April 1994]
Short
Communications
andCommentaries
grey Shrikeand the ecologicalimplicationsof its
impaling prey. M.S. thesis,Ben-GurionUniv. of
the Negev, Beer-Sheva,Israel.
YOSEF,R. 1993. Influence of observationposts on
territory size in Northern Shrikes.Wilson Bull.
105:180-183.
469
Loggerhead Shrikes: A ptilochronology approach. Conserv. Biol. 6:447-449.
YOSEF,
R., ANDT. C. GRIJBB,
JR. 1993. Effectof vegetation height on hunting behavior and diet of
Loggerhead Shrikes. Condor 95:127-131.
YOSELR., J. N. L^YNE,ANt) F. E. LOHRF•. 1993. Trends
YOSEF,R., W. A. MITCHELL, ^ND B. PINSHOW. 1991.
in numbersof LoggerheadShrikeson roadside
The proximatecostsand benefitsof polygyny to
censusesin peninsular Florida, 1974-1992. Fla.
male Northern
Sci. 57:28-33.
Shrikes. Wilson Bull. 103:146-149.
YOSEF,
R., ANDT. C. GRIJBB,
JR. 1992. Territory size
influencesnutritional conditionin non-breeding
Received
9 November
1992,accepted
I July1993.
The Auk 111(2):469-475, 1994
Behavior, Vocalizations, and PossibleRelationshipsof Four
Myrmotfierula Antwrens (Formicariidae) from Eastern Ecuador
BRET M.
WHITNEY
Field GuidesIncorporated,
P.O. Box 160723,Austin,Texas78716, LISA
(FootThe genus Myrmotherula,
as currently recognized westernNapo Province,Ecuador:M. spodionota
hill Antwren); M. behni(Plain-winged Antwren); M.
(Sibley and Monroe 1990), comprises31 speciesof
small, insectivorous antbirds, many of which have
sunensis
(Rio SunoAntwren); and M. schisticolor
interior
restricted geographicdistributions.Myrmotherula (Slaty Antwren).
Methods.--All observations and tape recordings
reachesits greatestdiversityat approximately400-m
elevation
near the base of the Andes in western
Ama-
were made between 27 and 30 March 1990, and be-
zonia between about 2øNand 13•Slatitude, where up
tween 10and 20 January1991on the lower slopesof
to eight specieshavebeen observedforagingwith a
Mt. Sumaco(ca. 0ø33'S,77ø44'W),an isolated, forest-
single mixed-speciesflock at at least one site (pers.
obs.).There is, however, a rapid drop-off in the number of speciesof Myrmotherulaoccurringaboveabout
600 m in the foothills of the Andes just a few kilo-
cloakedmountainrisingout of the lowlandsto 3,900
meters to the west. Coincident
with this reduction
in
the number of speciesis a change in speciescompositionwithin the genusas"foothill" speciesreplace
lowland species.Furthermore,the foothill antwrens
occupyan altitudinally compressedrange,being virtually absent above about 1,300 m. Thus, it is not
surprising that some of these birds are among the
most poorly known membersof Myrmotherulaand,
indeed, of the family Formicariidae.
In the next few years, as our taxonomy of birds is
increasinglydeterminedby evidenceof geneticrelatednessthat comesfrom the laboratory,there should
be a correspondingbody of knowledgeavailableon
the behavior
and vocalizations
of birds that will allow
m some 30 km east of the Andes. I observed birds
with Zeiss 10 x 40 binoculars. When I located a mixed-
speciesforagingflock containingMyrmotherula
species
(alwaysfirst detectedby characteristicvocalizations
of one or more flock members),I made representative
taperecordingsof as many differentvocalizationsas
possible,
andfollowedthebirdsfor aslongaspossible
(alwaysat least 20 min, and for as long as 2.5 h),
observingforagingand otherbehaviors,which I summarizedverballyon cassette
tape.All measurements
given below (heights, distances,etc.) are estimates.
Terminologyfor foragingbehavior follows Remsen
and Robinson(1990). Tape recordingswere made us-
ing NagraE, Nagra4.2, and SonyTCM-5000recorders, and Sennheiser MKH-416 and ME-80 shotgun
microphones.All recordings have been or will be
archivedat the Libraryof NaturalSounds,Cornell
University, Ithaca, New York. Sonagramswere producedwith "SoundEdit" of Farallon Computing, Inc.,
senberg1990).Tissuesamplesare fastaccumulating, Emeryville,California,and "Canary"of the Bioacous-
a test of our ability to use data from both fields to
predict evolutionary relationships(Hackett and Ro-
andmolecular-based
phylogenieswill beworkedout,
in many cases,beforepertinentdata from the field
tics ResearchProgramat the Cornell Laboratoryof
are gathered and assimilated.In this paper I provide
Ornithology, Ithaca, New York.
