210
Short Communications
[Auk, Vol. 100'
Female-FemalePairs and PolygynousAssociationsin a
Quebec Ring-billed Gull Colony
MARIE-CHRISTINE LAGRENADE 1 AND PIERRE MOUSSEAU
Centrederecherches
dcologiques
deMontrdal,Universitd
deMontr•al,5858,
C•te desNeiges,bureau400, Montrdal,QudbecH3C 3J7, Canada
Recently, female-femalepairs have been discovered in severalspeciesof Laridae: WesternGull (Larus occidentalis;Hunt and Hunt 1977), California Gull
(L. californicus;
Conoveret al. 1979),Herring Gull (L.
argentatus;
Fitch1979)and Ring-billedGull (L. delawarensis;Ryder and Somppi 1979, Conover et al.
1979). These pairs usually attend superclutches(i.e.
5-8 eggs).Hunt andHunt (1977),however,havealso
found female associationsattending normal-sized
clutches(1-3 eggs).Mate fidelity and site tenacityin
female-femalepairshavebeenfoundin WesternGulls
(Hunt and Hunt 1977) and in Ring-billed Gulls (Kovacsand Ryder 1981).In view of thesefindings, our
objectivesin thepresentstudywereto determinethe
proportionsof female-femalepairs and of trios, consisting of a male and two females,that were associated with superclutchesand the breeding success,
egg-fertilityrate, site tenacity,and mate fidelity of
birds in these unusual mating systemsat a Ringbilled Gull colonyat Ile de la Couv•e, which is lo-
ite Island(1.9% out of 1,911nests;Ryderand Somppi
1979;P < 0.01)andin Washington(1.3%out of 1,669
nests;Conoveret al. 1979; P < 0.05) but is comparable to that in 21 Herring Gull coloniesof the Great
Lakes (0.3% out of 10,707nests;Shugart1980; P •
0.05). All of theseabovepercentagesare much lower
than those found in the Santa Barbara Western Gull
colony (10-15%, Hunt et al. 1980). In this latter
species,however, contraryto the Ring-billed Gull, a
4-egg clutch is considereda superclutchand is associatedwith female-femalepairs.
Four-egg clutcheswere attended predominantly
(95%) by male-femalepairs (P < 0.001), suggesting
the capacityof thesefemalesto lay four eggsand/or
the occurrenceof egg dumping (Table 1). One female-femalepair was alsocapturedfrom a four-egg
nest. Five-egg clutcheswere attendedequally by
male-femaleor female-femalepairs or one male-two
female associations(P > 0.05). We found that 83%
of six-eggclutcheswere attendedby female-female
cated in the Saint-Lawrence Seaway near Montreal
pairs (P > 0.05).
(45ø28'30"N,73ø30'30'•vV).
This colonyhas been previously described by Lagrenade and Mousseau
The finding of onemale-twofemaletrios attending
superclutch,es
is the secondrecordof a polygynous
(1981a).
and released them. To be sure that all attendants were
associationin the Ring-billed Gull. Conover et al.
(1979) reported the presenceof a male with three
females attending a superclutch.Two of the seven
one male-two female trios had a double-cup nest.
The presenceof double-cup nests has been mentioned only by Shugart(1980)in polygynousHerring
Gull trios and by Southern (1978) in a Ring-billed
Gull pair.
Of the 11 pairs of femalesbanded in 1980, three
caught,eachnestwaswatchedfor periodsof up to
remainedtogetherin 1981.Twoof threenestedwith-
1 h per visit. We opened all unhatchedeggsto determinewhetheror not theywerefertile.Addledeggs
were consideredinfertile.Therefore,the fertility rate
in 3 m of their 1980 territory, while the other pair
moved approximately40 m away from its 1980 territory. Furthermore,two femalesfrom a 1980polygynous associationreturned to the same territory
without the male and formed a female-femalepair..
