The Auk 115(2):526-528, 1998 FemaleAd•lie PenguinsAcquireNest Material from ExtrapairMales after Engaging in Extrapair Copulations E M. HUNTER •'3 AND L. S. DAVIS 2 •Department ofZoology, DowningStreet,University of Cambridge, Cambridge CB23EJ,UnitedKingdom; and 2Department of Zoology,Universityof Otago,P.O.Box56, Dunedin,NewZealand Femalesof a numberof bird speciesoccasionally November(Spurr 1975b).Our study site is situated havebeenrecordedexchanging copulations directly in the NorthernRookeryat Cape Bird, RossIsland, for food or for accessto food resources(Lack 1940, Antarctica(77ø13'S,166ø28'E).Observations of copBrown 1967). For example, Wolf (1975) found that ulationbehaviorweremadeduringtheprelayingpemale Purple-throatedCaribs(Eulampis jugularis)de- riods in 1993,1994,1996,and 1997.Full descriptions fend groupsof flowersfrom conspecifics but allow of thestudysiteandmethodsare availablein Hunter femalesaccess in exchangefor copulations. Similarly, et al. (1995, 1996). in monogamousRed-billed Gulls (Larusnovaehollan- The followingaccountis basedon 10observations diae),Taskerand Mills (1981)showedthat a femaleis more likely to copulateif the male givesher food involving at leastfive different females,seenover the four seasonsof study.In eachcase,a femalejoined a duringcourtship. Weareunawareof anydescription single,unpairedmaleat hisnestsite;courtship(sideof copulationsbeingdirectlyexchangedfor anyma- ways-stareand bow; Spurr 1975a)was followed by terial item other than food. Furthermore, this behavthe femalelying prone at the male'ssite.The male ior seemsto be limited in monogamousspeciesto then mounted and copulatedwith the female (see within-pair interactions,with no recordsof females Hunter et al. [1995, 1996] for a full descriptionof of any speciestrading food or any other immediate copulationbehavior).In 8 of the 10 casesobserved, material benefit for extrapair copulations(EPCs; copulation resulted in successfulinsemination of an Birkheadand Moller 1992). ejaculate,determined by observationof the male's Here, we describefemaleAd61iePenguins(Pygos- ejaculateenteringthe female'scloaca.In one unsuccelisadeliae)acquiringnest material from extrapair cessfulcopulationattempt, the male producedan malesafter engagingin copulationswith them.This ejaculatethat missedthe female'scloaca.In the rematerial is in the form of small stones used to create maining copulationattempt,the pair wasdisrupted a platformon whichthe femalelaysher two eggs. by a neighboringindividual prior to cloacalcontact, Stonesare in greatdemandin the colonyandarecol- andthemaleterminatedtheattempt.Followingeach lectedby bothmalesandfemalesfromthe groundin copulation,the male dismountedfrom the female, the area surroundingthe breedinggroup (Sladen and shepickedup a stonefrom his nestsiteand left 1958).In addition, individuals regularly stealstones immediately.In 5 of the 10 cases,the femalereturned from thenestsitesof otherindividuals(Sladen1958). to the extrapair male forthwith to take a second Any individual approachinga male at his nest site stoneandleft againwithoutcopulating.Oneof these and taking a stoneis met with an aggressivere- femalesreturned a total of 10 times, taking a stone sponsefrom the site-holder(Spurr1975a).Site-hold- from the extrapairmaleon eachoccasion. At no time ers will peck, "flipper-bash,"and chasestone-steal- was there any aggressive responseby the male;he ers.The benefitof collectingand defendinga large madeno moveto stopthe femalefromtakinga stone pile of stonesis realized under particular weather from his site. Sevenof the 10 femalesthat gained conditions,usually in springtime,when meltwater stonesfollowing copulationswere unbanded,sugcaninundatethebreedingcolony.Floodingby melt- gestingthattheycamefromoutsidethestudygroup water canresultin nestdesertionand eggloss(Tay- in which most of the birds were banded. This was lor 1962).Morenoet al. (1995)foundthat in the close- supportedby the fact that on four occasions,these ly related ChinstrapPenguin(Pygoscelis antarctica), femaleswere followed after copulationand were which displayssimilarstone-collecting behaviorto found to have partnersand nest sitesin breeding the Ad61iePenguin,largenestswerelesslikelythan groupsadjacentto thestudygroup.Eachof thesefesmallneststo fail asa resultof floodingby meltwa- malesreturnedto her partnerimmediatelyafter the ter. Moreno et al. (1995) concluded that stone colEPC and depositedthe stoneat their nest site. The lectingand nestmaintenance improvednestquality remainingthreefemales,eachof whichwasbanded, and increasedreproductivesuccess. copulated and took stones from males within the Ad61iePenguinsare monogamousand breed in studygroupandthenreturnedto theirpartners,also large coloniesin Antarctica.They engagein court- in the