588 ShortCommunications [Auk,Vol. 99

Absenceof Wing-spreadingBehavior in the AntarcticBlue-eyed Shag (Phalacrocoraxatriceps bransfieldensis)

NElL P. BERNSTEINAND STEPHENJ. M•,xsoN• FieldBiology Program, Department of Ecologyand Behavioral Biology, BellMuseum of NaturalHistory, University of Minnesota,Minneapolis, Minnesota 55455 USA Wing-spreadingin cormorants(Phalacrocoracidae) plumage as the Great Cormorant (4.8), Darter (An- andAnhingas (Anhingidae) is a commonlyobserved hingarufa, 4.5), and Reed Cormorant(4.3). posture, which has been related to their wettable If the AntarcticBlue-eyed Shag has typical cor- plumage(Owre 1967) and the need to dry flight morantplumage, why doesit lack wing-spreading feathersafter swimming (McAtee and Stoddard 1945, behavior?Perhaps the answerlies with the Antarctic Clark1969, Francis 1981). Observations of the wing- Peninsula's climate. Palmer Station has a mean an- spreadingbehavior of the Great Cormorant (Phala- nual temperature of 1.5øCwith means of 3øCin sum- crocoraxcarbo) during fog and rain (Townsend,in mer and -10øC in winter (U.S. AntarcticProgram Bent 1922), of a dry Reed Cormorant(P. africanus) PersonnelManual). With ambienttemperatures fre- (Curry-Lindahl1970), and of the FlightlessCormo- quentlybelow freezing and a high relativehumidity, rant (Nannopterumharrisi) (Snow 1966) raise ques- spreadwings would promote heat loss and probably tions, however, about plumage wettability and not aid drying by evaporation.Low temperatures whether or not the behavior might serve another should,therefore, select for reducedwettability (i.e. function,such as thermoregulation(e.g. Clark 1969, waterrepellancy), and indeed, as shags left the water Curry-Lindahl 1970, Kahl 1971) or communicationof afterbathing, they appearedfairly dry after a vig- successfulforaging attempts (Jones 1978). orousshaking. It wasclear that water had not deeply From January 1979 to March 1980 we studied Ant- penetratedthe plumage. arcticBlue-eyed Shags at PalmerStation, Antarctica Three reports offer explanationsof the lack of (64ø46'S,64ø03'W), where approximately800 shags water penetrationinto the plumage.Rijke (1970)hy- were resident most of the year. We never observed pothesized that lower index values indicated closer theseshags in spread-wingpostures during 3,000 barb spacingresulting in smallerspaces for water to bird-hoursof scheduledobservations nor during penetrate.Therefore, while the firstlayers of feathers many additional hours of unscheduledobservations. maybecome wet by capillaryaction, greater pressure The lack of wing-spreadingbehavior in this popu- will be required before successivelayers dampen. lationlead us to comparethe waterrepellancy of the Snow (1966)offered a similar explanationfor dry in* plumageof AntarcticBlue-eyed Shags with that of ner plumagein the FlightlessCormorant. Citing Fa- other cormorants and water birds. We examined the bricius (1958), she hypothesized that air trapped in normal pennaceousportion of the dorsal surfaceof dense plumage repelled water. Casler (1973) sup- breastfeathers with a light microscope.This yielded portedSnow's (1966) hypothesis, observing that dis- informationon featherwettability based upon a liq- tal portions of cormorant feathers were modified to uid repellancyindex [(r + d)/r] for feathersdeveloped retain water, but an air layer was retained next to by Rijke (1967,1968, 1970) in whichhalf the spacing the skin. For an AntarcticBlue-eyed Shag, wettable betweenbarbs (d) and the barb radius (r) represent surfaceplumage would be more hydrodynamicdue properties of a porous surface.Hailman (1969) has to lessbuoyancy and drag while swimming,and lack reviewed the limitations of the model, however, and of water penetration would prevent icy water from Elowson-Haley(pers. comm.)is currentlyinvesti- contactingthe skin. gatingthe model'sapplicability. We hypothesize that it is not necessaryfor the After comparingour techniquewith Rijke's(1967) Antarctic Blue-eyedShag to spread its wings for and finding them similar, we calculatedan index drying, and, indeed, the posturemay be disadvan- value of 3.8 for the Antarctic Blue-eyed Shag. If tageousin continuallycold climates.This alsosug- Rijke's (1967) model is valid, lower index values in- geststhat wing-dryingbefore flight may not be nec- dicatedecreased water repellancyor increasedwett- essaryfor other cormorantswith similar plumage, ability due to capillaryaction. Therefore, compared althoughwing-spreading behavior may be beneficial with Rijke's (1967) calculations,our index value in- in more temperate climateswhere ambient temper- dicatesthat the AntarcticBlue-eyed