Foothill Antwren (M. spodionota).--Myrmotherula
standardized
spodionota
(includingthe southernsubspecies
sororia)
data on the behavior
and vocalizations
of four little-known Myrmotherulaantwrens from
occurs from northeastern
Ecuador south in a narrow
470
elevational
ShortCommunications
andCommentaries
band
in the foothills
of the eastern
Andes
to Depto. Junln, Peru. I encountered spodionota
from
600 to 1,250 m; it was especially common between
about 700 and 1,100 m. The upper elevational limit
for the speciespreviously has been reported as 1,100
m (Hilty and Brown 1986,Sibley and Monroe 1990).
During a two-week survey in apparently suitablehabitat between 1,000and 1,300 m in Depto. San Martin,
Peru, spodionotawas not found (Parker and Parker
1982), which probably indicates that it is at least locally absent from this elevational range in northern
Peru. Nothing has been published on the behavior
or vocalizationsof spodionota.
I observedthe foraging behavior of 30 to 40 individualsand tape-recordedapproximately10 different
birds. Myrmotherulaspodionota
was almost always observed foraging with mixed-speciesflocks of insectivores in the understory of undisturbed forest. All
foraging took placebetweenabout0.5 and 8 m above
ground, most often between 1 and 4 m aboveground.
Within each mixed-speciesflock, spodionota
occurred
in male-female pairs or occasionallysmall groupsof
up to four individuals in which casethree of the birds
were usually in female/immature plumage, almost
certainly representing a family group. A food-begging juvenile with two adults was observedon 28
March. This juvenile was also foraging indepen-
dently, and wassinginga goodapproximationof the
[Auk, Vol. 111
hopped onto a leaf in the cluster or poked or grasped
it with the bill. Theseactionsprobably serve to startle
any hiding arthropodsinto making noise with even
a slight movement,thus alerting the bird to the presence of a hidden prey item. The birds often spent
several seconds,usually not more than about 1 rain,
rummagingaudibly in clustersof deadleavesas they
reachedinto curls and crevices.I noted that spodionota
scannedlive leaves as it hopped along limbs, but I
saw only a couple of brief lunges (and no prey cap-
tures)in live foliage.By the definitionof Reinsenand
Parker (1984), spodionota
should be considered a deadleaf foraging specialist.
All foraging attackswere near-perch maneuvers.
Reacheswere most common, but gleans also were
employed frequently, and I noted hang maneuvers
on severaloccasions.If a large prey item wascaptured,
the bird held it in the bill as it flew or hopped from
the dead leavesto a nearby horizontal perch and there
mashed the body in the bill and thrashed the head
of the arthropod againstthe substrateforcefully and
rapidly, sometimesfor nearly 1 min. Prey items included a variety of arthropodsranging in size from
small roaches,caterpillars, and adult moths to an orthopteran ("katydid") in excessof 5 cm in length.
Large prey items required several minutes to subdue
and swallow (legs and wings were sometimes removed), a delay that usually resulted in the other
membersof the mixed-species
flockhaving movedoff
adult's song. On two occasionsI noted the presence
of two birds in adult male plumage in a single flock.
Whether this representedan advancedplumage state
in an offspringor the presenceof more than one adult
male (and, thus, presumably more than one pair) in
these flocks could not be determined, but I suspect
the former. The only spodionota
that I observed away
from mixed-speciesflocks were a single adult male
singing shortly before dawn, before formation of
mixed-speciesflocks,and a probablefamily group of
four that did not seemto be associated
with any flock.
While searchingfor food, the birds frequently flicked
the tail up or down sharply through an irregular arc,
by membersof a pair or family group.My approach
to a mixed-species
flockcontainingspodionota
usually
andflickedthe wingsshallowly,especiallyafterland-
stimulated
some distance.The only congenersI found in the
same mixed-speciesflocks with spodionota
were M.
longipennis
(Long-winged Antwren; which foragedat
similar heights but primarily in live foliage), M. behni
(which generally foraged higher and more in live
foliage),and M. menetriesii
(Gray Antwren; which foraged higher above ground and primarily in live foliage).