There is no significant difference between the
number of eggs that disappeared (eaten or stolen)
from nests of male-femalepairs and female-female
pairs.In polygynousassociations,
however,therewas
Nestscontainingsuperclutches
were markedwith
flagsand visited at intervalsof 2-3 days,startingat
the end of the laying period (April) of 1980and 1981.
The attendants of such nests were live-trapped in
walk-in trapsplacedon the nest(Weaverand Kadlec
1970). Using Ryder's (1978a)discriminantfunction
on bill measurements, we sexed and then banded
of the eggs(percentage
of eggslaid thatwerefertile)
is an underestimate.We define the hatching rate as
the percentageof eggs laid that hatched and the
hatchingrate of fertile eggsasthe percentageof fertile eggsthat hatched.All statisticaltestsareWilks's
Chi-square(alsocalledG-test;SokalandRohlf1969).
In the 1980and 1981surveysof the Ile de la Couv•e
colony,superclutches
accounted
for lessthan0.14%
of the total nests(14,331).The percentageof superclutchesin theIle de la Couv•ecolonyis significantly
lower than that in Ring-billed Gull coloniesat Gran-
• Presentaddress:Departmentof RenewableResources,
Macdonald
Campusof McGill University,Ste. Anne-de-Bellevue,
Qu4becH9X
1C0, Canada.
a significantincreasein the percentage
of egg loss.
Two-cup nestshad a higher egg-lossrate (0.36) than
did one-cupnests(0.28) in thesetrios (P > 0.05). The
egg-lossrate of the polygynousassociations
of this
study (0.30) seemssimilar to the one observedfor
female-femalepairsby Ryder andSomppi(1979;0.25).
The hatchingrateof the eggsof female-female
pairs
and polygynoustrios was significantlylower (P <
0.01) than that of ma!e-femalepairs (Table 2). This
was partly due to the lower egg-fertilityrate (P <
January
1983]
ShortCommunications
211
TABLE1. Percentageof occurrenceof the different drasticallyreducedsince1969,the pesticidehypothmatingsystems
foundin superclutches
at the Ring- esis may not be applicableto the Ile de la Couvge
billed Gull colonyof Ile de la Couv•e (Quebec) colony.
during the breeding seasons1980and 1981.
(2) Ryder (1978b) consideredwidowed fertilized
femalesforming bonds as a possibleorigin of feClutch size •
male-femalepairs. Although the low egg fertility of
female-femalepairs doesn't fully support this hy4 eggs
5 eggs 6 eggs
pothesis, our observationof a 1980polygynous trio
Mating system
(n = 19) (n = 21) (n = 6)
becominga female-femalepair in 1981does.For feMale-female
94.74 ***•'
47.62
0.00
male-femalepairs exhibiting mate tenacity, this hyOne malepothesiscould explain the origin, but this behavior
two females
0.00
28.57
16.67
doesnot seemto have adaptive significance,as these
Two females
5.26
23.81
83.33
femaleswould have better breeding successif they
}• n -- total nests.
found a male mate instead of maintaining the bond
•' *** -- significantlydifferent from the occurrence
of other mating
systemsfor the same clutch size at P < 0.001.
for a secondyear.
0.01), but the low hatchingrate of the fertile eggsof
the unusual mating systemssuggeststhat poor parentalattentionand caremay alsohavebeen a factor.
In as much as our egg-fertility rate is an underesti-
(3) Female-female pairs could be an adaptive responseto an excessof females in the colony (Hunt
and Hunt 1977). After removing males from several
Ring-billed Gull colonies, Conover (pers. comm.)
found a higher frequencyof female-femalepairs in
these colonies than in control colonies and in pre-
vious years.Conoveralsodiscoveredthat the breeding population of Ring-billed Gulls in Washington
state is highly skewed. Thus, a female that fails to
find a male mate may associatewith another unmatedfemale.They coulddefenda territory, get ferThree hypotheses
havebeenproposedto explain tilized promiscuouslyby alreadymatedmales,build
the occurrenceof polygynousand female associa- a nest, and share incubation and chick-rearing duties. Such associationsare indispensableif birds are
tions in this normallymonogamous
bird.