Shag has more aturespromote drying and heat retention. Within wettableplumage than the Mallard (Anasplatyrhyn- the contexts of thermoregulation, several authors chos, 5.9) and as wettable, if not more wettable, (e.g. Hauser 1957, Lanyon 1958, Goodwin 1967, Clark 1969,Kennedy 1968,Kahl 1971,Schreiber 1977) have observed spread-wing posture, or behavior t Presentaddress: Wetland Wildlife Populationand ResearchGroup, similar to spread-wingposture, in various birds to Minnesota Department of Natural Resources,Bemidji, Minnesota gain or lose heat. Only Curry-Lindahl(1970), how- 56601 USA. ever, has presentedevidence supporting this hy- JULY1982] Short Communications 589 pothesis for cormorantsßIndeed, Siegfried et al. CURRY-LINDAHL,K. 1970. Spread-wing postures in (1975)and Berry (1976)believed that heat gain was Pelecaniformes and Ciconiiformes. Auk 87: 371- only a secondaryfunction of the behavior in the 372. Cape Cormorant(P. capensis)and that wing-drying FABRICIUS,E. 1958. What makes plumage water- was the primary reasonßIt seemsthat the spread- proof?Wildfowl TrustAnn. Rept. 10: 105-113. wing posture can serve either or both functions in FRANCIS,A.M. 1981. Wing-and tail-flapping in An- cormorants, depending on environmental condi- hingas: a possiblemethod for drying in the ab- tions, but that neither is essential to the Antarctic sence of sun. Auk 98: 834. Blue-eyedShag. New Zealand speciesof Blue-eyed GOODWIN,D. 1967. Somepossible functions of sun- Shagsalso do not spreadtheir wingsafter exiting the bathing in birdsßBrit. Birds 60: 363-364. water (G. van Tets pers. comm.). HAILMAN,J.P. 1969. Review of Rijke (1967)ßBird- While the explanationsof wing-spreadingin cor- Banding 40: 65-67. morants remain unsubstantiated, the observations HAUSER, D.C. 1957. Some observations on sun- point to the complexrelationship between behavior bathing in birdsßWilson Bull. 69: 78-90. and the environmentßHaving a widespreaddistri- JONES,P. 1978. A possiblefunction of wing drying bution, cormorantshave adaptedto many habitats, posture in the Reed Cormorant Phalacrocorax but none colder year-round than the Antarctic Pen- africanus.Ibis 120: 540-542. insula. As the southernmost cormorant, the Antarctic KAHL, M.P. 1971. Spread-wing postures and their Blue-eyedShag demonstrates a behavioraladapta- possiblefunctions in the Ciconiidae.Auk 88: tion by its lack of the spread-wingbehavior typical 715-722. of its familyßThis adaptationpromotes heat reten- KENNEDY,R. J. 1968. The role of sunbathing in tion in the Antarctic climate, while the cormorants' birdsß Brit. Birds 61: 320-322. hydrodynamicplumage is retained. LANYON,W. E. 1958. The motivation of sun-bathing We thank the following for their criticismson and in birdsß Wilson Bull. 70: 280. thoughtsabout the paper:E. C. Bimey, J. J. Brokaw, McATEE, W. L., & H. L. STODDARD.1945. Wettable J. T. Bums, K. M. Cheng, J. Cooper,J. A. Haarstad, water birdsß Auk 62: 303-304. B. L. Heidel, A. K. Osgood,R. W. Schreiber,and H. OWRE,O. T. 1967. Adaptationsfor locomotionand B. Tordoff, with specialthanks to M. W. Weller. A. feeding in the Anhinga and the Double-crested M. Elowson-Haleyshared unpublished information. Cormorant. Omithol. Monogr. No. 6. M. Faust, P. C. Tirrell, and the Palmer Station crew RIJKE,A.M. 1967. The water repellancyand feather provided support and field assistanceßThe research structure of cormorants, Phalacrocoracidae. Os- was supportedby NSF grant DPP77-22096to D. F. trich 38: 163-165. Parmelee, who provided advice throughout the ß 1968. The waterrepellancy and featherstruc- studyand preparationof the paperß ture of cormorants,Phalacrocoracidae. J. Exp. Biol. 48: 185-189. LITERATURE CITED 1970. The phylogenetic development of water repellancy in water bird feathersßOstrich BENT, A. C. 1922. Life histories of North American birdsß Pelicans and their alliesß U.S. Natl. Mus. Suppl. 8: 67-76. SCHREIBER,R. W. 1977. Maintenance behavior and Bull. 121. communication in the Brown Pelicanß Omithol. BERRY,H. H. 1976. Physiologicaland behavioural Monogr. No. 22. ecologyof the Cape Cormorant Phalacrocorax SIEGFRIED,W. R., A. J. WILLIAMS, G. H. FROST,& capensis.Madoqua 9: 5-55. J. B. KINAHAN. 1975. Plumage and ecologyof CASLER,C. L. 1973. The air-sacsystems and buoy- cormorants. Zool. Africana 10: 183-192. ancy of the Anhinga and Double-crestedCor- SNow, B. K. 1966. Observations on behavior and morant. Auk 90: 324-340. ecologyof the FlightlessCormorant (Nannopter- CLARK,G. A., JR. 1969. Spread-wingpostures in um harrisi). Ibis 108: 265-280. Pelecaniformes, Ciconiiformes, Falconiformes. Auk 86: 136-139. Received10 August1981, accepted 5 January1982.