While foraging, spodionota
was generally quiet except for soft,but sharp,single-notecontactcallsgiven
at least
one bird
to deliver
an alarm
vo-
calizationconsistingof a rapid seriesof high, thin
Myrmotherulaspodionota
foragedalmostexclusively noteslasting about 1 s (Fig. 1A). A distinctive vocalat isolateddeadleavesand dead-leafclustershanging ization in which the notes are at about 3.5 kHz and
or trappedaboveground in the forestunderstory.On delivered much more slowly and with a raspyquality,
several occasionsI noted spodionota
probing in tufts was also given occasionally,mostly after tape playof mossand in the shaggy,dead bark of understory back.This vocalization is often employed in agonistic
vines.The birds approacheda deadleaf or leaf cluster situations,such as flock-territory defense(K. Rosenby flying in to land immediatelybesideit, or by hop- berg pets. comm., M. and P. Islet pers. comm.; Fig.
did not sing
ping or hitching along limbs ("hitching" defined as lB). During Januaryto March, spodionota
ing on a new perch.
a sideways movement of one foot followed immediately by other, producing short advancesof lessthan
about 2 cm [or the distancebetween the legs when
perched normally]). Isolated dead leaves, especially
smaller ones,were scannedfor prey items by stretching the legs, and craning the neck in various positions. Foraging at a cluster of dead leaves or large,
isolateddead leavesusually was initiated as the bird
often except in the early morning (mostly prior to
the formation of mixed-speciesforaging flocks) or
following tape playback.The songis a rapid seriesof
15 to 20 notes at about 5.5 kHz
that is loudest
in the
middle and trailsoff as it dropsslightly in frequency
toward the end, the whole lasting approximately1.0
to 1.5 s (Fig. 1C). In eastern Ecuador,at least, both
sexesof spodionota
have a dark-brown iris.
April1994]
Short
Communications
andCommentaries
Plain-wingedAntwren (M. behni).--Myrmotherula
behniis poorly known throughoutits range, which
8
forms
afragmented
arcaround
thenorthwestern
bor-
6
der of Amazonia.It occursin: the Pantepui region of
southern Guyana, southern Venezuela, and extreme
4
northwestern
Brazil;
theSierradeMacarena
of east-
2
ern Colombia;and the Sumacoregion of easternEcuador, where first recordedby D. Norton in the early
1960s (R. Ridgely pets. comm.). Nothing has been
0
^
0.2
6
thatit occurs
in "forests
andclearings,
fairlylowin
4
0.8
1.0
1.0
2.0
3.0
4.0
=o
was1,200m, although
I conducted
observations
in g 8
continuous,
mostlyundisturbedforestup to 1,750m.
The observedelevationalspreadis well below that
0.6
',r
I foundbehni
to be fairlycommon
(15to 20 indi- • 0
vidualsobserved)
betweenabout780and 1,100m, >,
mostcommonat about1,000m. My highestrecord
0.4
B
publishedon thebehavioror vocalizations
of M. behni
exceptfor the brief statementby Snyder (1966:178)
treesand undergrowth,"and her descriptionof the
voiceas"a mediumhigh trill, 'kyerrrrrrr.'"
471
C
• 6
u_ 4
reported by Hilty and Brown (1986:395;1,300to 1,800
m) and Meyer de Schauenseeand Phelps (1978:210;
2
1,000 to 1,800 m) for Colombia and Venezuela, re-
0
spectively.Although it is possiblethat I missedall
0.5
1.0
1.5
birds above 1,200 m or that localized conditions were
suboptimalfor behniabovethatelevation,it isperhaps
more likely that behnioccursat somewhatlower elevations in the Sumacoregion of Ecuadorthan in
other
known
areas of its distribution.
