
on present information, 15 of the 24 calidridine species appear to possess social systems in which monogamous breeding pairs
are dispersed evenly over suitable habitat
by territorial systems. The densities of each
species in a particular geographical locality
remain relatively stable from year to year
(Table 1).
Pair relationship: In these species a pairbond is formed between a male and a female, which lasts through the incubation
period and, in some cases, until the young
are fledged. Both sexes participate in incubation at a single nest. In some species
renesting may occur upon loss of the first
nest.
The most common display associated
with pair formation in calidridine sandpipers is nest-scraping (Holmes and Pitelka,
1964; Parmelee, 1970; Holmes, 1973). This
activity has been reported in 8 of the 15
monogamous species (Table 1) and may
well be found in others of this group when
they receive intensive study. This type of
display is also found in other species that
form pairbonds (Group III and at least
one species of Group II), but it is absent
from the display repertoires of the pro-
187
miscuous species (Group IV).
There is only slight sexual dimorphism
in the monogamous species. In every case,
females are larger than males (Table 2,
see appendix). No significant color differences are found between sexes, and none
of these species has conspicuous secondary
sexual characters.
Dispersion patterns: Spacing within populations of the monogamous species is
achieved by well-developed territorial behavior. The males actively defend and
advertize their territories by flight displays
in which they hover at varying heights
above the ground, often for several minutes
at a time, and give trilled or whistled songs.
Our studies of C. alpina, C. bairdii, and
C. pusilla in northern Alaska, and C. alpina and C. mauri in western Alaska indicate that within a geographic region, density and territory size are relatively stable.
No reports were found in the literature of
large fluctuations in densities of other
members of this group. Such records do
exist for several of the polygynous and
promiscuous species considered below.
Therefore, it seems that most if not all
species in this group are dispersed relatively evenly over the available habitat
each year. Some occur consistently at relatively low densities (e.g., C. alpina in northern Alaska and C. canutus), but others
occur regularly at high densities (e.g., C.
mauri in western Alaska and C. pusilla in
northern Alaska). The high densities reflect
extremely favorable environments. In C.
mauri, for example, a restricted but highly
favored nesting habitat is surrounded by
good foraging sites, and feeding often occurs off territory on communal feeding
areas (Holmes, 19716). In species occurring
in relatively low densities (for example, C.
alpina in northern Alaska), the pair obtains most or all of its food on a large territory.
Group II: The serially polygamous species. In two, and perhaps three, calidridine
species, females lay two successive clutches,
each of which is incubated by a single
adult. This has been documented by Hilden (1965) for C. temminckii and by Parmelee (1970; Parmelee and Payne, 1973)
188
PITELKA, HOLMES, AND MACLEAN
for C. alba. For the former species, both
Hilden (1965) and Ostbye (personal communication) report that the number of
nests on their study areas was equal to the
total adult population. Thus, each adult
bird was involved in, on the average,
two nests. Kistchinski and Flint (1973),
in a recent study in north-central Siberia, found only two nests of C. minula
in a 15-km2 study area. They were located
about 6 m apart, one incubated by a male,
the other by a female. If these were the
two members of a pair, each with its own
nest, then a situation similar to that described for C. temminckii and C. alba exists in C. minnta. This interpretation may
help to clarify the confusion in the literature concerning the role of the sexes in
incubation in C. minula. Grote (1937),
summarizing the Eurasian literature, found
that both sexes had been collected from
nests, while others have reported that incubation is only by the female (Rutilevskii,
1963) or only by the male (references cited
in Dement'ev et al., 1951).
Pair relationship: These reports suggest
two interpretations of the pair relationship: (i) a persistent pairbond is formed
between a male and a female; the female
lays two clutches, the first being incubated
by the male and the second by the female;
(ii) a female may form a series of temporary pairbonds with different males, laying
a clutch which is incubated by the first
male, and, after association with another
male, a clutch which the female or both
sexes incubate. Hilden (1965) found a female C. temminckii associating, serially,
with two different males. Parmelee and
Payne (1973) found evidence that a female
C. alba which had laid two clutches had
additional large yolky follicles suggesting
she might have laid a third. If all three
were to be incubated, they would require
the participation of at least two males.
Both Hilden (1965) and Parmelee and
Payne (1973) found that males did not
commence incubation immediately; instead, there was a delay (4 to 5 clays in
C. alba) during which the male was not
observed and the nest was unattended. During this absence, they suggest, the male
may be competing with other males for
the attention of his first mate (for her
second clutch) or for another female.
Thus, the mating system may contain
elements of both polyandry and polygyny
and is best described by the broader term
polygamy, and more specifically as serial
polygamy, since the interactions between
the sexes apparently occur successively or
serially. When more information is available, this type of mating pattern may prove
to be very similar to that found in the
Spotted Sandpiper (Actitis macularia, a
member of the scolopacine subfamily Tringinae) by Hays (1973) and by Oring and
Knudson (1973). The latter authors refer
to this condition as serial polyandry.
The occurrrence of multiple clutches in
Group II and the incubation of each by a
single adult are significant departures from
the mating pattern of Group I species. The
fact that males incubate separates Group
II species from those of Group III and IV.
An interesting possibility suggested by
Group II species is that if only some females in a population produce second
clutches, and depending on the time-span
of this capacity, opportunities for multiple
copulations by males might lead to their
abandonment of incubation and thus to
polygyny as seen in Group III.
Dispersion patterns: Little information
is available on the spacing characteristics
of these three species. Southern and Lewis
(1938) and Hilden (1965) indicate that
male C. temminckii occupy small territories and that densities can be quite high
in local areas. Parmelee (1970) reports that
densities of C. alba in the Canadian arctic
archipelago are low and variable, ranging
from less than one to three males per
square kilometer. Kistchinski and Flint's
(1973) report of C. minuta indicates a very
low breeding density; however, Dement'ev
et al. (1951) report this species to be ". . .
almost the most numerous shorebird" on
the Kanin Peninsula in western Siberia.
Present knowledge of this interesting
system is far from complete, and our inclusion of C. minuta in this group is admittedly tentative. More detailed studies
of the breeding system ecology and be-
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
havior of these three species are urgently
needed.
Group III: The polygynous species. Two
species (C. fuscicollis, C. ferruginea) and
possibly a third (C. acuminata) possess
breeding systems in which the males maintain simultaneous pairbonds with more
than one female. Population densities vary
markedly between years and between local
regions within a season.
Pair relationship: In all three species,
males take no part in incubation; they do
not develop brood patches and do not take
care of the young. In C. fuscicollis (Holmes
and Pitelka, unpublished) and C. ferruginea (Holmes and Pitelka, 1964; Pitelka
and Remsen, unpublished), some males
maintain pairbonds with two or three females. The males perform frequent and
elaborate nest scraping displays, and females nest on the male's territory. Parmelee et al. (1968) cited the close proximity
of two nests of C. fuscicollis as evidence
that females ". . . nested without regard
to the male's territory"; however, they were
not aware of the polygynous breeding system, and more likely, the two females had
mated with a single male.
Calidris
fuscicollis
and
C.
ferruginea
have essentially no sexual dimorphism in
size (Table 2). Males of C. ferruginea are
noticeably brighter in color than females
(Holmes and Pitelka, 1964). Thus, these
species deviate from the female-larger,
monomorphic-plumage pattern found consistently in the monogamous sandpiper
species.
Dispersion patterns: The spacing patterns and densities of the Group III species
appear to be variable both in time and
space. At a given locality they may be very
common one year and scarce or absent the
next (Holmes and Pitelka, 1964, unpublished; Parmelee et al., 1968). Even in seasons when they are relatively common,
their distribution on the tundra is clumped.
