NAVIGATION to NEST SITE in the SNOW PETREL (PAGODROMA NIVEA)L~’

484 SHORT COMMUNICATIONS

NIH grant HD 06552 to K. A. Sullivan, the American sex ratio of eastern wintering Dark-eyed Juncos Philosophical Society, and the Frank M. Chapman (Juncohvemalis). Ecology 571679-693. Foundation. MOORE,N. J: 1972. Ethology of the Mexican Junco ~Juncoohaeonotus oalliatus~. Ph.D.diss.. Univ. of LITERATURE CITED Arizona, Tucson. _ ’ BALPH,M. H. 1979. Flock stability in relation to MYERS,J. P. 1981. A test of three hypotheses for dominance and agonistic behavior in wintering latitudinal segregationof the sexes in wintering Dark-eyed Juncos.Auk 961714-722. birds. Can. J. Zool. 59:1527-1534. GAUTHREAUX,S. A., JR. 1978. The ecological sig- RABENOLD,K. N., ANDP. P. RABENOLD.1985. Vari- nificance of behavioral dominance, p. 17-54. In ation in altitudinal migration, winter segregation, P.P.G. Batesonand P. H. Klopfer [eds.], Perspec- and site tenacity in two sub-speciesof Dark-eyed tives in ethology. Plenum Press, New York. Juncos in the southern Appalachians. Auk 102: KETTERSON,E. D., AND V. NOLAN, JR. 1976. Geo- 805-819. graphic variation and its climatic correlatesin the

The Condor 90:484-486 0 The CooperOrnithological Society 1988

NAVIGATION TO NEST SITE IN THE SNOW PETREL (PAGODROMA NIVEA)l~’

SVEIN HAFTORN Universityof Trondheim, The Museum, E. Skakkesgt.47A, N-7000 Trondheim,Norway FRIDTJOFMEHLUM NorwegianPolar ResearchInstitute, P.O. Box 158, N-1330 Oslo Lufthavn, Norway CLAUSBECH Universityof Trondheim, ZoologicalInstitute, N-7055 Dragvoll, Norway