study group.Despitea numberof malesen- shipand copulation behaviorduringthe prelaying gagingin EPCsat females'nest sites,in n,ocasedid period,whichspansfrom mid-Octoberto the end of a maletakea stonefrom a female'ssitefollowingan EPC. E-mail: [email protected] In addition, as previouslyreported by Derksen 526 April 1998] ShortCommunications 527 (1975),femaleswere observedacquiringstonesfrom if the male is unaware maleswithoutengagingin copulations. In eachcase, this behaviorwasinitiatedby the femalejoiningan unpairedmale at his site and engaginghim in mutual courtshipbehavior.Shethensimplytooka stone and left the site.Again, the malewasnot aggressive toward the female, suggestingthat females may avoidaggression by solicitingcourtship.Tenfemales wereobservedto engagein thisbehavior:onefemale pairedindividual,he mayview thecopulationasthe initiationof a long-termpartnership, in whichthefemale rearrangingneststones(althoughnot taking them awayfrom the nestsite)would constitutenormal behavior.Because manylong-termpairingsare was observedto take at least62 stonesfrom a single male over a period of approximatelyone hour; another female took one stone from one male and three stonesfrom anothermale four dayslater;a third femaletookstonesfrom a singlemaleon two separate occasions (fourdaysapart).Theincidenceof thisbehavior would have been underestimated because it was recordedlate in the 1996seasonby FMH only, andin 1997.In addition,thisbehaviormayhavebeen overlookedduring periodsof peak copulationactivity becausethe focusof observations wascopulation behaviorrather than courtshipbehavior.In these cases, it wouldappearthatthemalewascheatedinto allowingthe femaleto take a stonewithout gaining anythinghimself. On a few occasions(n = 7), in responseto a female attemptingto steala stonefrom a male'snestsite,the male, insteadof defendinghis stones,attemptedto mount the female. In each of these cases, the female immediatelymovedawayfrom the maleanddid not allowhim to mount.In onlythreeof thesevencases did the femaleleavewith a stone.It is possiblethat the male misinterpretedthe female'shead-down postureduringthe processof choosinga stoneand took it to be the head-bowcourtshipdisplaythat of the female's status as a initiatedby a femalecomingto a male'ssite,courting with him and engagingin copulation,any male ignoringsucha solicitation, or actingaggressively toward a femalemanipulatinghis stones,might miss a genuineopportunityto form a pair. It is harder to seewhat a femalewould gain from tradingan EPCfor oneor two stones.A straightexchangewould suggestthat to the female,eitherthe two wereequallyvaluable,or theEPCwaslessvaluable.This seemsunlikelywhen an EPC hasthe potentialto alterthepaternityof heroffspring,whereas a singlestonedoeslittle to increasethe likelihoodof a successful breedingattempt.It is possiblethat the exchange of oneEPCopensthe way to the femaleto collectmultiplestones,whichmightindeedincrease thechances of heroffspringsurviving.If so,thepair malemightbe predictedto respondto hisfemaleengagingin extrapaircopulations by attemptingto collect enoughstonesto preventhis femalefrom needing to stealthem.Alternatively,a femalemayengage in an EPC for someotherreason(e.g.fertility assurance,increasingthe qualityof her offspring,gaining a potentialfuture partner;Westneatet al. 1990)but then exploit the male'sloweredguard by taking a stoneafter shehas engagedin the EPC. In this scenario,the femalegainsboth an EPCand someeasily obtainednest material. In addition, by returning to usuallyprecedescopulation,althoughin no casedid the femalelie proneat the site,a necessary precursor her pair male with a stone,shemay be supplying him with a reasonfor her absence.This trickery to successfulmounting. It appearsthat femaleAd•lie Penguinswill some- wouldbenefitboththefemaleandtheextrapairmale times acquirenest stonesfrom extrapair malesafter if it reducedthe chancesof the pair maleattempting engagingin EPCs.Variouspoints of interestcan be a retaliatorycopulation(Birkheadand Mailer 1992). noted from theseobservations:(1) femaleschoseunIn conclusion, it appearsthat femaleAd•lie Penpairedmaleswith whomto engagein EPCs(females guins sometimesacquirenest material from extraof mostspecieschoosepairedmales;McKinneyet al. pair malesafter engagingin an extrapair copulation, 1984,Birkheadand Mailer 1992);(2) a high propor- and that both femaleand extrapairmale gain from tion of the EPC attemptswas successful (compared this behavior.Even the female'spair male gains a with 59%,n = 35 pairs,of pair copulations success- stonein his nest,althoughthis particularstoneand ful; Hunteret al. 1995);(3) thecurrencyinvolvedwas the othersin his nestultimatelymay help to protect nest materialratherthan food;and (4) the material the life of an offspringthat is not his own. benefitwasgainedfollowingEPCsratherthan pair Acknowledgments.