6
4
Myrmotherula
behniforagedexclusivelywith mixed-
2
species
flocks
in theunderstory
andmidstory
of un-
0
disturbed forest. They seemedto be partial to damp
ravines.Although bamboo(Guaduasp.)was common
in some of the areas in which I found behni, the birds
did not seemto prefer to foragein bamboomore than
in other vegetation.I observedbehniforagingfrom 1
to 10 m aboveground. In areasof the foresthaving
dense(interlockingplants)understory,behniforaged
primarilyin the lowerpartof itsforagingrange.Where
the understorywas open, the birds foragedmore in
the 4- to 10-m range. When in the understory (less
than about 3 m aboveground), behniforagedmore
often in dead leavesthan when foraging in the midstory,probablybecauseof the higher densityof suspendeddeadleavesat lower levelsin the forest.I do
not believe that behnisoughtdead-leafsubstratesover
other substrates,although this was difficult to ascertain. I observedbehniforaging at dead leaves about
half of the time, which would categorizeit as a "regular user" of dead leaves as a foraging substrateby
O.5
Time
1.0
1.5
(seconds)
Fig. 1. (A) High-pitched scold and (B) raspy "alternatesong"given in agonisticcontextof Myrmotherula spodionota
(recordedon Mr. Sumaco,western Napo
Prov., Ecuador).Songsof (C) M. spodionota
(recorded
on Mt. Sumaco,western Napo Prov., Ecuador)and
(D) M. ornata(recorded at Serra dos Carajas,central
Para, Brazil; song sharedby both rufous-backedand
gray-backedpopulations).These vocalizations,with
little interspecific variation, are shared by all membersof checker-throatedgroup (asdefined by Hackett
and Rosenberg[1990],but excluding M. gularis).
and upon reachingthe end of the limb, peeredat the
underside of the leaves,or hung sidewaysor upside-
the definition of Remsen and Parker (1984). However,
down at the tips of leaves,sometimesclinging to the
behnirarely manipulated dead leaves (by tapping, leaf marginswith the feet, and sometimesmaintainprobing,or rummaging),which suggests
a low level ing a hangfor severalsecondsastheycranedthe neck
of specializationin dead-leaf foraging (Rosenberg to scansurroundingfoliage.In general,behniforaged
1993).
actively and acrobatically,reaching and gleaning arSearchesof dead and live foliage were concentrated thropodprey, mostof which were too smalland conat the periphery of trees,where singleor smallclus- sumed too quickly for me to see clearly. The birds
ters of dead leaveshad becometrapped in twigs and also performed short flutter chases,and sometimes
live foliage.The birdshopped or hitched along limbs seemedto be inspectingfoliageby fluttering closeto
472
ShortCommunications
andCommentaries
8
[Auk,Vol. 111
A
6
B
4
2
0
0
8
0.2
0
0.4
1.0
2.0
3.0
4.0
C
6
6
4
4
2
2
i-
t.t_
0
0
0
0.2
0
6
0.5
1.0
1.5
2.0
0.5
1.0
1.5
2.0
F
4
2
,
0
0.2
0
0
Time
(seconds)
Fig. 2. Some calls and songsof Myrmotherulaantwrens recorded on Mt. Sumaco,western Napo Prov.,
Ecuador,presentedfor interspecificcomparison.
Myrmotherula
behni:(A) "dyink!" or "deenk!"call (left), which
seemsto functionasan alarmor heightened-awareness
note,and "kleek" or "wheet"call (right), which seems
to function asa general contactnote. (B) One song.Few songswere heard,so it was not possibleto determine
if thisis a typicalsong.Myrmotherula
sunensis:
(C) "sue•t"or "tue•t" call,whichseemsto bea generalcontact
note. (D) One song.First note soundsslightly more bisyllabicand is slightly higher in frequencythan
subsequentnotes;number of notesvariable from two to five. Myrmotherulaschisticolor
interior:(E) "pseeyt"
call, which seemsto function as a general contactnote. (F) One song. Last note is usually given after a
fractionallylongerintervalthanthosebetweenothernotepairs.Songis muchlike thatof sunensis,
but differs
in being "sharper"in quality owing to loudernotesand suddensyringealclosureat high end of individual
notes.There alsois a somewhatlonger interval betweennotes;number of notesvariablefrom two to four
(fewer than 10 songsheard from two individuals).
it. The birdsalmostconstantlyflicked their wingsand
tails shallowlywhile foraging,more emphaticallyin
response
to tapeplayback.
Congeners
observed
in the
same mixed-speciesflocks with behniwere M. spo-
dionota,M. erythrura (Rufous-tailed Antwren; once,
foraging almost exclusively in dead leavesand more
in the interior of vine tangles), M. axillaris(Whiteflanked Antwren; once, foraging more in live foliage
April 1994]
ShortCommunications
andCommentaries
473
and lessat the peripheryof trees),M. longipennis
(twice,
foraging in live foliage while behniforaged mostly in
dead leaves), and M. menetriesii
(generally foraging
higher above ground).