Key words: Snow Petrel; Pagodroma nivea; o&c- est amongthe 151 speciesfrom 23 orders studied,even tory navigation: visual navigation; breeding colony; higher than the Brown Kiwi, Apteryx australis (rank Antarctica. 2), and the Turkey Vulture, Cathartesaura (rank lo), both of which have been shown to be capable of dis- Procellariiform birds have a well-developed olfactory criminating between relevant food odors (Stager 1964, apparatus(Bang 1966, 197l), suggestingthat olfaction Bang and Wenzel 1985, Houston 1986). is ofvital importance to thesebirds. Experiments made During the Norwegian Antarctic Research Expedi- at sea (Hutchison and Wenzel 1980, Hutchison et al. tion in January to February 1985 to the Miihlig-Hof- 1984. Jouventin and Robin 1984) and in captivitv mann Mountains, in Queen Maud Land on the Ant- (Jouventin 1977) strongly support the view that pro- arctic continent, we had the opportunity to study a cellariiforms use olfaction in locating food. Evidence population of Snow Petrels, roughly estimated as 500 also supportsthe view that an olfactory guidancesys- pairs (Mehlum et al. 1985). The colony was situated tem is utilized to locate nestingburrows at night in the at Svarthamaren (71”53’S, 5”lO’E). where the Snow Leach’s Petrel, Oceanodromaleucorhoa (Grubb 1974). Petrels were nesting close to and partly within a huge Birds of this speciesapproached their island upwind colony of the Antarctic Petrel, Thalassoicaantarctica. at twilight or after dark, plummeted through the heavy The distance to the open sea was about 200 km. wooded cover and landed a few meters downwind of To test whether the Snow Petrelsdepend on olfaction their burrows, finally walking upwind the last short for navigation to their hidden nests, we carried out a distance. small-scale experiment. Becauseof the 24-hr contin- When the ratio of olfactory bulb diameter to the uousdaylight during the breedingseason (the sun being largest diameter of the cerebral hemisphere was mea- continually above the horizon from 15 November to sured,the Snow Petrel, Pagodromanivea, ranked high- 27 January),we hypothesizedthat the birds should be able to locate the nests by vision alone, using learned landmarks. The resultsof our experiments in fact support this view. ’ Received 12 June 1987. Final acceptance4 De- cember 1987. METHODS AND MATERIALS 2 Publication no. 90 of the Norwegian Antarctic Re- The majority of the Snow Petrels were nesting under search Expeditions (1984-1985). large boulders on the ice-free, north-exposed hillside SHORT COMMUNICATIONS 485 of Svarthamaren. Out of a total of 42 nests inspected group, returned successfullyto their respective nests. during the neriod 16 to 18 Januarv 1985.34 each con- All these eight birds returned within 7 hr of their re- tained one kgg, in three other nests the egg was at the moval, exceptfor two ofthe control groupbirds, which point of hatching, and the remaining five nests con- arrived 7 to 14 and 22 to 34 hr afterwards. The result tained small chicks.This finding is consistentwith the of the experiment thus indicates that the birds with statements of Brown (1966) and Somme (1977) that blocked nostrils were not inferior to the control birds hatchingin the Snow Petrel occursabout mid-January. in relocating their nests. It therefore seems that the Altogether 24 incubatingbirds were caught,between Snow Petrel is quite able, by visual navigation alone, 10:00 and 15:00, on three different dates (17, 18, and to locate nests hidden under boulders, probably using 23 January) on nests containing eggs.The birds were characteristicmarkings in the surroundings.This find- ringed and color-marked by painting the head feathers. ing accordswith what would be expected in an envi- The nostrils of half of the birds (12) were blocked, ronment with 24-hr continuous daylight during the following the method described by Grubb (1974). In breeding season. short, we used plugsof modelling clay, which was in- Our experiment could be criticized for not including serted with a blunt probe and sealed with a layer of an additional experimental group of birds that were waterproof, nontoxic cement (Ceramco polycarboxyl- prevented physiologically from using their sense of ate cement). The respective numbers of birds caught smell. This could have been achieved by transecting on the above-mentioned dates were 10, 10, and 4, of the olfactory nerves, as was done by Grubb (1974). which 5, 5, and 2, respectively, had their nostrils However, the results of his orientation experiments blocked. The birds were randomly assignedto treat- with the Leach’s Petrel (Grubb 1974) lend little support ment and control groups. They were all released 1 to to the argumentthat birds with blocked naresmay still 2 km away from the breeding colony at Svarthamaren, be able to discriminatebetween odors. None of Grubb’s 90 min to 4 hr after capture. experimental birds returned to their burrows, whether The cyclonesthat reachedthe shelf edgefurther north or not their nares had been sealed or their olfactory only occasionallycaused strong wind in the Svartha- nervessevered. Admittedly, three of the Leach’s Petrels maren area. However, strongkatabatic winds from the released with plugged nares did come back, but the Antarctic plateau to the south occurred almost every plugs had evidently become dislodged before return. evening and night, and flowed down an icefall 2 km to One may speculatewhy only one third of our cap- the southeastof Svarthamaren. Here wind velocities tured birds did finally return to their nests. One pos- normally reached6 to 10 m set I, but in the immediate sible explanation could be that the birds which failed area ofthe colony velocitieswere about 50% less(Meh- to return happenedto be capturedon the nest at a final lum et al., in press). At the time of day when the ex- stage of their current incubation session and conse- perimental birds were releasedthe wind velocity was quently were only slightly motivated for an immediate low. resumption of incubation. A comparison of the body condition of the birds that returned and those that RESULTS disappeared,as adjudged from the relationship ofbody weight to wing length, however, did not support this Four of the 12 experimental birds successfullyreturned tentative explanation, as no significant difference was to their own nests, three within 5 hr after release, the found between the two groups (two-tailed t-test, P > fourth one 5 to 7 hr afterwards. Four of the 12 control 0.40). birds also returned to their nests, the first two 5 to 7 Another variable which indirectly might indicate hr after release, the third one 7 to 14 hr afterwards, whether a bird had been captured early or late in its and the last one 22 to 34 hr afterwards. Thus, exactly current incubation spell, is the period of time which the same number (four) and proportion (one third) of elapsed between capture of the bird on nest and the birds from each group returned to their nests.All eight arrival ofits presumedmate. For thoseeight birds (four of thesebirds reappearedbefore any of their unbanded experimentaland four controls),which returnedto their mates were observed back at the colony. nestsafter release,this period lasted on average 3.4 * At 14 of the remaining 16 neststo which the captured SD 0.9 days (range 2.5-4.5 days). For those 14 birds birds did not return, new unmarked birds appeared which disappearedaltogether after release, the mean and took over the experimentally interrupted incuba- was 3.5 f 1.7 days (range0.3-5.5 days). In other words tion within 6 daysafter their presumedmates had been this variable, too, disclosesno difference between the removed. The first of these unmarked birds settled on two groups (Mann-Whitney U-test, two-tailed, P > the nest about 6 hr after its presumed mate had been caught, the second one about 30 hr afterwards, while 0.50). Most likely, sensitivity to seriousdisturbances when five other birds appearedafter 2 to 3 days, three more at the nest (capture,handling) provide the explanation after 4 to 5 days and four more after 5 to 6 days. None for the overall low rate of return, althoughthis view is was observed to return to the final two nests. The re- inconsistentwith the experienceof Cowan (198 l), who turned experimentalbirds were all checkedfor bilateral captured and measured many Snow Petrels at Casey retention of their nostril plugs. and found that they returnedat onceto their nestswhen released. DISCUSSION After capture on the nest and release 1 to 2 km away We thank two anonymousreferees for valuable com- from the breeding colony, the same proportion of the ments to the manuscript. Ph. Tallantire kindly im- experimental and control birds, viz. one third of each proved the English. 486 SHORT COMMUNICATIONS