--We arevery gratefulto Antarccopulations. tica New Zealand for providingexcellentlogistical The male clearlybenefitsby gainingan EPC that Wewouldlike to thank couldresultin offspringfatheredby him but raised supportin all fieldseasons. Corey Bradshaw, Rob Harcourt, Sue Heath, Gary by anothermale(McKinneyet al. 1984,Birkheadand Mailer 1992).The costof one or two stoneswould Miller, Cristian PerezMufioz, and Marj Wright for field assistance and Tim Birkhead and Nick Davies appear to be a small price to pay for so large a potential benefit.The male alsomay gain if allowing a for helpful commentson the manuscript.The refemaleto take a stonemeansthat sheis morelikely searchwas fundedby the Natural EnvironmentReto returnfor additionalcopulations, whichcouldin- searchCouncil,UK (FMH), and the University of creasehischances of fertilizinghereggs.In addition, Otago,New Zealand (LSD). 528 ShortCommunications LITERATURE CITED [Auk, Vol. 115 strapPenguin(Pygoscelis antarctica)1. Sexroles and effectson fitness.Polar Biology 15:533-540. BIRKHEAD,t. R., AND A. P. MOLLER.1992. Sperm SLADEN, W. J. L. 1958.The pygoscelidpenguins.II. competitionin birds: Causesand consequences. The Ad•lie Penguin.Falkland Islands DepenAcademic Press, London. BROWN,R. G. B. 1967. Courtship behavior in the LesserBlack-backedGull, Larusfuscus.Behav- denciesSurveyScientificReports17:23-97. SPURR,E. B. 1975a. Communication in the Ad•lie Penguin.Pages449-501 in The biologyof penguins(B. Stonehouse, Ed.). Macmillan,London. DERKSEN, D. V. 1975. Unreportedmethod of stone SPURR, E. B. 1975b.Breedingof the Ad•lie Penguin collectingby the Ad•lie Penguin. Notornis 22: Pygoscelis adeliaeat Cape Bird. Ibis 117:324-338. 77-78. iour 29:122-153. HUNTER, E M., L. S. DAVIS, AND G. D. MILLER. 1996. Sperm transfer in the Ad61iePenguin. Condor 98:410-413. HUNTER, E M., G. D. MILLER, AND L. S. DAVIS. 1995. Mate switchingand copulationbehaviourin the Ad61iePenguin.Behaviour132:691-707. LACK,D. 1940. Courtshipfeeding in birds. Auk 57: 169-178. MCKINNEY, E, K. M. CHENG, AND D. J. BRUGGERS. TASKER,C. R., AND J. g. MILLS. 1981. A functional analysisof courtshipfeedingin the Red-billed Gull (Larus novaehollandiae). Behaviour 77:222241. TAYLOR, R. I7I. 1962.The Ad•lie PenguinPygoscelis adeliaeat Cape Royds. Ibis 104:176-204. WESTNEAT, D. E, P. W. SHERMAN, AND M. L. MORTON. 1990. The ecology and evolutionof extrapair copulationsin birds. Current Ornithology 7: 331-369. 1984.Spermcompetitionin apparentlymonogamousbirds. Pages523-545 in Sperm competi- WOLF,L. L. 1975."Prostitution"behaviorin a tropical hummingbird.Condor 77:140-144. tion and theevolutionof animalmatingsystems (R. L. Smith, Ed.). AcademicPress,New York. MORENO, J., J. BUSTAMANTE,AND J. VII(IUELA. 1995. Nest maintenance and stone theft in the Chin- Received 26 February1997,accepted 17 October1997. AssociateEditor: J. Ekman TheAuk 115(2):528-532,1998 "Wife-sharing" in the TasmanianNative Hen (Gallinula mortierii): Is it Caused by a Male-biased Sex Ratio? ANNE W. GOLDIZEN?3 ALAN R. GOLDIZEN,• DAVID A. PUTLAND,• DAVID M. LAMBERT?CRAIG D. MILLAR,2 AND JASONC. BUCHAN• •Department of Zoology,Universityof Queensland, Brisbane, Queensland 4072,Australia;and 2Department of Ecology, MasseyUniversity,Palmerston North,NewZealand In many cooperativelybreeding speciesof birds, adult males are thoughtto outnumberadult females (e.g. Red-cockadedWoodpecker[Picoidesborealis], Gowaty and Lennartz 1985; Splendid Fairy-Wren [Malurussplendens], Rowley and Russell 1990;Pied Kingfisher[Cerylerudis],Reyer1990;seeEmlen1984, 1972,Emlen1984,Curry and Grant 1989,Reyer1990, Davies 1992). A shortage of females might result Brown 1987). The occurrenceof male-biased sex ra- (Pruett-Jonesand Lewis 1990). tios in somepopulationsof specieswith helpers-atthe-nesthas led to the hypothesis(the differential mortality model of Emlen et al. [1986]) that a shortage of femalescouldexplain--at leastin part--delayeddispersal,helpingbehavior,andmate-sharing by males(Rowley1965,Maynard Smith and Ridpath A classicexample in the debate on the link betweensexratiosand cooperativebreedingis the Tasmanian Native Hen (Gallinula mortierii). Ridpath (1972b)reportedmale-biasedsexratiosamongboth adults(1.5 malesper female)and chicks(2.8 males per female)in his study population,and an overall sex ratio of 1.22 malesper femaleamong489 indi- from a higher rate of mortality comparedwith males, perhaps associatedwith female-biaseddispersal.An experimentaltest on SuperbFairy-Wrens (Maluruscyaneus) provided support for this model vidualscollectednearhis study area and sexedby E-mail: [email protected]. au dissection.Maynard Smith and Ridpath (1972)used
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