Multiple Functions of Courtship Displays in Dabbling Ducks (Anatini)

188
ShortCommunications
RIDGWAY, R.
1887.
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G.B. 1887. Descriptionsof two new subspeciesof titmice from Texas.Auk 4: 28-30.
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[Auk,Vol. 107
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THORNTHWAITE,
C.W. 1941. Atlas of climatictypes
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Received
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Austin, Univ. Texas Press.
Multiple Functionsof Courtship Displays in Dabbling Ducks (Anatini)
FRANK MCKINNEY, LISA GUMINSKI SORENSON,AND MARK HART
BellMuseumof Natural History,andDepartmentof EcologyandBehavioral
Biology,
Universityof Minnesota,Minneapolis,
Minnesota55455USA
wall (A. strepera;Schommer 1977), and American Wi-
The displays of courting ducks have been described,analyzed,andcomparedby ornithologists
and
ethologistsfor a variety of reasons.Earlycomparative
studiesshowedthat stereotypeddisplayscanbe used
geon(A. americana;
Wishart 1983)indicatedthat each
majormaledisplaycanbe placedin only oneof these
three categories.Recent studies of White-cheeked
as taxonomic
Pintail (A. bahamensis)and Chilean Teal, however,
characters
and therefore
behavioral
evi-
dence was used extensively to deduce relationships
within theAnatidae(Lorenz1941,DelacourandMayr
1945, Johnsgard1965). Ethologicalanalysesof the
form, contexts,sequences,and spatial orientation of
duck displayshave been usedto infer motivationof
the performer and signal functionsof individual displays (e.g. Dane and van der Kloot 1964,Weidmann
and Darley 1971, Simmons and Weidmann 1973,
McKinney 1975,Standen1980).Other authorshave
explored how ecological and social factors have influenced the evolution of display repertoires(McKinney 1965a, McKinney et al. 1978) or have used
displaysto testpredictionsfrom sexualconflicttheory
(Anderson1984).In spiteof the diverseobjectivesof
these various lines of research,all depend on the
gathering of accuratedescriptiveinformation on displays.
Most of the displaysperformedby male dabbling
ducks(genusAnas)during socialcourtshiphave distinct orientation componentsthat can be usedto identify the target bird. Movie film analyseshave shown
thatmaledisplaysmaybe categorizedinto threetypes:
(Typea) displaysthat are directedat a specificfemale,
(Typeb) displaysthat are directedat rival males,and
(Type c) displaysthat appearto be directedsimultaneouslyat the female and at another male. Evidence
of manykindsindicatesthatdisplaysaimedat females
functionin pair formation(courtshipdisplays)or pairbond maintenance;
those aimed at other males are
agonisticand function in competition for mates or
mate defense.Film analysesof courtship groups of
Mallard (Anasplatyrhynchos;
Weidmann and Darley
1971),Green-wingedTeal(A. crecca;
McKinney1965b),
ChileanTeal (A. fiavirostris;
Standen1976,1980),Gad-
haveconvincedusthat somefrequentlyuseddisplays
of thesetwo speciescannot be assigneduniquely to
one category.We have found that majordisplaysare
used in bothcourtship (male-female) and agonistic
(male-male)contexts,
andapparentlytheyservemultiple signal functions.We draw attentionto this phenomenonbecauseit hasnot beenreportedpreviously,
and we stressthe need to reexamine Anas signaling
systemswith specialattentionto the orientationcomponentsof displays.
In mostmale-female(type a) displays(e.g. gruntwhistle, bridling, head-up-tail-up; terminology for
displaysfollows Johnsgard1965),the long axisof the
male'sbody is broadsideto the female;in others(facing the female, turn-back-of-head),the male'sbill is
pointeddirectlyat, or away from, the female.Lorenz
(1941) noted that these displays often feature conspicuousplumage,and mostare accompaniedby loud
whistlesor grunting noises.During the grunt-whistle
display,malesdirect a spray of water sideways,alwaysaimed at the targetfemale (von de Wall 1963).
Simmons and Weidmann (1973) showed that similar
directionalbiasis presentalsoin three shakingmovementsthat precedemajor displays.Suchdisplaysare
thought to have evolved as signals that indicate the
male'sinterest in a specificfemale and are designed
to attract that female's attention to the performing
male.
Male-male(typeb) displaysare presumedto serve
threat or appeasementfunctions, and to allow assessmentof potential competitors.In Mallards, billup postures with "rabrab" calls occur when males
approachone another.Threatening with open bill or
chasing often follows. The males face more or less
January
1990]
ShortCommunications
obliquely toward one another, and femalesmay or
may not be present (Weidmann and Darley 1971).