Upon my initial approach toward a mixed-species
flock,behnisometimesgavea single-notedcall,which
I believe functions as an alarm note or heightened
awarenesscall. I have transcribed it as "dyink!" or
"deenk!" (Fig. 2A, left side). The most common vo-
dant below about 5 m. Several exceptionally diverse
mixed-species flocks of insectivores were encountered in this old secondgrowth, including one flock
in which the following speciesof Myrmotherulawere
calization of behni, however, was a rather loud "kleek"
definitely moving with this flock, which contained
or "wheet" that membersof a pair seemedto use for
keepingin contact,especiallywhen flying from perch
to perch (Fig. 2A, right side). This vocalization was
alsogiven frequently in responseto tape playbackof
any vocalization of behni.I did not hear behnigive
anything similar to the call describedabove by Snyder (1966). I heard the song of behnion only one
no fewer than 42 bird speciesobserved foraging for
arthropods.
Within mixed-speciesflocks,M. sunensis
foragedin
male-female pairs (one pair per flock), ranging from
1 to 7 m aboveground, mostoften betweenabout2.5
and 5 m. The birds foraged rather lethargically, performing gleans and reaches in a deliberate manner
without hanging, sallying, fluttering, or other acrobatic moves. They hopped and hitched along horizontal and diagonal limbs, sometimesclinging momentarily to vertical stems and vines as they
progressedtoward the ends of limbs. Myrmotherula
sunensis
foraged in both live foliage and at isolated,
often small, dead leavesby stopping immediately beside the substratethen stretchingthe legsand craning
the neck and bending over to scanvarious surfaces
for prey items. Myrmotherulasunensis
did not hop directly onto dead leavesand usually did not poke or
probethem with the bill. The birds did not rummage
in deadleaf clusters,but did occasionallyinspectclustersfrom the periphery. If a prey item was found, the
bird rapidly snappedit up and quickly swallowed it,
sometimesafter mashing it in the bill and beating it
on a limb for a few seconds.A majority of my foraging
occasion
in several
hours
of observation.
An
adult
male delivered two or three quiet songsfrom a horizontal perch about 5 m aboveground after playback
of both calls describedabove. The song is a seriesof
five to nine clear, very slightly descending,evenly
spacedwhistled notes at 3.5 to 4.0 kHz lasting 4 to
5 s (Fig. 2B).
Rio SunoAntwren(M. sunensis)--Myrmotherula
sunensisprobably hasthe most restricteddistribution of
any Myrmotherulaoccurringin western Amazonia.It
is known from one localityin southeasternColombia,
a clusterof localitiesin western Napo Province, Ecuador, and two localities in northern and central Peru,
all of which
lie in a narrow
elevational
band between
about 250 and 500 m along the eastern base of the
Andes. Additionally, Stotz (1990) reported a single
male specimenfrom the middle Rio Jurufiin western
Amazonian Brazil, which he distinguished from the
morphologically very similar M. iheringi(Ihering's
Antwren) by its "gray underwing coverts,instead of
pure white." Apart from the equivocal statement of
Hilty and Brown (1986) that its behavior is "apparently much like Long-winged Antwren," sunensis
is
virtually unknown in life.
I observedtwo pairsof sunensis
foragingwith mixedspeciesflocksin the understoryof old second-growth
terra firme rainforest (possibly flooded on occasion)
at approximately400 m. This forestwas regenerating
from essentially clear-cut condition, but had remained undisturbed for long enough to attain an average canopy height of about 20 m, and was directly
connectedto essentially undisturbed forest on the
lower slopesof Mt. Sumaco.Scatteredthrough the
canopy were numerous light gapschoked with vine
tanglesin which the canopy height was lower than
about 8 m. Dense patchesof Guaduasp. bamboowere
present, and another type of bamboowas more generally distributed throughout. Despite the abundance
of bamboo,sunensis
rarely foragedin it, and actually
seemed to prefer other types of vegetation. The understorywas generally denseand viny with abundant
Heliconiaspp., and suspendeddead leaveswere abun-
observedforagingovera periodof about2.5h: brachyura(PygmyAntwren), hauxwelli,ornata,erythrura,axillaris,longipennis,
sunensis,
and menetriesii.