The variation in density of C. fuscicollis
is reflected in display behavior. In dense
populations the territorial display of males
is a low flight, with a sudden rise to a
height of 5 to 10 m, a song, and then a
glide back to the ground on outstretched
189
wings. At low densities, the males rise to
heights of 15 or 30 m and give a repeated,
trilled vocalization during long hovering
flights (Holmes and Pitelka, MS).
The only evidence on dispersion patterns in C. ferruginea comes from two
groups of birds that bred near Barrow in
1962 (Holmes and Pitelka, 1964) and in
1972 (Pitelka and Remsen, unpublished).
We cannot be certain that these groups
exhibited the breeding dispersion characteristic of this species on its Siberian breeding range. In both years at Barrow, however,
the birds were not dispersed evenly over the
tundra, but were associated closely with
several males occupying adjacent territories. In the sparser population of 1962,
members of courting pairs remained mobile, and the focus of courting and territorial activity shifted from day to day, but
in the denser population of 1972, attachment to territory in the main cluster of
breeding birds was as strong as in species
of Group I. In territorial advertizement, a
male C. ferruginea displays close to or on
the ground and gives a relatively weak,
complex song of trilled phrases ended with
a whistled note. This display form and
song type are suggestive of clumped or
normally dense local populations, and the
former closely resembles the display style
of male C. fuscicollis in high-density populations.
We include C. acuminata in this group
mainly on the report of Vorobiev (1963)
that only females incubate and that males
do not develop brood patches. These characteristics separate it from species in
Groups I and II but do not rule out the
possibility that it is promiscuous and, thus,
belongs in Group IV. Calidris acuminata
shows more sexual dimorphism in size than
C. fuscicollis and C. ferruginea, but it is
less dimorphic than any of the three species
of Group IV (Table 2).
The breeding biology of C. acuminata
was recently observed by Kistchinski (personal communication). He reports that they
are generally clumped in distribution on
Siberian tundra, but they show less spatial
variation than C. melanotos (of Group IV,
discussed below). On two study areas C.
190
PITELKA, HOLMES, AND MACLEAN
acuminata occurred at densities of 10 to 15
males/km2, while 1 to 2 male C. melanotos
occurred per square kilometer on one area
and 20 to 25 males/km2 on the other. The
display form also suggests that they typically occur at intermediate densities; in
display flight, they rise to heights of 30 to
50 m, much higher than C. melanotos, but
lack the continuous vocalization given in
hovering flight by males of more dispersed
species, including C. fuscicollis at low densities.
Group IV: The promiscuous species.
Three calidridine species, Calidris melanotos, Tryngites subruficollis, and Philomachus pugnax, have promiscuous mating
systems. Their spacing patterns can be
characterized as clumped territories of
variable size, an "exploded lek," and a lek,
respectively.
Pair relationship: In all three species
males take no part in incubation and show
no interest in the nest. They characteristically leave the breeding area before
the young have hatched. No persistent
pairbonds exist; females may be seen associating with a number of males in close
succession, and a male actively displays
toward any female that enters his territory.
In T. subruficollis and P. pugnax, and occasionally in C. melanotos, the females nest
away from the territories of the males,
visiting the display grounds only for copulation. Thus, mate selection is exercised
by the female and the possibility exists
that a different choice is made with each
visit to the displaying males. The nestscraping display used by males of the other
groups in establishing pairbonds is not
seen in these species.
As might be expected in a system in
which females choose males in this way,
there is an increase in sexual dimorphism
(Table 2). This is most pronounced in C.
melanotos and P. pugnax, in which the
males are much larger than females and
possess conspicuous secondary sex characteristics, an inflatable cervical air sac and
fat deposit in C. melanotos, and greatly
elaborated and highly colored neck plumage (ruffs) in P. pugnax. In T. subruficollis
males are slightly larger than females
(Table 2), but this is not consistently discernable in the field.
Dispersion patterns: The spacing characteristics and territorial systems of the
three species in Group IV differ considerably and require some detail in explanation.
The density of C. melanotos varies greatly
over a geographic region within a season
and in one locality in different seasons
(Pitelka, 1959; Holmes, 1966a). They typically occur in favorable years and places
at high densities. Correlated with this, territorial advertizement is accomplished by
displays that function best over short distances. These include a low flight around
the periphery of the territory, interrupted
periodically by a rise to a height of 5 to
10 m followed by a glide back to about 1 m
above the tundra. The vocalization is a
deep hooting call that does not carry far.
There is no conspicuous variant of this
display for use in sparse populations, as is
seen in C. fuscicollis.
At Barrow, population density has fluctuated widely, and territories vary inversely
in size with population density. Males will
attempt to defend females on their territories from other males. At low densities
they may succeed in this so that the breeding system is essentially polygynous or even
effectively monogamous when few females
are available. Still, the potential for promiscuous mating exists and is expressed
at higher densities.
In T. subruficollis, 2 to 10 males occur
together, each defending an area 10 to
50 m in diameter (Pitelka, Holmes, and
MacLean, unpublished). The locations of
these clusters of males forming "exploded
leks" vary from year to year and perhaps
also within a season. In contrast, males of
P. pugnax defend display stations of 1 to
3 m2, with 2 to 20 males of varying social
status on a display ground that is used
traditionally year after year (Hogan-Warburg, 1966). On the display areas of both
species males are in close proximity to each
other, and during certain periods of the
day display is intense. Communication is
mainly by means of visual signals and
involves little (T. subruficollis) or no (P.
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
pugnax) aerial component. There is no
song given by males of either species; the
only vocalizations given during display are
simple call notes. This form of display
supports the contention of Marler (1957)
that visual communication is more efficient
than auditory signals for individuals occurring in close proximity to one another.
In the absence of conspicuous vocalizations the prominent wing-flashing and
flutter-jumping of these two species probably attracts females to the lek. This may
be particularly important in T. subruficollis, in which the position of the lek
changes. The flash of light coming from
the underwing surfaces of T. subruficollis
is a conspicuous signal. The location function of displays is probably not as important in P. pugnax because of their traditional use of the same display sites.
THE EVOLUTION OF SANDPIPER
SOCIAL SYSTEMS
Larsen (1957) holds that the evolutionary divergence of calidridine sandpipers
and, we assume, their social systems as
well, took place in environments similar
to those in which they occur today. We are
thus able to evaluate the adaptive qualities
of the diverse patterns of social organization seen in this subfamily in terms of
contemporary environments and selective
forces. Our hypotheses, discussed below, are
embodied in a schematic model shown in
Figure 1.
High latitude environments
Many components of a species' environment are potential forces affecting the evolution of its social system. Verner and
Willson (1966) observed for North American passerine birds that non-monogamous
mating systems occur more frequently in
species occupying two-dimensional habitats, such as marshes and grasslands, than
in species occupying structurally more complex habitats, such as forests. A similar
correlation was found by Crook (1964) for
ploceid weavers in Africa and Asia. Since
all calidridine sandpipers breed on twodimensional habitats, either tundra or sub-
191
arctic meadow, differences in habitat structure at the gross or formational level
cannot account for the divergence of their
social systems. Similarly, since all sandpipers lay their clutches of four eggs in
shallow, mostly open cups on the ground,
the availability of nest sites (von Haartman, 1969) is not an important factor influencing sandpiper social system differences. The amount of protective cover for
the nest does, however, influence predation
rate (Holmes, 19716) and may indirectly
influence social organization.
The feature of arctic and subarctic ecosystems which probably has the greatest
potential for influencing the dispersion
patterns of breeding birds is the amount,
availability, and spatial distribution of
food. While on the breeding grounds, sandpipers are almost exclusively dependent
upon tundra arthropods, mainly insects.
The insect fauna of arctic tundra is very
low in diversity compared with faunas at
lower latitudes (Downes, 1964). Insect
orders and families that are important components of temperate latitude communities are lacking entirely or are represented
by only a few species. The order Diptera is
the most abundant and conspicuous insect group at higher latitudes, especially
the families Tipulidae and Chironomidae.