(1) Toxic chemicalcomponentssuch as DDT and going to breed, becausesingle-parentgulls in coloraise young (Ryder 1978b).
its metabolitesinduce in male embryosof Western nies cannotsuccessfully
and Californiagullshormonalfeminization,leading Knowing that female-female pairs, in this present
with a
to a suppression
of their breedingbehavior(Fry and study, predominantlyattend superclutches
Toone 1981). Such an explanationcould be the key relativelylow egg-fertilityrate,thatsomeexhibitmate
leads
to abnormalpairs in Great Lakes'Herring Gull col- and sitetenacity,and thatsomearepromiscuous
onieswherethesebirdsarehighlycontaminated
with us to support this third hypothesis.
The infrequency of these unusual mating systems
PCBsand otherorganochlorine
pollutants(Gilmanet
al. 1977). During the breeding seasonof 1979, we suggeststhat the Ring-billed Gull shouldstill be conspecies.As superclutches
have
examinedeggs,chicks,and adultsfor the presence sidereda monogamous
of contaminantsand found that the gulls are rela- been observedin this speciessince1941(Moffitt 1942),
tively free of toxicresidues(Mousseauand Lagren- it is likely that female-femalepairs and polygynous
ade 1980). As the use of DDT in Quebec has been associationshave always existed. Ring-billed Gulls
mate, our data are much like thosereportedby Conover et al. (1979; 67%) and by Ryder and Somppi
(1979;69%). Hunt and Hunt's study(1977)onceagain
standsout, with a very low 14% rate of fertile eggs
in superclutches.
TABLE
2. Fertility,hatching,andegg-loss
ratesof thedifferentmatingsystems
observed
at theRing-billed
Gull colonyof the Ile de la Couv•e(Quebec)duringthe breedingseasons
of 1980and 19812
•
Hatching
rate of
Matingsystem
•
Male-female(n = 117)
One male-two females(n = 36)
Femlae-female(n = 64)
Fertility
Hatching
fertile
Egg-loss
rate•'
rated
eggs
t
ratef
0.85**
0.50
0.56
0.69**
0.33
0.38
** - significantlydifferentfrom corresponding
rate in other matingsystemsat P < 0.01.
n - total eggs,
Number of fertile eggsper eggslaid.
Number of hatchedeggsper eggslald.
Number of hatched eggsper fertile eggs.
Number of disappearedeggsper eggslaid.
0.82
0.67
0.67
0.09
0.31'*
0.09
212
ShortCommunications
are opportunisticin both feedinghabits (Lagrenade LAGRENADE, M.-C.,
and Mousseau 1981b) and habitat selection (Soots
and Landin 1978). Therefore, such birds could have
[Auk, Vol. 100
& P. MOUSSEAU. 1981a.
Re-
production des Go•lands a bec cercl• a l'ile de
la Couv•e, Quebec (Canada). Naturaliste can.
108: 119-130.
highly adaptablemating strategies.The origin of female-femalepairs and polygynoustrios is still unß & -1981b. Alimentation des poussins de Go•lands
• bec cercl• de l'ile de la Couclear,but mate fidelity in theseassociations
seems
to indicate an adaptive responseto an excessof fev•e, Quebec (Canada). Naturaliste can. 108: 131138.
malesin the colony.
We are grateful to Robert Pichet and Alfred La- MOFFITT,J. 1942. A nestingcolonyof Ring-billed
Gulls in California.
Condor 44: 105-107.
grenadefor their field assistanceand to Michael R.
Conover for his helpful review of the manuscript. MOUSSEAU, P., & M.-C. LAGRENADE. 1980. Succbs
This studywas supportedby the Centrede recherde reproduction et contaminantspresents chez
ches•cologiquesde Montrealand the salariesfor field
le Gotland a bec cercl• du sud-ouest du Quebec
assistanceby Summer Canada Projects.