The first two
speciesare not inveterate members of mixed-species
foraging flocks(the others are; pers. obs.), but were
observations of sunensiswere at dead leaves (ca. 40
foraging movesobserved),which would categorizeit
asa dead-leaf-foraging
specialistunderthe definition
of Reinsen and Parker (1984). Rosenberg(1990) defined a specialist,however, as a speciesthat manipulates the substratephysically with the bill or feet,
offering further clarificationin statingthat "non-specialistsvisually inspecteddead leavesbut rarely disturbed the leaves to facilitate prey detection." Based
upon my rather limited observations,I would classify
sunensis
as a nonspecialist,regular user of dead-leaf
foragingsubstrates.
Both membersof a pair foraged
in the same manner, usually keeping within about 5
m of each other. They flicked the tail irregularly and
shallowly, and seemedto flick the wings somewhat
lessoften than do most speciesof Myrmotherula.
Myrmotherulasunensiswas generally quiet while
foraging,but occasionallymembersof a pair called
activelyto eachotherwith single-noted,rising"sue6t"
or "tue6t" callsthat were often delivered in pairs (Fig.
2C), and quieter callson a lower frequencythat were
usually given in a short seriesof three or four notes,
especiallywhen moving quickly or flying between
perches. These calls were also given in responseto
tapeplaybackof thesevocalizationsor the song.None
474
ShortCommunications
andCommentaries
[Auk,Vol. 111
of the callsof sunensis
that I heard were obviously pears to be a dead-leaf foraging specialist, like all
given in the manner of an alarm or scold. One of the
other Myrmotherula species having a "checkered"
malesunensis
thatI observedwassingingoccasionally
while it foragedwith a mixed-species
flockabout2.5
h afterdawn.Thesongisshortandsimple,consisting
of two to five (usuallythree or four) evenly spaced
notesat about 5 kHz that rapidly rise throughabout
1 kHz. The first note is about 0.5 kHz higher in frequency,and is slightly more drawn out (more bisyllabic) than the rest.A five-notesong is about 1.75 s
throat (Remsen and Parker 1984, Gradwohl and
Greenberg 1984, Rosenberg1993) with the exception
(pers.obs.)of M. gularis(Star-throatedAntwren), which
is isolated
in the Atlantic
Forest of southeastern
Bra-
zil, and seems closer to M. guttara (Rufous-bellied
Antwren) and M. hauxwelli(contra the suspicion of
Remsen and Parker 1984). The song of spodionota
clearlyalliesit to the otherchecker-throatedmembers
long (Fig. 2D). I have transcribedit as, "suweee-swee- of the genus, and the closely related (Hackett and
swee-swee-swee."
A female also sangthis songone Rosenberg1990) M. ornata(pers. obs.;compareFig.
time. In the absenceof tape playback,sunensis
deliv1C and 1D). The high-pitched scoldof spodionota
(Fig.
ered songsquietly and at irregular intervals, often 1A) is typical of all true checker-throatedantwrens.
goingfor severalminuteswithoutsinging,thensing- The raspy vocalization given by spodionota
in an aging several songsa few secondsapart.
onistic context (Fig. lB) has been characterizedas "apSlatyAntwren(M. schisticolorinterior).--Although
parently a unique type of alternative song in this
schisticolor
isamongthe mostwidely distributedmem- [checker-throated]group" (K. Rosenbergpers.comm.),
bers of Myrmotherula(occurring from southern Mexalthough it is not known whether all of the members
ico to Depto. Cuzco,Peru), its foraging behaviorand of the group give it. Most of the vocalizations (esmost of its vocalizationsremain poorly known. The pecially the songs)of the checker-throatedgroup are
subspeciesM. s. interior is sympatric with sunensis audibly and structurallydistinctfrom thoseof all oththroughout the range of that species,but the two do er speciesof Myrmotherula(pers. obs.),and the close
not overlap altitudinally (schisticolor
doesnot seemto
vocal similarity found within the group supportsthe
occur below about 1,000 m on the east slope of the
finding of Hackett and Rosenberg(1990) that the
Andes, and is rare that low; pers. obs.).Like sunensis, checker-throated group (including M. ornata) forms
schisticolor
interiorforages with mixed-speciesflocks a clade.
in the understory of forest, ranging from near the
In the allozyme study of Hackett and Rosenberg
ground to as high as about 12 m, most often between (1990), M. behni (sample from Cerro de la Neblina,
about 2 and 6 m above ground. Myrmotherulaschisti- Venezuela) and M. grisea(Ashy Antwren) of the Bocoloralso appears to be a generalist forager and a livian foothills clustered with M. schisticolor
(sample
"regular-user" of dead-leaf foraging substrates.It is of nominate, trans-Andeansubspeciesfrom Darien,
somewhat more acrobatic than sunensis,
performing
Panama).Sucha relationship would be hard to predict
more rapid motions as it reaches,gleans, and hangs from nonmolecular evidence, given the different voin live and dead foliage. On Mt. Sumaco,most mixedcalizations and very different plumages of behniand
speciesflockscontaining schisticolor
contained no othschisticolor.