The low diversity of insects does not
necessarily imply low production; indeed,
a large biomass is typically produced by a
relatively small number of insect species.
However, changes in the abundance of one
or a few species of insects have major
effects on the total availability of food for
insectivorous birds. Such changes, some of
which are predictable while others are not,
result from (i) seasonal life cycle changes
in the insects themselves; (ii) variations in
weather which affect insect survival, growth,
and availability; and (iii) local variations
in insect abundance resulting from habitat patchiness. These have been summarized by Holmes (19666) and MacLean
and Pitelka (1971).
Of particular importance to this discussion are spatial variations or habitat patchiness. The homogeneity of the "flat, monotonous arctic tundra" is a popular
192
PITELKA, HOLMES, AND MACLEAN
- ENVIRONMENT •
FOOD-INSECTS
\
N
\
\
FLUCTUATIONS IN FOOD SUPPLY
AFFECTS
SETTLING
DENSITIES
CONSTANT
VARIABLE SPACING PATTERNS,
LOCALLY DENSE POPULATIONS IN
FAVORABLE YEARS AND PLACES
SPACING PATTERN
SMALL TERRITORIES,
FEED ELSEWHERE
WITH SAFE FOOD RESERVES
FOR 'HARD T I M E S '
.
^
\
HIGH PREDATION
INTENSITY
HIGH RATE OF
FOOD CONSUMPTION
POPULATIONS LOCALLY
CLUMPED IN GOOD
/ NESTING HABITAT
DISPERSED POPULATIONS
ONE ADULT EMANCIPATED
FROM NEST DUTIES:
OF PREDATION
TERRITORY DEFENSE
AND NEST PROTECTION
REQUIRE CONTINUAL
ATTENTION
D
2 MAY LAY
MULTIPLE
CLUTCHES
PERSISTENT RESIDENCE
OF BOTH ADULTS
MUTUAL CARE
— OF NEST AND
YOUflG BY ADULTS
PERSISTENT PAIRBOND
POSSIBILITY OF
RENESTING IF
NEST IS LOST
d* RELEASED
S
o'tf ON BETTER
TERRITORIES
ATTRACT
MULTIPLE
MATES
SECOND CLUTCH
LAID, & AND ?
INCUBATE AT
SEPARATE NESTS
¥ MATES WITH
2 - 3 <?d*
c i V REMAIN ON
TERRITORIES
I
J,
\
cf<? COMPETE FOR 2-S
2ND CLUTCH
SERIAL POLYGAMY
(3 ? SPECIES)
*
FLUID OR
L E K SPACING
* ^ COMPETE
DIRECTLY *
FOR 2 S
.. <? ABANDONS
INCUBATION
\
MONOGAMY
\
g TERRITORIES
COMPRESSED, SEPARATED
PARTLY OR WHOLLY
FROM FEEDING AND
NESTING SITES
POLYGYNY
I 3 SPECIES)
I
PROMISCUITY
13 SPECIES!
FIG. 1. Model for the evolution of social systems in
calidridine sandpipers. In response to environmental features (at top), differing strategies through
differing sets of populational characteristics adap-
tively combined lead to four different classes of
social systems (at bottom). See text for further explanation.
misconception. In actuality, the tundra is
dominated by features of micro-relief such
as frost polygons (Hussey and Michelson,
1966) which have a major influence upon
microhabitat structure and thus on insect
distribution. Their influence is magnified
by the presence of permafrost which retards drainage. MacLean (1971) and MacLean et al. (unpublished) have found differences of an order of magnitude in the
biomass of invertebrates occupying tundra
habitats separated only by a few meters.
The most productive habitats are the lowlying, and hence moist meadows and
troughs of polygonal systems; raised ridges
and portions of polygons are more xeric
and less productive. The low-lying habitats, however, are the last to emerge in
spring from the winter snow and are subject to variations in accessibility, due to
flooding at melt-off, summer snow storms,
and rains. Thus, these habitats offer the
greatest potential as a food source for
breeding birds, but also the greatest risk.
All of these factors—low prey diversity,
seasonal life cycle and weather-induced
changes in prey availability, and the mosaic pattern of insect distribution and
abundance—combine to produce a food
source for sandpipers that is characterized
by great variability in amplitude and in
predictability over both space and time
(see Fig. 1). We believe it is primarily in
response to variations in amount and dependability of the food resource, modified
by intensity of nest predation, that the
strategies embodied in the social organization of calidridine sandpipers have evolved.
Strategies of resource exploitation
The social systems of sandpipers may be
separated into two basic patterns of utilizing the variable food resource. In one,
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
considered "conservative," there is a relatively high probability of the population
producing a moderate number of surviving
offspring each breeding season (Group I
species). The second pattern, considered
"opportunistic" in the broadest sense, allows the possibility of a much greater reproductive output from the population in
some years and some places, out it may
carry with it a greater chance of reproductive failure (Group II, III and IV species).
It must be emphasized, as our definition
in the introduction implies, that these
social system strategies are established and
maintained in populations by the action of
natural selection on individual breeding
success, i.e., on the probabilities of individuals breeding successfully rather than
on total population reproductive output.
The conservative strategy. Although territory size in the 15 monogamous calidridine species varies widely, the densities
characteristic of each species remain relatively constant from one year to the next.
In those with large territories, e.g., C. alpina in northern Alaska, the defended area
provides feeding sites that are free from
competition from conspecifics; that is, the
territory offers an exclusive food reserve
that provides sufficient food for the breeding pair even during periods of food shortage. MacLean (1969) argued that territory
size in C. alpina relates more to food supply
under adverse conditions than under "normal" conditions.
This implies that the territorial system
actively distributes birds over the habitat
in relation to resources and that the wide
spacing is not simply the result of low
population size. Evidence supporting this
contention has been given by Holmes
(1970) who showed that (i) removal of
male C. alpina from the tundra near Barrow resulted in their prompt replacement
by other males, indicating that some individuals had been prevented from settling
by already established males or had settled
in less preferred areas that they were willing to vacate; (ii) in populations of C.
alpina at a lower latitude where the summer season is longer, the weather more
predictable, and the food supply more de-
193
pendable, males have smaller territories
and thus breed at higher densities; and
(iii) the spacing pattern is produced and
maintained by a strongly developed system of aggressive behavior.
The wide spacing of these populations
results in nests being placed far apart. Tinbergen et al. (1967) experimentally demonstrated a negative correlation between nest
density and predator success in a gull
colony. Since predation by jaegers (Stercorarins spp.), gulls, weasels, and foxes is
at times relatively intense in tundra communities, wide spacing of sandpiper nests
may reduce predation intensity and increase breeding success.
In such a widely spaced population,
there are definite advantages to the persistent residence of both adults which is
facilitated by the maintenance of a monogamous pairbond between them. "With
both adults participating in incubation,
the energetic cost is shared and each bird
has more time to forage. This is particularly important during periods of adverse
weather. Temperatures in arctic regions
commonly fall below freezing during the
incubation period. This reduces food
availability by inhibiting invertebrate activity and, at the same time, increases the
bird's metabolic rate and food requirement. The prolonged absence of one adult
while foraging without another to incubate would lead to severe egg chilling.
Norton (1972) has shown for calidridine
sandpipers that, while such chilling is seldom fatal, it leads to asynchronous hatching and reduced chick viability.
A different type of dispersion pattern
and territorial system occurs in some other
monogamous calidridines. In these, the
nesting density is high in a favorable habitat, and foraging by the adults occurs
away from the nesting territory, often in
nearby communal feeding areas (Soikkeli,
1967; Holmes, 1971&). The territories serve
mainly for pairing and nesting, and may
provide some degree of nest dispersion as
well. The extremely high nesting density
of C. mauri in western Alaska (Holmes,
19716) is related to patchy distribution
of suitable nesting habitat and the presence
194
PITELKA, HOLMES, AND MACLEAN
of abundant food resources nearby. Nesting occurs only on "islands" of heath tundra where low, shrubby vegetation provides
protection of nests from predators.
