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528 ShortCommunications [Auk, Vol. 115 LITERATURE CITED strap Penguin(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 Depen- Academic Press, London. denciesSurvey Scientific Reports 17:23-97. BROWN,R. G. B. 1967. Courtship behavior in the SPURR,E. B. 1975a. Communication in the Ad•lie Lesser Black-backedGull, Larusfuscus. Behav- Penguin.Pages 449-501 in The biology of pen- iour 29:122-153. guins (B. Stonehouse,Ed.). Macmillan,London. DERKSEN,D. V. 1975. Unreportedmethod of stone SPURR,E. B. 1975b.Breeding of the Ad•lie Penguin collectingby the Ad•lie Penguin. Notornis 22: Pygoscelisadeliae at Cape Bird. Ibis 117:324-338. 77-78. TASKER,C. R., AND J. g. MILLS. 1981. A functional HUNTER, E M., L. S. DAVIS, AND G. D. MILLER. 1996. analysisof courtshipfeeding in the Red-billed Sperm transfer in the Ad61iePenguin. Condor 98:410-413. Gull (Larus novaehollandiae).Behaviour 77:222- 241. HUNTER, E M., G. D. MILLER, AND L. S. DAVIS. 1995. Mate switchingand copulationbehaviour in the TAYLOR,R. I7I. 1962. The Ad•lie PenguinPygoscelis Ad61iePenguin. Behaviour 132:691-707. adeliaeat Cape Royds. Ibis 104:176-204. LACK,D. 1940. Courtship feeding in birds. Auk 57: WESTNEAT, D. E, P. W. SHERMAN, AND M. L. MORTON. 169-178. 1990. The ecology and evolution of extrapair MCKINNEY, E, K. M. CHENG, AND D. J. BRUGGERS. copulationsin birds. Current Ornithology 7: 1984.Sperm competition in apparentlymonog- 331-369. amousbirds. Pages523-545 in Sperm competi- WOLF,L. L. 1975."Prostitution" behavior in a trop- tion and the evolutionof animalmating systems ical hummingbird. Condor 77:140-144. (R. L. Smith, Ed.). AcademicPress, New York. MORENO, J., J. BUSTAMANTE,AND J. VII(IUELA. 1995. Received26 February1997, accepted17 October1997. Nest maintenance and stone theft in the Chin- 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• •Departmentof Zoology,University of Queensland,Brisbane, Queensland 4072, Australia;and 2Departmentof Ecology,Massey University, Palmerston North, New Zealand In many cooperativelybreeding speciesof birds, 1972,Emlen 1984,Curry and Grant 1989,Reyer 1990, adult males are thoughtto outnumberadult females Davies 1992). A shortage of females might result (e.g. Red-cockadedWoodpecker [Picoides borealis], from a higher rate of mortality comparedwith Gowaty and Lennartz 1985; Splendid Fairy-Wren males, perhaps associatedwith female-biaseddis- [Malurussplendens], Rowley and Russell 1990; Pied persal.An experimentaltest on SuperbFairy-Wrens Kingfisher[Ceryle rudis], Reyer 1990; see Emlen 1984, (Maluruscyaneus) provided support for this model Brown 1987). The occurrence of male-biased sex ra- (Pruett-Jonesand Lewis 1990). tios in somepopulations of specieswith helpers-at- A classicexample in the debate on the link be- the-nesthas led to the hypothesis(the differential tween sexratios and cooperativebreeding is the Tas- mortality model of Emlen et al. [1986]) that a short- manian Native Hen (Gallinula mortierii). Ridpath age of femalescould explain--at least in part--de- (1972b)reported male-biased sex ratios among both layed dispersal,helping behavior, and mate-sharing adults (1.5 malesper female)and chicks(2.8 males by males(Rowley 1965,Maynard Smith and Ridpath per female)in his study population,and an overall sex ratio of 1.22 malesper female among489 indi- vidualscollected near his study area and sexedby E-mail: [email protected] dissection.Maynard Smith and Ridpath (1972) used April 1998] ShortCommunications 529 this evidenceto proposethat a male-biasedsex ratio young were banded between six weeks and three setsthe stagefor the occurrenceof "wife-sharing"in months of age; immigrants were banded as soon as this speciesby causinga shortageof availablebreed- possibleafter their establishmentin the study pop- ing females.This casehas been cited in reviewsas an ulation. In total, 371 birds were banded at Maria Is- examplewhere male-biasedsex ratiosmay lead to land. We found no evidencefor a sexbias in capture mate-sharingby males(e.g. Oring 1986,Emlen et al. probability.Of the 11 birds that we failed to catchat 1986,Emlen 1991).Here, we presentdata on sexra- Maria Islandin 1990,8 that we capturedsubsequent- tios and mating patterns from two populationsof ly includedfour malesand four females. TasmanianNative Hens to challengethe assumption The sex of Tasmanian Native Hens cannot be dis- that cooperativebreeding in this speciesoccurs as a tinguished by external characteristics.Ridpath result of a male-biased sex ratio. (1972b) determined the sex of individuals either by TasmanianNative Hens are flightlessrails endem- behavior,which is reliableonly for someindividuals, ic to Tasmania that live in areas with a combination or by dissection.We determined the sex of 74 indi- of open pasture, dense vegetative cover, and water. viduals from the Geevestonpopulation by laparos- TasmanianNative Hens live in groupsof 2 to 17 in- copyor