Similar bill-up displaysoccurin other speciesin agonisticcontexts.SubordinatemaleGreen-wingedTeal
performnod-swimmingdisplaysin responseto approach by dominant males during social courtship,
and apparentlythis functionsasan appeasement
signal (Laurie-Ahlbergand McKinney 1979).
A good exampleof a display (type c) that appears
to give simultaneoussignalsto > 1 bird is the down-
up of the Green-wingedTeal.The maleorientsbroadsideto the targetfemale,but the displayis given only
when a rival male is present and very close (McKinney 1965b,1975).Often thereis a "3-bird lineup,"
with the long axesof both males and the female all
parallel. The displaying male is positionedbetween
the rival male and the female. Therefore, the down-
up displayof thisspeciesappearsto signalbothcourtship interest to the female and threat to the rival male
(McKinney and Stolen 1982). Standen (1980) con-
cludedthat the pointingor "greeting"displayof the
Chilean Teal hassimilar dual signalfunctionswhen
performedin the presenceof a female and a rival
male.
The down-up (DU) is by far the most frequent
courtshipdisplayof male White-cheekedPintails.This
displaywasidentifiedby Lorenz(1941)asa head-uptail-up, but reinterpretedas a down-up by von de
Wall (1963) and Kaltenhauser(1971). In captives
breedingin flight pens,we observedthat down-ups
are not only directedat femalesin courtshipcontexts
but also at males in hostile contexts. In both contexts,
the performingbird adoptsa broadsideorientation
to the targetbird, and the displayis often followed
by turning the headand then the whole body to face
toward the target bird. When present,the "facing"
component provides unambiguous confirmation of
the identity of the targetbird. Initially we suspected
that thesemaleswere homosexuallyimprinted birds
(Schutz 1965), but this was ruled out becausethe same
individuals gave this display to females as well as
males; and other behavior made it obvious that fe-
males were being courted, but males were being
threatened.
Similar behavior has been documented (Sorenson
unpubl. data) in a wild population of individually
marked White-cheeked Pintails in 1985-1987 on Paradise Island, New Providence, Bahamas. In 3,894
down-up displays, 39% were directed at females
("courtshipDUs") and 51% at males ("aggressive
DUs").The remaining10%werenot classifiedbecause
the targetbird could not be determinedwith certainty. Closetemporalassociation
of aggressive
DUs with
male-malehostility wasconfirmed:77%of the malemale DUs were precededor followed by other aggressivebehavior(open-billthreats,chases,swim-offs,
or fights).No aggressionwas associated
with any of
the courtshipDUs. Furthermore,18%of the aggressive DUs were performed by rival males when fe-
189
maleswere not in the vicinity or were absentfrom
the pondaltogether.Typically,when rival malesmet,
they exchangedbroadsideDUs and, if one male did
not retreat, they almostalways escalatedaggression.
This suggests
that the DU doesindeed servea threat
signal function.
The displaysof captiveChilean Teal were studied
in detailby Standen(1976),who concludedthat gruntwhistleand bridling displaysare performedwith the
long axisof the male'sbody broadsideto a female in
courtship and pair-bond maintenance contexts. In
flight pen studiesof displayorientationsduring interactionsbetween pairs, Hart (unpubl.) found that
thesedisplaysare alsodirectedat males.In groupsof
5-7 pairs of individually marked birds monitored
during 1986-1988,47%of 253 grunt-whistledisplays
and 44%of 209 bridle displayswere directed(broadside)at males.The remaining displayswere directed
(broadside)at females.Many of the male-male displayswere followed immediatelyby overt hostility,
confirmingthat individual malesperform thesedisplays in both courtshipand threat contexts.
Anas displays are typically highly stereotyped actions,and movie film analysesof captivebirds have
not detected
differences
in the form
of these multi-
purposedisplayswhen they are performed in courtship and agonisticcontexts.Although wild WhitecheekedPintailsmayperformdown-upsto bothmales
and females(with or without the facing component),
the turn is often omitted after hostile DUs given in
male-malecontexts.Down-ups directedat femalesor
malesin a courtingparty contextareusuallyfollowed
by facing. More detailed analysesmay reveal other
subtle differencesin the form of the displayscomparable to those found in the calls and posturesof
gulls and terns (Beer 1975, 1980;Veen 1985) and in
the song-spreaddisplaysof grackles(Wiley 1975).