In these species in which the adults
leave the territory to feed, there is a chance
that another bird could move in and settle
on the territory during their absence. This
is normally prevented by the territory holders confining their activity, including feeding, to the territory during pair formation
and egg-laying. Thus, even in these species
food reserves may be important in determining territory size and nesting density. Even later in the season, there may
be a need for one adult to remain on the
territory to defend it against newly arrived
or unsettled birds. Continual occupancy o£
the territory may also protect the nest from
predators. These factors would favor the
persistent residence of both adults so that
the territory need never be left unattended.
Another advantage of the persistent residence of both adults is the added protection given the young after hatching. Although young sandpipers leave the nest
within hours after hatching and gather all
of their own food, they do require periodic
brooding by the adults for a few days before they develop full homeothermic control of body temperature. Adults also lead
their young to feeding areas, warn them
of approaching predators, and perform
distraction displays to lead predators away
from young. Holmes (1971b, 1973) holds
for C. mauri in western Alaska that the
protective role of adults toward their
young may be a very important function
of the persistent monogamous pair bond.
The fact that the majority of calidridine
species (Group I) possess a monogamous
social system indicates that it provides a
generally successful mode of exploitation
of tundra resources. Its widespread occurrence within the group, the lack of specialized anatomical or behavioral features
in the species that possess such a system,
and the similarity in associated display behavior shown by the monogamous species,
suggest to us that this is the primitive pattern of sandpiper social organization.
Before turning to the opportunistic spe-
cies, however, a cautionary note is needed.
The dichotomy conservative vs. opportunistic seems reasonable to use in our present knowledge, but already it is clear that
within what we call conservative species,
some elements of opportunism have to be
recognized. They may prove to represent
important differences among the species
of Group I. One such element is breakdown of the pairbond in relation to continuing need for parental care and, the
ecologically significant follow-up to this,
the departure of either or both sexes from
the breeding grounds while the young remain to complete their growth. Thus, in
the most conservative system known, that
of C. alpina, adults and young remain together on the breeding ground until the
onset of migration for all in August. In
C. bairdii and C. pusilla, adults and
young leave sooner. Subtle differences in
timing of pairbond dissolution and departure are now being studied in northern
Alaska, particularly by Safriel. In C. mauri
the dense populations reported by Holmes
(1972) depart from the breeding grounds
mainly by mid-July (adults) or mid-August
(young of the year). This species takes yet
another step toward opportunism in the
communal use of feeding areas while maintaining a monogamous pair bond and a
territory that provides some of its food.
Thus, the conservative features of social
systems among Group I species are not
consistently shared, and a trend toward
opportunism is seen in two of them: (i) the
shortening of time over which especially
adults, but also their young depend on
habitat resources of the breeding area; and
(ii) the supplementing of the food supply
of a territory with that of adjacent areas
shared with neighboring territory holders.
These features of conservative systems deserve special attention in future studies.
The opportunistic strategy. In a number
of species with non-monogamous social systems, densities and reproductive effort vary
greatly in both space and time. We suggest
that the distribution of breeding intensity
in these populations corresponds with
locally favorable environmental conditions,
in particular, the peaks of food abundance.
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
This opportunistic exploitation can be accomplished in several ways. Newly arrived
sandpipers might move about the tundra
regardless of topography in search of an
area of abundant food and settle only when
such an area is found. Alternatively, the
birds might take advantage of the patchiness which is produced by topographic
variation of the tundra. As developed
above, birds adopt conservative strategy
typically to occupy territories large enough
to provide sufficient food even during adverse conditions, with the partial exception
of C. mauri already discussed above. In
contrast, the opportunistic strategy is to
occupy small territories packed into the
more productive lowland marshy habitat,
balancing the risk of breeding failure in
the event of adverse weather against the
probability of a very successful breeding
effort if conditions remain favorable. This
strategy may be used only if the marshes
become exposed early in the summer when
the birds are arriving, establishing territories, and beginning to breed. Thus, yearto-year variation in the timing and pattern
of snow may be an important determinant
of breeding density at any point in the
breeding range.
Another form of opportunism which relates breeding density to favorable conditions was described by MacLean (1969) for
C. melanotos. This species is opportunistic
both in exploiting the peaks of the resource
distribution pattern and in avoiding the
lows, the periods of temporary food shortage brought on by bad weather. It does
this by carrying large fat stores which it
obtains during the late stages of northward
migration; these are then utilized during
the periods of adverse weather conditions
on the tundra in early summer. Bv avoiding temporary periods of food shortage,
birds of this species are better able to pile
up the remarkably high breeding densities
recorded in some years (Pitelka, 1959;
Holmes, 1966a). Variations in breeding density, then, may be related both to food conditions on the tundra and to conditions
along the migratory route affecting the
ability of the birds to deposit the necessary
energy reserves before reaching the tundra.
195
Whatever the mechanisms involved,
most, if not all, of the opportunistic species do have clumped dispersion patterns
and do nest intermittently at high densities. Since these conditions increase the
vulnerability of nests to predators, selective
pressures for nest crypticity must be extremely strong (Fig. 1). Those species that
do nest in locally dense populations, especially C. fiiscicollis and C. melanotos in
our experience, rely more on cryptic behavior around the nest than do those species that typically nest in sparser populations. The crypticity of nests in dense
populations is also enhanced by the reduction in number of trips made to and from
the nest by the incubating adult(s). In fact,
we hypothesize that the absence of one
adult from the nest in the opportunistic
species is, at least in part, an adaptation
for reducing the conspicuousness of the
nest in such populations. Likewise, Brown
(1964) hypothesized for grouse that predation pressure, especially in open habitats,
would be a strong selective factor acting to
free one adult from nest-care responsibilities.
For sandpipers in high latitude environments, a one-adult incubation system
would be successful only when food density
is high. Such a system places the energetic
burden of incubation on a single bird, and,
at the same time, limits the amount of time
available for foraging by that individual.
Norton (1972) found that female C. melanotos incubate their eggs 85% of the time,
compared with 96% and 97% in the shared
incubation of C. bairdii and C. alpina,
respectively.
In addition to reducing the conspicuousness of the nest to predators, removal of
one adult from the vicinity of the nest may
have another advantage. In areas of high
nesting density, breeding success might be
enhanced by a reduction of the number
of birds consuming the food resource. The
early departure of one bird from the nest
area would reduce the rate of food consumption on the breeding area, leaving
more for the remaining incubator and
later for the young fPitelka, 1959). Thus,
both the pressure of predation and con-
196
PITELKA, HOLMES, AND MACLEAN
sumption of resources that are potentially logically distant species suggests that it has
in short supply may select for the removal evolved independently on several occasions.
of one member of the pair from the area of The relationship of the first male to the
the nest as soon as possible. This can only second clutch may well differ in the sevbe accomplished by shortening the dura- eral species.
tion of the pairbond and reducing, or inIf, in contrast to the above, the sex that
deed eliminating, the parental responsibili- is emancipated from nest duties is the male,
ties of one adult.
there would be greater opportunity for
With selection promoting the removal the sexes to diverge in behavior and morof one adult from the vicinity of the nest, phology. In particular, cryptic coloration
the possibility of sequentially repeated and behavior are selected for in incubating
matings arises for the emancipated sex females, while in. males that have no nest
(Fig. 1). The advantages to a short pair- duties, these features are of less adaptive
bond make no distinction as to which sex value. Instead, features that contribute to
is relieved of nest duties. In the monoga- success in obtaining a territory and atmous sandpipers, there is a tendency, for tracting females for mating are favored.