LITERATURE CITED factory foragingby Sooty Shearwatersand North- em Fulmars, p. 72-77. In D. N. Nettleship, G. A. BANG,B. G. 1966. The olfactory apparatusof tube- Sanger, and P. F. Springer [eds.], Marine birds: nosedbirds (Procellariiformes). Acta Anat. 65139l- their feeding ecologyand commercial fisheriesre- 415. lationships. Canadian Wildlife Service Special BANG,B. G. 1971. Functional anatomy of the olfac- Publications, Ottawa. tory system in 23 orders of birds. Acta Anat. 79, JOUVENTIN,P. 1977. Olfaction in Snow Petrels. Con- Suppl. 58: l-76. dor 79:498-499. BANG,B. G.. ANDB. M. WENZEL. 1985. Nasal cavity JOUVENTIN,P., AND J. P. ROBIN. 1984. Olfactory ex- and olfactory system, p. 195-225. In A. S. King periments on some Antarctic birds. Emu 84:46- and J. McLelland leds.1. Form and function in 48. birds. Vol. 3. Academic%‘ress,London. MEHLUM, F., C. BECH,AND S. HAFTORN. 1985. Or- BROWN,D. A. 1966. Breeding biology of the Snow nithological investigations in Miihlig-Hof- Petrel Pagadroma nivea (Forster). Anare (Aust. mannfiella, Dronning Maud Land. Nor. Polarinst. Nat. Antarct. Res. Exped.) Sci. Rep. Ser. B 1 Zool. Rapportserie 22127-34. 89: l-63. MEHLUM,F., Y. GJESSING,S. HAFTORN,AND C. BECH. COWAN,A. N. 1981. Size variation in the Snow Petrel In press. Census of breeding Antarctic Petrels (Pagodroma nivea). Notornis 28:169-188. Thalassoica antarctica, and physical features of GRUBB,T. C., JR. 1974. Olfactory navigation to the the breeding colony at Svarthamaren, Dronning nesting burrow in Leach’s Petrel (Oceanodroma Maud Land, with notes on breeding Snow Petrels leucorrhoa). Anim. Behav. 22: 192-202. Pagodroma nivea, and South Polar Skuas Catha- HOUSTON,D. C. 1986. Scavengingefficiency of Tur- racta maccormicki. Polar Res. key Vultures in tropical forests. Condor 88:3 1S- SOMME,L. 1977. Observations on the Snow Petrel 323. (Pagadroma nivea) in Vestfiella, Dronning Maud HUTCHISON,L. V., AND B. M. WENZEL. 1980. Olfac- Land. Nor. Polarinst. Arbok 1976:185-292. tory guidancein foragingby procellariiforms.Con- STAGER,K. E. 1964. The role of olfaction in food dor 82:314-319. location by the Turkey Vulture (Cathartes aura). HUTCHISON,L. V., B. M. WENZEL,K. E. STAGER,AND Los Ang. Cty. Mus. Contrib. Sci. 8 1:l-63. B. L. TEDFORD. 1984. Further evidence for ol-

The Condor 90:486-489 0 The Cooper Ornithological Society 1988

IMITATIONS OF WHITE-CROWNED SPARROW SONGS BY A SONG SPARROW’

LUIS F. BAPTISTA Deoartment of Ornitholom and Mammalotx__ California Academv of Sciences. Golden Gate Park, San Francisco: CA 94118 ’ d

Key words: Song Sparrows: allospecific song; White- The song repertoire of an adult Song Sparrow con- crowned Sparrow: mimicry; song. sistsof a number of themes. A theme is defined as “a particular set of notes always rendered in the same Although cardueline finches are known to incorporate order and with set pitch relationships” (Nottebohm vocalizations of many allospecific species into their 1969:302). advertising song (Knecht and Scheer 1968, Giittinger Marler and Peters (1977, 1987) also exposed Song 1974, Remsen et al. 1982), recordsof emberizid finches Sparrowsto tapesofconspecific and alien Swamp Spar- imitating allospecificsongs in the wild are rare (Bap- row songs.As adults, the experimental subjectssang tista et al. 1981, Cooper and Murphy 1985). mostly themes containing Song Sparrow syllables, al- The resistanceto learning allosbecific syllables ap- thougha few themesincluded syllables typical of Swamp pears to vary among speciesin the genus Melospiza. Sparrows.No themescontained exclusively allospecific Naive Swamp Sparrows(M. georgiana) exposedto both syllableshowever, indicating that Song Sparrowspos- taped conspecificsong and songof the sympatric Song sessa genetic predisposition to learn conspecific syl- Sparrow (M. melodia) produced conspecific song as lables. adults, rejecting allospecific song as learning stimuli On 11 April 1987, I tape-recordeda “mimetic” SolLg (Marler and Peters 1977). Sparrow on the campus of the State University of San Francisco,California, singingWhite-crowned Sparrow (Zonotrichia leucophrys) songs, Song Sparrow songs, ’ Received 24 June 1987. Final acceptance4 Decem- and songs containing syllables borrowed from both ber 1987. species(Fig. 1). I describe herein the song repertoire