A close relationship of behnito the other
er speciesof Myrmotherula,but often seemedto have all-gray, plain-winged taxa, griseaand M. unicolor
two pairs of schisticolor,
or at least two adult males (Unicolored Antwren of Atlantic Forest of Brazil) is
and two or three female-plumagedbirds.
suggested,however, by available morphological, beThe mostfrequentlyheardcontactcall of schisticolor havioral, and vocal evidence(pers. obs.)Myrmotherula
interiorwas probably transcribedby Eisenmann (in behniincludes at least three geographicallyisolated
Peterson and Chalif 1973) as "pseeyt" (Fig. 2E). The
populations,and three subspecies,although two of
song of schisticolor
interior(only one bird recorded) is the subspeciesare in Pantepui and the Ecuadorian
a series of two to four notes at about 4 kHz that rise
population is not subspecificallynamed. In light of
rapidly through about 1 kHz and end with an abrupt apparent differences in the morphology, elevational
syringeal closure(Fig. 2F). It may be much like the spreads,and calls of some of these isolates,I suspect
songof nominate schisticoloras
Skutch(1969:210),who
that behnimight include more than one species-level
provided the only description of the species'song, taxon. Tape recordingsof songsand calls and additranscribed it: "t'weet t'weet t'weet, t'weet weet weet
tional tissuesamplesof all of the populations of behni
weet weet, in very low soft tones."The best-known (and similar material from other species)are needed
vocalization of schisticoloris a nasal, descending to clarify its taxonomicrelationships.
"nyeeah" (Petersonand Chalif 1973)or "yyeeet" (HilMyrmotherulasunensis
bears a striking morphologty and Brown 1986).This vocalizationmay be an alarm ical resemblanceto iheringi.The two also forage in a
or heightened-awarenesscall, given by one or more similar, lethargicmanner, often inspectingsmall,isoindividuals as soon as any threat, such as the aplated dead leavestrapped in live vegetation.In southpearance of an observer, is detected. The extent to westernAmazonia,at least,iheringiseemsto be largely
which it is given in the absenceof disturbanceneeds restrictedto bamboothickets(pers.obs.,K. Rosenberg
further investigation.
pers. comm.); the extent to which sunensis
might be
Possiblerelationships.--Myrmotherula
spodionota
aptied to bamboo needs further investigation. Songsof
April 1994]
ShortCommunications
andCommentaries
475
sunensis
and iheringiare quite different in structure, ler, Theodore A. Parker III, J. V. Remsen, Jr., and
frequency,rateof delivery, and overall duration(pers. especiallyKenneth V. Rosenbergfor their helpful
obs.).That thesetwo otherwisecloselysimilar species commentson the manuscript.
should have very different songsfinds parallel, within Myrmotherula,in brachyuraand sclateri(Sclater's
Antwren), which Hackett and Rosenberg(1990)found
LITERATURE CITED
to be quite closelyrelated genetically.
Notwithstanding the observedsimilarities to iher- CHAPMAN,
F.M. 1925. Descriptionsof one new geingi,sunensis
appearsto be mostsimilar overall to schisnus and of species of birds from Peru and Ecticolorin plumage,behavior,and structureand quality
uador. Am. Mus. Novit. 205:1-11.
of the contactnote and especiallythe song. In the
GRADWOHL,J., AND R. GREENBERG.1984. Search be-
type description of sunensis,Chapman (1925) discussedthis relationship based upon observedsimi-
havior of the Checker-throatedAntwren forag-
laritiesi• plumage,and subsequent
taxonomic
lists
281-285.
ing in aerial leaf-litter. Behav.Ecol.Sociobiol.15:
have invariably placed the two closetogether.Com- HACKETT, S. J., AND K. V. ROSENBERG.1990. Comparisonof the songsof sunensis
and schisticolor
interior
parisonof phenotypic and geneticdifferentiation
(Fig. 2D and 2F, respectively)revealsa closesimilarin South American antwrens (Formicariidae).Auk
ity, although the song of schisticolor
interioris gener107:473-489.
ally louder and sounds"sharper" in quality owing to HILTY,S. L., ANDW. L. BROWN.1986. A guide to the
the sudden cut-off at the high end of the individual
birds of Colombia. Princeton Univ. Press, Princenotes.The songsof schisticolor
interiorand sunensis
are
ton, New Jersey.
much more similar
to each other than either
is to the
song of any other speciesin the genus (pers. obs.).