example, in C. pusilla (Safriel and Soikkeli, The stage is set for the operation of sexual
personal communication) and in C. alpina selection, which can be a potent force in
in coastal Finland (Soikkeli, 1967) for the the evolution of sexual dimorphism (Selanfemale to leave after hatching, with the der, 1965, 1972) and of elaborate and
male tending the brood alone until fledg- highly ritualized display behavior.
ing. If it is the female that leaves the nest,
Jehl (1970) presented evidence that the
the possibility of repeat nesting with a new slight size dimorphism between the sexes
mate is normally opposed by the energetic in two monogamous calidridine species
cost of egg formation. MacLean (I9601) facilitates early pairing and may contribute
showed that female sandpipers lose body to reproductive success. Other authors have
fat during the egg-laying period and have related dimorphism to the subdivision of
less fat during incubation than at any other feeding niche, thus reducing intra-pair
time of the season. A bird bee^nnine a nest competition (Selander, 1966). Neither of
attempt in such a condition would not these factors indicates a particular direchave a his:h probability of success.
tion of dimorphism. In the monogamous
Nevertheless, repeat nestings do occur in and serially polygamous sandpipers, fesome of the monogamous species following males are slightly, but consistently, larger
loss of a nest to a predator (Holmes, 1966a, than males (Table 2). In C. fuscicollis and
1972; Soikkeli, 1967). Repeat nestings have C. ferruginea, sexual selection favoring
a much higher frequency of three- and males has perhaps proceeded only far
even two-egg clutches than do first nest- enough to begin a reversal of the primitive
ings; this may be due to energetic limita- female-larger pattern. The advantage of
tion, but also to hormonal or some other rapid mating, which would be favored in
these species, is achieved through beform of systemic limitation.
havioral
means and, in C. ferruginea,
The capacity for repeat nesting and the
tendency of the female to be relieved of through color dimorphism. Dimorphism
duties at a first nest provide possible ave- is more pronounced in the promiscuous
nues for the evolution of serial polvgamy. CGroup IV) than in the polygynous (Group
Such an arrangement could evolve directly III) species (Table 2). Indeed, the difrom a monogamous svstem through the morphism in C. melanotos and P. pugnax
laying of a second clutch by a monogamous is considerably greater than is indicated in
pair, or from a polygamous system in the table due to conspicuous secondary sex
which females are emancipated from nest characteristics. Tryngitcs subruficoUis, alduties and available to mate with other though promiscuous, is less dimorphic in
males. The fact that this system appears size and essentially monomorphic in plumin two or three geographically and eco- age. This species inhabits barren and
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
sparsely vegetated high-latitude tundra
where large and conspicuous males might
be subject to increased predation. In this
habitat cryptic coloration may be adaptive
for both sexes, and elaborate, but concealable, behavioral display has evolved
rather than conspicuous morphology.
The actual pattern of social organization
may be the evolved response to conflicting
selective pressures with respect to what is
advantageous for the male vs. the female.
Thus, Downhower and Armitage (1971)
have shown that polygyny may be advantageous to males, while females have higher
fitness (greater reproductive output) in
monogamous situations. In this case, we
would expect males to evolve characteristics favoring multiple mating, while females should evolve characteristics such as
avoidance or aggression to minimize the
effect of other females on their own reproductive success, i.e., to breed in a monogamous-like situation. This concept may have
an important bearing on the evolution of
lek spacing and promiscuous mating from
a territorial, polygynous social system such
as certain sandpipers exemplify.
In a lek system, males with a favorable
combination of characteristics—morphology, display behavior, display site, etc.—
are able to reap the profits of repetitive
mating. At the same time, females leave
the lek to nest and are free to place the
nest in an optimal site away from other
females and without regard for the characteristics which may have led the males
to display on a particular site. They are
not adversely affected by repeat matings
by the male. In the territorial, polygynous
svstem, in contrast, nest-site selection is
limited to the territory of the male, and
each additional matins: by the male increases food consumption, nest density, and
conspicuousness of the territory to predators.
Two factors promote the numerical stability of a lek system as opposed to the
territorial, polyerynous svstem. First, in the
lek of P. bugnax, the display arenas are
traditionally occupied locations, but the
females may change the nest locations from
year to year in response to local changes
197
in food density. Data on the nesting locations of P. pugnax associated with particular leks in a series of years are urgently
needed, as are data on the relative permanence of leks at arctic latitudes in the
U. S. S. R. as against leks at temperate
latitudes in western Europe. Second, the
mathematical model developed by Downhower and Armitage (1971) shows that the
sensitivity of optimal harem size to changes
in environmental conditions varies in relation to the change in fitness that occurs
with the addition of one female to the
harem. In the territorial, polygynous system, the addition of one female probably
has a real effect upon the reproduction
(fitness) of other females on the territory;
such a system is sensitive to environmental
variation, especially that of food supply.
In a lek system, where additional matings
do not influence a male's previous mates,
the system is less sensitive to environmental
variation. Thus, we expect (and find) great
variation in nesting density in the territorial, polygynous (Group III) and promiscuous (C. melanotos) species, while density is relatively stable in P. pugnax. More
data are needed for T. subruficollis from
the main area of its breeding distribution
in arctic Canada; near Barrow, this species,
breeding at or near its western limits,
varies widely in abundance and is common only in occasional years.
These observations lead us to the conclusion that lek spacing is a natural and
not at all surprising derivative of a territorial, polygynous social system. Such a system requires the total loss of the pairbond,
and adaptations facilitating rapid mating
should be highly favored. In these species,
the displays associated with matin? are
elaborated. The exaggerated posturing of
male P. finenax on the lek is well known.
T. subruficollis on their "exploded leks"
combine active wing waving, a display
seen in less exaggerated form in most calidridines, with flutter jumping (Pitelka,
Holmes, and MacLean, unpublished) similar to that performed by P. pugnax. In
addition, the freouency of interactions is
increased by tbe hief) pooulation density
of the clumped species, offering more op-
198
PITELKA, HOLMES, AND MACLEAN
portunities for mating and maintaining
reproductive activity at a high level.
CONCLUSION
Thus, the social systems exhibited by
calidridine sandpipers can be separated
into four basic patterns, each representing
an adaptive strategy evolved primarily in
response to the highly variable and unpredictable tundra resources but also modified
through other selective pressures such as
predation.
The conservative approach, taken by the
majority of calidridine species, provides
adequate resources for a pair and its brood
even during adverse conditions. The strategy is to disperse on large territories which
provide adequate food or on small territories in favorable nesting habitat with additional food obtained from communally
used areas nearby. In either case, the evolutionary result is the persistent residence
of both sexes and a monogamous pairbond.
The results of opportunism exhibited by
other calidridine species are three different
patterns of social organization. They are
related by the fact that all three have
evolved in response to locally favorable
environments patchy in their distribution.
In the serially polygamous approach, the
female is freed from incubating the first
clutch, allowing her to mate again with the
same or a different male to produce a second clutch of eggs. In this case, reproductive output is directly increased. In the
polygynous species, males that occupy territories in high quality habitat maintain
pairbonds with several females and produce, in good seasons, a large number of
young. In the promiscuous species, the
spacing pattern is more fluid; the territories serve mainly for mating, although
in C. melanotos they do provide a feeding
area for the male during his period of territorial activity. The increase in sexual
dimorphism and the dissolution of the pair
relationship in this latter group are consequences of dense populations, increased
predation pressure, loss of food function
for the territory, and divergent selective
pressures acting upon males and females.
All of these features and their causal factors
are interrelated and cannot easily be separated. They form a mutually reinforcing
complex by which each species has become
adapted to its environment.
APPENDIX
TABLE 1. A summary of breeding system characteristics of calidridine sandpipers.