Displayswith multiple functionsare not likely a
widespread,but previouslyunrecognized,phenomenon in dabbling ducks.Although there have been
few detailed studiesof display orientations,much
attention hasbeen given to the courtshipbehaviorof
Anasducksover many years,and there are very few
indicationsthat male-maleorientationof majorcourtship displaysis a regular phenomenon.Severalauthorshavereportedthat socialcourtshipcanoccurin
groups of males when no female is present (Lorenz
1941,Weldmannand Darley 1971,von de Wall 1965,
McKinney 1975),but generally this is rare and, when
it occurs,it could be triggeredby the presenceof one
or morehomosexual
males.Recently,Kruijtet al. (1982)
reported that male Mallards occasionallydirect courtship displaysat other males,and Bossemaand Roemers (1985:153) describethis for a trio involving 1
femaleand2 malesduringa periodof intenserivalry.
More work on Mallards
is needed to determine
if such
behavior occursregularly. Almost all of the well studied Northern Hemisphere speciesof Anasare strikingly dichromatic, and it should be easy to detect if
190
ShortCommunications
[Auk,Vol. 107
playsßPp. 16-54 in Function and evolution in
behaviour(G. Baerends,C. Beer,and A. Manning,
malesare directingthe samedisplaysto malesaswell
asfemales.On the other hand, many Southern Hemi-
Eds.). Oxfordß Clarendon Press.
spherespecies(suchasthe White-cheekedPintailand
ß 1980. The communicationbehavior of gulls
ChileanTeal)havegreatlyreduceddichromatism,
and
and other seabirds.Pp. 169-205 in Behavior of
it is often difficult to be sureof the sexof targetbirds
marine animalsßvol. 4 (J. BurgerßB. L. Olla, and
in groupsof activelycourtingbirds.Carefulanalyses
L. E. Winn, Eds.). London, Plenum Press.
of films of suchspeciesare needed.
BOSSEMA,
I., & E. ROEMERS.1985. Mating strategy,
If multiple useof majorcourtshipdisplaysdoesnot
including mate choiceßin Mallards. Ardea 73:
occurtypically in Northern HemisphereAnas,its regular
occurrence
in the White-cheeked
Pintail
147-157.
and
ChileanTeal requiresan explanation.We suspectthat
the phenomenonis related to the formation of bigamouspair bonds, long-term relationshipsbetween
individual birds that are possiblein sedentarypop-
DANE,B.,& W. G. VANDERKLOOT.1964. An analysis
of the displayof the Goldeneyeduck (Bucephala
clangula(L.)). Behaviour 22: 282-328.
DELACOUR,
J.,& E. MAYR. 1945. The family Anatidae.
Wilson
ulations, or both. The Chilean Teal and White-cheeked
Pintail form bigamousbondsin captivity (McKinney
and Bruggers1983;McKinney 1985),and bigamywas
documentedin all three yearsof a field study (Sorensonunpubl. data) of wild White-cheekedPintails.
During the formation and maintenanceof bigamous
bonds,intense rivalties develop between individual
malesover particularfemales.Male-maledisplays,as
well as other aggressive
behavior,occurfrequently
as males try to dominate one another. In sedentary
populationsß
the sameindividualsmay interactwith
one anotheryear-roundand yearafter year,and complex dominance relationships may develop. Many
populationsof tropicalandSouthernHemisphereAnas
species(including White-cheekedPintail and Chilean Teal) are nonmigratory.
At this stagewe cannotexplainthe causalrelationshipsbetweenmultipurposedisplaysand thesefactors. It is also'possiblethat the multiple use of such
widely distributeddisplaysasthe grunt-whistle,bridling, anddown-upis the ancestralconditionin Anas.
Bull. 57: 3-55.
JOHNSGARD,
P.A.
1965. Handbook of waterfowl be-
havior. Ithaca, Cornell Univ. Press.
KALTENHAUSER,
D. 1971.OberEvolutionsvorg•inge
in der Schwimmentenbalz.Z. Tierpsychol.29:
481-540.
KRmJT,J.P., I. BOSSEMA,
&: G. J. LAMMERS.1982. Effects of early experience and male activity on
mate choicein Mallard females (Anasplatyrhynchos).Behaviour 80: 32-43.
LAURIE-AHLBERG,C. C., & F. McKINNEY.
1979. The
nod-swim display of male Green-winged Teal
(Anas crecca).Anim. Behav. 27: 165-172.
LORENZ,
K. 1941. VergleichendeBewegungsstudien
an Anatiden.J. Ornithol. 89: Erg. Bd. 3: 194-294.