The "sue•t"
contact call of sunensis is much like the
MEYERDESCHAUENSEE,
R., ANDW. H. PHELPS,
JR. 1978.
A guideto the birdsof Venezuela.PrincetonUniv.
Press,Princeton,New Jersey.
common, apparently analogous"pseeyt" call of schis- PARKER,T. g., III, AND S. A. PARKER. 1982. Behavticolor(compare Fig. 2C and 2E). I would not be surioural and distributional
notes on some unusual
prised to learn, eventually, that similar basiccontact
birds of a lower montane cloud forest in Peru.
callsare sharedby many speciesof Myrrnotherula
(and
Bull. Br. Ornithol. Club. 198:63-70.
perhapssomeother thamnophilines).I did not hear PETERSON,
R. T., ANDE.L. CHALIF.1973. A field guide
any vocalization of sunensis
that I thought was analto Mexican birds. Houghton Mifflin Co., Boston,
ogousto the distinctive,nasal"nyeeah"(Petersonand
Massachusetts.
Chalif 1973) of schisticolor.
REMSEN,J. V., JR., AND T. A. PARKERIII. 1984. ArLike behni, schisticolorincludes three named sub-
species(with the name interiorassigned to populations both north
and south of the Rio Marafion
in
northern Peru), which are probably geographically
isolated by either low-elevation gaps or intervening
dry forestsdespitethe range map shown for schisticolorin Hilty and Brown (1986). Elucidation of both
boreal dead-leaf-searchingbirds of the Neotropics. Condor
86:36-41.
REMSEN,J. V., JR., AND S. K. ROBINSON. 1990. A clas-
sificationschemefor foraging behavior of birds
in terrestrialhabitats.Pages144-160inAvian foraging:Theory, methodology,and applications(M.
L. Morrison, C. J. Ralph, J. Verner, and J. R. Jehl,
the intra- and intergenericrelationshipsof schisticolor
Jr., Eds.). Stud. Avian Biol. 13.
will benefit greatly from further fieldwork, especially ROSENBERG,
K.V. 1990. Dead-leafforagingspecialmore recordings of songs.
ization in tropical forestbirds. Ph.D. dissertation,
Becauseof closesimilarity of the adult male plumLouisiana State Univ., Baton Rouge.
ages, sunensis,
schisticolor,
and longipennis
traditionally
ROSENBERG,
K.V. 1993. Diet selection in Amazonian
have been placed together in systematiclists. In the
antwrens: Consequencesof substratespecializaallozyme analysis of Myrmotherula presented by
tion. Auk 110:361-375.
Hackett and Rosenberg (1990), however, schisticolor SIBLEY,C. G., AND B. L. MONROE,JR. 1990. Distriand longipennis
did not clustertogether (sunensis
was
bution and taxonomy of birds of the world. Yale
not availablefor study).Although their plumagesare
Univ. Press, New Haven, Connecticut.
quite similar (but with different distributionof white SKUTCH,A. F. 1969. Life histories of Central Ameron tips of wing coverts), the separate clustering of
ican birds, vol. III. Cooper Ornithol. Soc.,Pacific
schisticolor
and longipennis
is supported by vocal difCoast Avifauna
35.
ferencesat least(pers. obs.).Whether molecular anal- SNYDER,
D. E. 1966. The birds of Guyana. Peabody
ysis eventually confirms the antwren relationships
Museum, Salem, Massachusetts.
suggestedaboveor not, the behavioral and vocal data STOTZ, D. 1990. Corrections and additions to the
presentedhere may be helpful in arriving at a wellBrazilian avifauna. Condor 92:1078-1079.
corroboratedphylogeny for Myrmotherulaand the
family Formicariidae.
Acknowledgments.--Ithank Morton and Phyllis Is-
Received
23 December
1992,accepted
2 July 1993.