Incubating
sex(es)
Nest
scrape6
Territorial and spacing patterns
of males
Advertisement
displays
Song
types
Sources*
Group I Species
Calidris alpina* (H)«
M-(-F
-f
High flight.
hovering,
5-50 m above
tundra
Trills
19,22,23,53
C. canutus* (H)
M-f F
?
Large territories (6/40 ha at
Barrow; 30/40 ha in western
Alaska; 16/40 ha in Finland);
include nesting and at Barrow
all feeding areas
Large territories; males spaced
far apart
High flights,
periodic
hovering,
50-100 m up
Whistlelike, farcarrying
39,43
Plaintive
whistle; trill
Trills
Trills
15,32,47
32
36,42
Trills
6,30,60
Trills,
whistle
Trills
9,14,16
26,34
Trills
10,13,39
Trills
7,8,24,25
Trills
54,55
Trills and
whistles
Trills
29,39
Trills
Trills
60
Trills
18,20,56
Trills
37,38,46
Trills
15,18,31,52
C. tenuirostris (P)
M(-)-F?)
?
No information
C. subminuta (P)
C. ruficollis* (P)
M-f F
M-j-F
?
-f
No information
No information
C. maritima* (NAtl)
M-f-F
-f
Dispersed evenly over tundra
C. ptilocnemis* (NPac)
M-f F
?
C. minutilla* (N)
M-fF
-f
C. bairdii* (N)
M-fF
-f
C. mauri* (N)
M-f F
-f
C. pusilla* (N)
M-f-F
-f
Micropalama
himantopus (N)
Eurynorhynchus
pygmaeus (P)
Limicola falcinellus (P)
Aphriza virgata* (N)
M-f F
?
Dispersed widely over available
tundra
Evenly spaced (1/2 ha) in
marsh-bog habitat
Evenly spaced in well-drained
habitat near coast or in
mountains (Alaska)
Densely packed on upland habitat
surrounded by marsh
Evenly spaced but dense on
drained tundra near coast and
along rivers
Pairs spaced
M(-f F?)
+
No information
M-f F
M(-f F?)
?
?
No information
Pairs spaced far apart on
barren mountain ridges
Group II Species
C. temminckii (P)
M-f F
-f
C. aiba* (H)
M-f F
-f
C. minuta (P)
M-f F
?
Males on small territories,
often along lakes or coast
Widely scattered on high arctic
tundra; dispersion may be clumped
Widely scattered
?
?
Hovering
flight; glides
Hovering, gliding, up to 35 m
Hovering
flight
High hover
flight
High hover
flight
Flights to 20 m,
little hovering
Hovering
flights
to 50 m
Hovering and
fast flights
High flights,
hovering
High flight
High flight
Hovering
flight
Hovering
flight
Hovering flight
</>
11,48,50
12,33
g**>
r
O
S
z
d
o
z
>
V.
a
o
s
Group III Species
C. fuscicollis* (N)
Fonly
C. jerruginea* (P)
Fonly
C. acuminata (P)
Fonly
Variably sized territories
containing one or more nests
and most feeding areas
Variably sized territories
with one or more nests and most
feeding areas
Apparently large territories (?);
little information
High hovering
flight and
low flight
Low flight
and gliding
Trills and
whistles
13,28,40,57
Trills and
whistles
17,27.45,49
Gliding flight;
no hovering
Hollow trill;
ringing call
32,59
Males on variably sized territories, often small, include
most feeding sites for male;
may or may not include nest(s)
Groups of 2-10 males on clumped
display sites; females feed and
nest at variable distances, not
on male territories
Groups of 2-20 males on small
traditional display sites;
feeding and nesting elsewhere
Low, fast
flight
Hollow
hooting
41,51
Wing-flashing,
low jumps,
low flutter
No song,
only call
note
35,44,58
nignt
No song.
only call
note
1,2,3,4,5,21
o
Group IV Species
C. melanotos* (N-P)
Fonly
Tryngites
subruficollis* (N)
F only
Philomachus pugnax (P)
F only
Wing-flashing,
other wing
actions, low
jumps, no flight
display
• Species observed in the breeding season by Pitelka, Holmes, and/or Mac Lean.
•b Breeding distribution: H, holarctic; N, Nearctic; P, Palearctic; NAtl, North Atlantic rim and islands;
Nest-scraping recorded for species (-)-), highly developed (-)—(-), absent from display repertoire (—).
c
Key to sources:
1—Andersen (1944)
21—Hogan-Warburg (1966)
22—Holmes (1966a)
2—Andersen (1948)
23—Holmes (1970)
3—Andersen (1951)
24—Holmes (19716)
4—Banckc and Meesenburg (1952)
25—Holmes (1973)
5—Bancke and Meesenburg (1958)
26—Holmes (unpublished)
6—Bengston (1970)
27—Holmes and Pitelka (1964)
7—Brandt (1943)
28—Holmes and Pitelka (unpublished)
8—Brown (1962)
29—Jehl (1973)
9—Conover (1945)
30—Keith (1938)
10—Dixon (1917)
31—Kistchinski (pers. comm.)
11—Dixon (1918)
32—Kozlova (1962)
12—Dixon (1927)
33—MacLean (unpublished)
13—Drury (1961)
34—Moore (1912)
14—Fay and Cade (1959)
35—Oring (1964)
15—Grote (1937)
36—Palmer (1967)
16—Hanna (1921)
37—Parmelee (1970)
17—Haviland (1915)
38—Parmelee and MacDonald (1960)
18—Haviland (1916)
39—Parmelee et al. (1967)
19—Hcldt (1966)
40—Parmelee et al. (1968)
20—Hilden (1965)
id
3
NPac, North Pacific rim and islands.
41—Pitelka (1959)
42—Pitelka (unpublished)
43—Pitelka and Holmes (unpublished)
44—Pitelka, Holmes and MacLean (unpublished)
45—Pitelka and Remsen (unpublished)
46—Pleske (1928)
47—Portenko (1933)
48—Portenko (1957)
49—Portenko (1959)
50—Portenko (I960)
51—Portenko (1968)
52—Rutilevskii (1963)
53—Soikkeli (1967)
54—Soikkeli and Safriel (pers. comm.)
55—Soper (1946)
56—Southern and Lewis (1938)
57—Sutton (1932)
58—Sutton (1967)
59—Vorobiev (1963)
60—Witherby et al. (1940)
o3
S
>
a
>
Z
201
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
TABLE 2. Sexual dimorphism of calidridine sandpipers as indicated by length of wing.
Ratio
(M/F)
0.97
Source1
0.95
K
0.99
D
0.98
O
0.98
K
0.96
K
0.98
R
0.98
J
0.97
R
0.98
R
0.97
R
0.98
J
0.96
K
0.98
D
0.97
R
94.5
96.6
118.6
121.9
95.1
95.4
0.98
K
0.97
K
1.0
K
117.0-122.5
116.5-124
123 -132
121 -133
122 -140
122 -135
119.7
120.3
126.6
127.7
0.99
R
0.99
D
131.6
127.5
1.04
D
138.2-147.0
118.8-136.0
127 -133
120 -128
171.5-186
148 -154
141.3
126.6
130.9
122.8
181.6
151.2
1.12
K
1.07
O
1.20
R
Group I Species
Sex
N
Range (mm)
Mean
Calidris a. alpina
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
M
F
15
14
19
12
10
16
9
5
17
15
12
11
18
7
109.0-113.0
110.0-117.8
151.0-165.0
160.2-174.0
174 -190
173 -190
88 - 93
86 - 92
96.5-104.3
95.0-106.0
119.2-126.7
124.8-130.2
119.0-133.0
122.0-134.5
83 - 92
84 - 94
114 -122
119 -126
91 - 99
90 - 99.5
88 - 98.5
92 -101.5
122 -133
128 -137
94.6-100.6
100.0-102.0
94 -107
102 -110
164 -183
169 -181
110.0
114.2
158.9
167.4
181.3
183.0
88.9
90.6
98.4
99.9
122.9
128.0
126.5
129.2
86.8
88.7
118.7
122.3
94.6
96.4
93.9
96.5
129.1
132.2
97.3
101.0
103.5
105.4
170.9
176.0
M
F
M
F
M
F
30
30
30
30
50
30
90.3-100.2
91.0-101.9
115.0-124.0
115.0-126.7
87.5- 97.0
90.4- 98.5
M
F
M
F
M
F
12
2
26
35
26
17
M
F
M
F
M
F
18
26
15
9
10
9
Calidris canutus
Calidris tenuirostris
Calidris subminuta
Calidris ruficollis
Calidris maritima
C. p. ptilocnemis
Calidris minutilla
Calidris bairdii
Calidris mauri
Calidris pusilla
Micropalama himantopus
Eurynorhynchus pygmaeus
Limicola f. falcinellus
Aphriza virgata
Group II Species
Calidris temminckii
Calidris alba
Calidris minuta
Group III Species
Calidris fuscicollis
Calidris ferruginea
Calidris acuminata
Group IV Species
Calidris melanotos
Tryngites subruficollis
Philomachus pugnax
27
41
41
9
9
12
11
11
13
29
29
9
2
11
14
10
K
• Key to sources: D, Dement'ev et al. (1951 [1969 translation]); J, Jehl (1970); K, Kozlova (1962);
O, original data from specimens in Museum of Vertebrate Zoology, Univ. of California, Berkeley;
R, Ridgway (1919).