(Canada). Rapp. pr•par• par le Centre de rech.
•col. de Montreal pour le Serv. can.faune, Envir.
LITERATURE CITED
Canada.
CONOVER,M. R., D. E. MIrLER, & G. L. HUNT, JR.
1979. Female-female pairs and other unusual
reproductive associations in Ring-billed and
Californiagulls.Auk 96: 6-9.
FitCH, M. 1979. Monogamyßpolygamy, and female-femalepairs in Herring Gulls. Proc.Colonial Waterbird Group 3: 44-48.
FRY, C. M., & C. K. TOONE. 1981. DDT-induced
feminizationof gull embryos.Science213:922924.
GILMANß A. P., G. A. Fox, D. B. PEAKALLßS. M.
TEEPLE, T. g. CARROLLß& G. T. HAYMES. 1977.
Reproductive parametersand egg contaminant
RYDER,J.P. 1978a. SexingRing-billed Gulls externally. Bird-banding49: 218-222.
1978b. Possibleorigins and adaptive value
of female-femalepairingin gulls.Proc.Colonial
Waterbird Group 2: 138-145.
, & P. L. SOMPPI. 1979. Female-femalepair-
ing in Ring-billed Gulls. Auk 96: 1-5.
SHUGART,
G. W. 1980. Frequencyand distribution
of polygynyin GreatLakesHerringGullsin 1978.
Condor
82: 426-429.
SOKAL,R. R., & F. J. ROHLF. 1969. Biometry. San
Franciscoß Freeman.
SOOTS,R. F., JR., & M. C. LANDIN.
1978. Devel-
opment and managementof avian habitat on
levels of Great Lakes Herring Gulls. J. Wildl.
dredged material islands. U.S. Army Engineer
Mgmt. 41: 458-468.
water ways experiment station. Dredged mateHUNT, G. L., JR., & M. W. HUNT. 1977. Femalerial researchprogram.
female pairing in WesternGulls (LarusoccidenSOUTHERN,
W. E. 1978. Ring-billed Gull pair with
talis) in southern California. Science 196: 1466two nests. Wilson
1467.
ß J. C. WINGFIELDßA. NEWMAN, & D. S. FARNER. 1980.
Sex ratio of Western Gulls on Santa
Barbara Island, California. Auk 97: 473-479.
KovAcs, K. M., & J.P. RYDER. 1981. Nest-site te-
Bull. 90: 299-301.
WEAVER,D. K., & J. A. KADLEC. 1970. A method
for trappingbreedingadultgulls.Bird-banding
41: 28-31.
Received1 February1982, accepted
27 May 1982.
nacity and mate fidelity in female-femalepairs
of Ring-billed Gulls. Auk 98: 625-627.
A Record of the Siberian Flycatcher(Muscicapasibirica) from
Bermuda:an ExtremeExtra-limitalVagrant
DAVID
B. WINGATE
GovernmentAquariumandMuseum,P.O. Box 145, Flatts3, Smith'sParish,Bermuda
On 28 September1980 at 1300I was checkingthe
SomersetLong Bay Nature Reservein Sandy'sParish, Bermudafor migratorybirds when I discovered
a medium-sizedflycatcherfeedingalongthe edgeof
a grassy clearing. First impressions suggested an
Empidonaxflycatcher,but on closerapproachI was
puzzled to observea generallydark plumage with
extensivewhite spottingon theupperpartsand dark
spottingor streakingon the underpartsforming a
partialbreastband. Anotherstrikingfeaturewasthe
largesizeof the eyes,enhancedby white eye rings.
This combinationof charactersgave it the general
appearanceof a juvenal-plumagedEasternBluebird
(Sialiasialis)exceptfor the lack of blue on wings and
tail. The behaviorßhoweverßwasunquestionablythat
of a flycatcher.It perchedconspicuously
on low dead
snagsoverhangingthe clearing,lookedaround in
flycatcherfashion,and made frequentflycatching