dissection.At Maria Island,we assignedthe dividuals that defend territories year-round(Rid- sexof 231 of the 371 capturedbirds by laparoscopy, path 1972b).Their mating systemincludes frequent 118 by genetic means, and 12 using other criteria mate-sharingby both sexes,at leastin somepopu- (e.g. copulation positions). Sex could not be deter- lations (Goldizen et al. 1998). Tasmanian Native mined for 10 of the banded birds. Hens exhibit monogamy(a singlemale mated to a Sexdetermination by laparoscopyinvolved the di- singlefemale), cooperative polyandry (two or more rect examinationof gonadsusing the proceduresde- males mated to a single female),polygyny (two or scribedin Gibbset al. (1994).The surgicalprocedure more femalesmated to a singlemale), and polygyn- had no observablenegative effects on the birds; all andry (two or more males and two or more females 231 individuals that underwent surgeryat Maria Is- all breeding together). In groups with multiple land were alive and well at least one week after sur- breedingfemales, the femaleslay eggsin communal gery. We did not resight all of the birds that under- clutches.In groupswith multiplebreeding males, all went surgeryat Geeveston,but we believethat this suchmales copulate with the female(s)and then as- was due to a high level of socialinstability in that sistwith all aspectsof parentalcare (Ridpath 1972a, population(Goldizen et al. 1993).Sex determination b, Gibbset al. 1994).Mate-sharing in TasmanianNa- by laparoscopyalso was extremely accurate; no bird tive Hens is more commonamong males than among sexedby this method was observedbehaving in a femalesand usually involvesclosely related males manner contradictory to its assigned sex. We used (Ridpath 1972b).Helping behavioralso is exhibited two different methodsfor the geneticdetermination by somenonbreeding one- and two-year-oldsof both of sex.The first employedtechniques similar to those sexesthat remain in their natal groups (Ridpath given in Millar et al. (1996),with the followingmod- 1972a,b, Gibbset al. 1994),but suchhelping behav- ification:Because only a single female-specificDNA ior usually is minor relative to that provided by fragment was detectedin TasmanianNative Hens, a breeding adults (Goldizen and Goldizen unpubl. control gene,beta-actin, subsequently was hybrid- data). ized to ensurethe presenceof sufficienthigh-quality We studied our first TasmanianNative lien pop- DNA in those individuals assignedas males. The ulation in cattle pasturesnear Geeveston,in southern techniquesused in the secondmethod are described Tasmania,Australia (43ø10'S,146ø55'E), from De- by Griffiths (unpubl.data). Copulationposition was cember1988 to December1989 (Goldizen et al. 1993). usedto determinesex only if the bird was seencop- Our secondstudy populationinhabited an area of ulating more than once. clearedpasture surrounded by eucalyptwoodland We monitoredthe compositionsof most of the Ma- at the northern end of Maria Island off the eastern ria Island groupsdaily through eachbreeding sea- coast of Tasmania (42ø35'S, 148ø04'E). We studied son. Data on the frequenciesof the different mating this population through the consecutivebreeding patterns(monogamy, polyandry, polygyny, polygyn- seasonsof Septemberto December,1990 to 1996.We andry)refer to themating pattern of eachgroup each observedthe populationcontinuously through each year (group-year),either at the time when the group of thesebreeding seasons. laid its first clutchof eggsor at the beginningof No- Birds were trapped,banded with numberedmetal vember(the middle of the breedingseason), which- bands and unique combinations of color bands, ever came first. The criteria used to determine which weighed,measured, and aged;blood sampleswere birds were breedersare presentedin Goldizen et al. collectedas describedby Gibbset al. (1994).A total (1998).We compileddata on adult sexratios from the of 83 nativehens was banded in the Geevestonpop- informationon the membershipsof all groupspres- ulation. At Maria Island, 135 of 146 birds present in ent in this populationeach year at the beginningof the populationwere trapped and banded between November. Adults included all individuals that December 1989 and August 1990. After that, all hatchedin the previousbreeding season or earlier 530 Short Communications [Auk, Vol. 115 TABLE1. Juvenile(i.e. hatched during current breeding season) and adult (i.e.hatched during a previous breedingseason) sex ratios in the Maria Islandpopulation of TasmanianNative Hens. 1989 1990 1991 1992 1993 1994 1995 1996 All Juveniles No. of males 31 29 6 21 6 8 15 19 135 No. of females 29 19 11 20 5 8 13 18 123 No. unknown 0 0 1 6 0 0 1 0 8 Ratio M:F 1.07 1.53 0.55 1.05 1.20 1.00 1.15 1.06 1.10 Gad•• 0.066 2.077 1.450 0.024 0.087 0.000 0.140 0.027 0.557 P greaterthan 0.70 0.10 0.20 0.80 0.70 0.99 0.70 0.80 0.30 Adults No. of males -- 72 88 86 83 75 71 75 -- No.

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