REFERENCES
Andersen, F. S. 1944. Contributions to the breeding
biology of the ruff (Philomachus pugnax). Dan.
Omithol. Foren Tidsskr. 36:26-30.
Andersen, F. S. 1948. Contributions to the biology
of the ruff (Philomachus pugnax L.). Part II. Dan.
Ornithol. Foren Tidsskr. 42:125-148.
Andersen, F. S. 1951. Contributions to the biology
of the ruff (Philomachus pugnax L.). Part III.
Dan. Ornithol. Foren Tidsskr. 45:145-173.
Bancke, P., and H. Meesenburg. 1952. A study of
202
PITELKA, HOLMES, AND MACLEAN
the display of the ruff (Philomachus pugnax L.).
Ban. Ornithol. Foren Tiddskr. 46:98-109.
Bancke, P., and H. Meesenburg. 1958. A study of the
display of the ruff (Philomachus pugnax L.). II.
Dan. Ornithol. Foren Tidsskr. 52:118-141.
Bartholomew, G. A. 1970. A model for the evolution
of pinniped polygyny. Evolution 24:546-559.
Bengston, S. A. 1970. Breeding behaviour of the
Purple Sandpiper, Calidris maritima, in west
Spitsbergen. Ornis Scand. 1:17-25.
British Ornithologists' Union. 1952. Checklist of the
birds of Great Britain and Ireland. London.
Brandt, H. 1943. Alaska bird trails. Bird Research
Foundation, Cleveland, Ohio.
Brown, J. L. 1964. The evolution of diversity in
avian territorial systems. Wilson Bull. 76:160-169.
Brown, R. G. B. 1962. The aggressive and distraction behaviour of the Western Sandpiper, Ereunetes mauri. Ibis 104:1-12.
Conover, B. 1945. Notes on some American shorebirds. Condor 47:211-214.
Crook, J. H. 1964. The evolution of social organization and visual communication in the weaverbirds (Ploceinae). Behaviour Suppl. 10:1-178.
Crook, J. H. 1965. The adaptive significance of avian
social organizations. Symp. Zool. Soc. London 14:
181-218.
Crook, J. H. 1970. Social organization and the environment: aspects of contemporary social ethology.
Anim. Behav. 18:197-209.
Dement'ev, G. P., N. A. Gladkov, and E. P. Spangenberg. 1951. Birds of the Soviet Union. Vol. III.
Translation published 1969 by Israel Program for
Scientific Translations, Jerusalem.
Dixon, J. S. 1917. The home life of the Baird Sandpiper. Condor 19:77-84.
Dixon, J. S. 1918. The nesting grounds and nesting
habits of the Spoon-billed Sandpiper. Auk 35:
387-404.
Dixon, J. S. 1927. The surf-bird's secret. Condor 29:
3-16.
Downes, J. A. 1964. Arctic insects and their environment. Can. Entomol. 96:279-307.
Downhower, J. F., and K. B. Armitage. 1971. The
yellow-bellied marmot and the evolution of polygamy. Amer. Natur. 105:355-370.
Drury, W. H., Jr. 1961. The breeding biology of
shorebirds on Bylot Island, Northwest Territories,
Canada. Auk 78:176-219.
Fay, F. H., and T. J. Cade. 1959. An ecological analysis of the avifauna of St. Lawrence Island, Alaska.
Univ. Calif. Publ. Zool. 63:73-150.
Grote, H. 1937. Zur Fortpflanzungsbiologie einiger
Strandlauferarten (Calidris). Beitr. Fortspfl. Vogel
13:127-132.
Haartman, L. von. 1969. Nest-site and evolution of
polygamy in European passerine birds. Ornis
Fenn. 46:1-12.
Hanna, G. D. 1921. The Pribilof Sandpiper. Condor
23:50-57.
Haviland, M. D. 1915. Notes on the breeding habits
of the Curlew Sandpiper. Brit. Birds 8:178-183.
Haviland, M. D. 1916. Notes on the breeding of
Temminck's Stint. Brit. Birds 10:157-165.
Hays, H. 1973. Polyandry in the Spotted Sandpiper,
Actitis macularia. Living Bird 12: (In press).
Heldt, R. 1966. Zur Brutbiologie des Alpenstrandlaufers, Calidris alpina schinzii. Corax 1:173-188.
Hilden, O. 1965. Zur Brutbiologie des Temminckstrandlaufers, Calidris temminckii (Leisl.). Ornis
Fenn. 42:1-5.
Hogan-Warburg, A. J. 1966. Social behaviour of the
ruff, Philomachus pugnax L. Ardea 54:109-229.
Holmes, R. T. 1966a. Breeding ecology and annual
cycle adaptations of the Red-backed Sandpiper
(Calidris alpina) in northern Alaska. Condor 68:
3-46.
Holmes, R. T. 19666. Feeding ecology of the Redbacked Sandpiper (Calidris alpina) in arctic
Alaska. Ecology 47:32-45.
Holmes, R. T. 1966c. Molt cycle of the Red-backed
Sandpiper (Calidris alpina) in western North
America. Auk 83:517-533.
Holmes, R. T. 1970. Differences in population density, territoriality, and food supply of dunlin on
arctic and subarctic tundra. Symp. Brit. Ecol. Soc.
10:303-319.
Holmes, R. T. 1971a. Latitudinal differences in the
breeding and molt schedules of Alaskan Redbacked Sandpipers (Calidris alpina). Condor 73:
93-99.
Holmes, R. T. 19716. Density, habitat, and the mating system of the Western Sandpiper (Calidris
mauri). Oecologia 7:191-208.
Holmes, R. T. 1972. Ecological factors influencing
the breeding season schedule of Western Sandpipers (Calidris mauri) in subarctic Alaska. Amer.
Midland Natur. 87:472-491.
Holmes, R. T. 1973. Social behaviour of breeding
western sandpipers (Calidris mauri). Ibis 115:
107-123.
Holmes, R. T., and F. A. Pitelka. 1964. Breeding
behavior and taxonomic relationships of the Curlew Sandpiper. Auk 81:362-379.
Holmes, R. T., and F. A. Pitelka. 1968. Food overlap
among co-existing sandpipers on northern Alaskan
tundra. Syst. Zool. 17:305-318.
Hussey, K. M., and R. W. Michelson. 1966. Tundra
relief features near Point Barrow, Alaska. Arctic
19:162-184.