McKINNE¾,F. 1965a. The spring behavior of wild
Steller
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in behaviour
New analysesof displayrepertoiresthat pay special
(G. Baerends,C. Beer, and A. Manning, Eds.).
attention to the orientation componentsof displays
and the long-term relationshipsof the individuals
Oxford, Clarendon Press.
involved are needed to addressthese questions.
These studies were supported by grants to Mc-
Kinney from the National ScienceFoundation(BNS8317187) and the Graduate SchoolßUniversity of
Minnesota. Grants from the Bell Museum's Dayton
NaturalHistoryFundandWilkieNaturalHistoryFund
supportedthe studiesby Sorensonand Hart. We are
grateful to Jeff Burns, Kim Cheng, Dave Bruggers,
and Gwen Brewerfor help with the observations,and
to Gwen Brewerß Sue Evarts, and Mike Sorenson for
comments on the manuscript.
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nual cycle. Ph.D. dissertation,Univ. Manitoba.
Received
16 December
1988,accepted
26 July1989.
TaxonomicStatusof the CoquetteHummingbird of Guerrero,Mexico
RICHARD C. BANKS
Biological
SurveyGroup,NERC, U.S. Fishand WildlifeService,
NationalMuseumof NaturalHistory,Washington,
D.C. 20560USA
An isolatedpopulationof small hummingbirdsin
the stateof Guerrero,Mexico,was originally named
asa subspecies
(brachylopha)
of the much more southerly Lophornis
delattrei,the Rufous-crestedCoquette
(Moore 1949).The form wasnot reportedagainuntil
rediscoveredby Ornelas (1987) and remains known
nothing of significancewasaddedto our knowledge
of it until Ornelas (1987) collected three additional
specimens,one male and two females,in 1986. These
specimens
were takenin mistnetsin evergreensubtropicalforestat Arroyo Grande,13 km northeastof
Paraiso, Guerrero, at an elevation
of 1,350 meters.
by only three male and two female specimens.Ex- Paraiso is in south-central Guerrero, northwest of
aminationof two of the malesindicatesthat the pop- Acapulcoand near Atoyac de Alvarez, and thus ca.
ulationdeserves
specificstatusasLophornis
brachylopha 10 km northeastof the type locality(J.F. Ornelasin
Moore, for which I proposethe EnglishnameShort- litt.).
crested Coquette.
Shortlyafter the reportedrediscoveryof brachyloMoore (1949) basedhis descriptionof brachylopha pha,I studiedMoore's(1949) descriptionof the taxon
on two male specimensfrom San Vicente de Benitez, relative to specimensof Lophornis
delattreidelattreiand
altitude 1,500 ft (450 m) in the Sierra Madre del Sur
L.d.lessoniin
theNationalMuseumof NaturalHistory
approximately70 km northwest of Acapulco,Guer- (USNM). It was readily apparentthat the birds derero. This wasan extensionof the rangeof the species scribed were different--so different, in fact, that I
delattrei,and of the genusLophornis
as then consti- wonderedif they were actually the samespecies.It
tuted, of ca. 1,900 km north from central Costa Rica.
struck me that the stated differences were much like
The subspecies
wasacceptedby Friedmann,Griscom,
and Moore (1950), and the specieswas included in
subsequentguidesto Mexican birds (Blake 1953,Da-
thoseone would recordif specimensof Lophornis
ornataof northeasternSouthAmericawere compared
with delattrei.Subsequently,I examinedtwo of the
three male specimensof brachylopha
(MLZ 46069,
vis 1972, Edwards 1972, Peterson and Chalif 1973).
The descriptionsin most of these guides, however,
were apparentlybasedon other populationsof the
species,as they largely ignored the distinctive characters ascribed to brachylopha
by Moore (1949). This
is especially true of the descriptionsof the then un-
UNAM P007047)and comparedone or both of them
with specimensof all speciesin the genus in the
USNM, the American Museum of Natural History,
and the Museum of ComparativeZoology. The diagnosticcharactersof malesof L. brachylopha,
emphasizedby Hardy and Webber(1975),are the shortcrest,
black bill, terminal tail pattern, and pale abdomen.
Neither of the femaleswas available for study, but
Ornelas(1987) noted that they have the "throat completely white," which distinguishesthem from L. de-
known female!The Mexicanrangeof the specieswas
also noted by Eisenmann(1955), and the distinction
of the form wasaffirmedby Hardy andWebber(1975).
Despite this, the American Ornithologists' Union
(1983)omittedany part of Mexicofrom the rangeof
the species--presumablya lapserather than a denial lattrei.
of Moore's description.
The rufous crest feathers of brachylopha
are wide
After Moore's (1949) description of brachylopha, and short (ca. 1 cm). The feathers on these two spec-