Jehl, J. R., Jr. 1968. Relationships in the Charadrii
(shorebirds): a taxonomic study based on color
patterns of the downy young. Mem. San Diego
Soc. Natur. Hist. 3:1-54.
Jehl, J. R., Jr. 1970. Sexual selection for size differences in two species of sandpipers. Evolution 24:
311-319.
Jehl, J. R., Jr. 1973. Breeding biology and systematic
relationships of the Stilt Sandpiper. Wilson Bull.
85:115-147.
Keith, D. B. 1938. Observations on the Purple Sandpiper in North East Land. Proc. Zool. Soc. London 108A: 185-194.
Kistchinski, A. A., and V. E. Flint. 1973. [A case of
"double nesting" in the little stint (Calidris minuta)], p. 56-57. In Fauna and ecology of waders.
SOCIAL ORGANIZATION IN ARCTIC SANDPIPERS
Vol. 1. Moscow Univ. Press, Moscow, USSR. (In
Russian)
Kozlova, E. V. 1962. [Fauna of the U.S.S.R.—Charadriiformes, Limicolae.] Moscow.
Lack, D. 1968. Ecological adaptations for breeding
in birds. Methuen, London.
Larsen, S. 1957. The suborder Charadrii in arctic
and boreal areas during the Tertiary and Pleistocene. Acta Vertebratica 1:1-84.
MacLean, S. F., Jr. 1969. Ecological determinants of
species diversity of arctic sandpipers near Barrow.
Alaska. Ph.D. Thesis. Univ. of California, Berkeley.
MacLean, S. F., Jr. 1971. Population ecology and
energetics of tundra soil arthropods, p. 126-133.
In The structure and function of the tundra ecosystem. Vol. I. U.S. Tundra Biome Program.
MacLean, S. F., Jr., and R. T. Holmes. 1971. Bill
lengths, wintering areas, and taxonomy of North
American dunlins, Calidris alpina. Auk 88:893901.
MacLean, S. F., Jr., and F. A. Pitelka. 1971. Seasonal
patterns of abundance of tundra arthropods near
Barrow. Arctic 24:19-40.
Marler, P. 1957. Specific distinctiveness in the communication of signals of birds. Behaviour 11:13-39.
Moore, R. T. 1912. The Least Sandpiper during the
nesting season in the Magdalen Islands. Auk 29:
210-223.
Norton, D. W. 1972. Incubation schedules of four
species of calidridine sandpipers at Barrow,
Alaska. Condor 74:164-176.
Orians, G. H. 1961. The ecology of Blackbird (Agelaius) social systems. Ecol. Monogr. 31:285-312.
Orians, G. H. 1969. On the evolution of mating systems in birds and mammals. Amer. Natur. 103:
589-603.
Oring, L. W. 1964. Displays of the Buff-breasted
Sandpiper at Norman, Oklahoma. Auk 81:83-86.
Oring, L. W., and M. L. Knudson. 1973. Monogamy
and polyandry in the Spotted Sandpiper. Living
Bird 12: (In press).
Palmer, R. S. 1967. Species accounts, p. 212-243. In
G. D. Stout [ed.], The shorebirds of North America. The Viking Press, New York.
Parmelee, D. F. 1970. Breeding behavior of the
Sanderling in the Canadian high arctic. Living
Bird 9:97-146.
Parmelee, D. F., D. W. Greiner, and W. D. Graul.
1968. Summer schedule and breeding biology of
the White-rumped Sandpiper in the central Canadian arctic. Wilson Bull. 80:5-29.
Parmelee, D. F., and S. D. MacDonald. 1960. The
birds of west-central Ellesmere Island and adjacent areas. Bull. Nat. Mus. Can. 169:1-103.
Parmelee, D. F., and R. B. Payne. 1973. On multiple
broods and the breeding strategy of arctic sanderlings. Ibis 115:218-226.
Parmelee, D. F., H. A. Stephens, and R. H. Schmidt.
1967. The birds of southeastern Victoria Island
and adjacent small islands. Bull. Nat. Mus. Can.
222:1-229.
Peters, J. L. 1934. Check-list of birds of the world.
203
Vol. II. Harvard Univ. Press, Cambridge, Mass.
Pitelka, F. A. 1959. Numbers, breeding schedule,
and territoriality in Pectoral Sandpipers of northern Alaska. Condor 61:233-264.
Pitelka, F. A. 1969. Evolution of social organization
in arctic sandpiper populations. Xlth International Ethological Conf. (Rennes, France), Summaries Supplement No. 7.
Pleske, T. 1928. Birds of the Eurasian tundra. Mem.
Boston Soc. Natur. Hist. 6:111-485.
Portenko.. L. 1933. [Some new materials adding to
the knowledge of breeding ranges and life history
of the eastern Knot, Calidris tenuirostris (Horsf.).]
Arctica 1:75-98. (In Russian)
Portenko, L. 1957. Studien an einigen seltenen Limicolen aus dem nordlichen und ostlichen Sibirien.
I. Die Loffelschnepfe—Eurynorhynchus pygmaeus
L. J. Ornithol. 98:454-466.
Portenko, L. 1959. Studien an einigen seltenen Limicolen aus dem nordlichen und ostlichen Sibirien.
II. Der Sichelstrandlaufer—Erolia ferruginea (Pontopp.). J. Ornithol. 100:141-172.
Portenko, L. 1960. Ornithological explorations in
north-eastern Asia, p. 615-620. Proc. XII Int Ornithol. Congr. 1958.
Portenko, L. 1968. Studien an einigen seltenen Limicolen aus dem nordlichen und ostlichen Sibirien.
III. Der Graubruststrandlaufer—Heteropygia melanotos (Vieill.). J. Ornithol. 109:96-115.
Ridgway, R. 1919. The birds of north and middle
America. Part VIII. Government Printing Office,
Washington, D.C.
Rutilevskii, G. L. 1963. [Birds of Stobolov Island.]
Trudy Arkticheskogo i Anarkticheskogo Navchnoissled Inst, 224:93-117. (In Russian, translation
made available by R. S. Palmer)
Selander, R. K. 1965. On mating systems and sexual
selection. Amer. Natur. 99:129-141.
Selander, R. K. 1966. Sexual dimorphism and differential niche utilization in birds. Condor 68:113151.
Selander, R. K. 1972. Sexual selection and dimorphism in birds, p. 180-230. In B. Campbell [ed.].
Sexual selection and the descent of man. Aldine
Publ. Co., Chicago.
Soikkeli, M. 1967. Breeding cycle and population
dynamics in the dunlin (Calidris alpina). Ann.
Zool. Fenn. 4:158-198.
Soper, J. D. 1946. Ornithological results of the Baffin Island expeditions of 1928-1929, and 19301931, together with more recent records. Auk 63:
223-239.
Southern, H. N., and W. A. S. Lewis. 1938. The
breeding behaviour of Temminck's Stint. Brit.
Birds 31:314-321.
Sutton, G. M. 1932. The birds of Southampton Island. Mem. Carnegie Mus. 12:1-275.
Sutton, G. M. 1967. Behaviour of the Buff-breasted
Sandpiper at the nest. Arctic 20:3-7.
Tinbergen, N., M. Impekoven, and D. Franck. 1967.
An experiment on spacing-out as a defence against
predation. Behaviour 28:307-321.
Verner, J., and M. F. Willson. 1966. The influence
204
P I T E L K A , H O L M E S , AND M A C L E A N
of habitats on mating systems of North American
passerine birds. Ecology 47:143-147.
Vorobiev, K. A. 1963. Ptitsy Yakutii. Publ. Acad. of
Science, USSR, Moscow.
Witherby, H. F., F. C. R. Jourdain, N. F. Ticehurst,
and B. W. Tucker. 1940. The handbook of British
birds. Vol. 4. H. F. and G. Witherby Ltd., London.