1.06 0 to -1.94°C in 1976. Atkinson (1969) found R.globularis, living in Cardigan Bay, Wales, with salini-ty fluctuations of 30.2 to 34.6 parts per thousand andtemperatures ranging from 5.5 1 to 8.5°C. Murray(1973) documents the wide geographic distribution ofR. globularis, suggesting that it is a very tolerantspecies. Geographic distribution reflects reproductiveas well as feeding tolerances, but this investigation ofan antarctic population of R. globularis indicates thatit has greater tolerance ranges than the other speciesinvestigated. This conclusion agrees with the generaldistribution data for the species.

This research was supported by National ScienceFoundation grant DPP 74-12139. We appreciate thehelp of Holmes and Narver, Inc., support crews atPalmer Station and aboard Hero, particularly S.Williams, W. Lokey, and G. Bennett. We are gratefulto C. Denys, who gave valuable help during the1975-1976 austral summer collecting aboard Hero.

References

Andriashev, A.P. 1968. The problem of the life communityassociated with the antarctic fast ice. In: Symposium on Antarctic

Oceanography, Santiago, Chile, 1966. Cambridge, Scott PolarResearch Institute, Scientific Committee on Antarctic Research.147-155.

Atkinson, K. 1969. The association of living foraminifera with algaefrom the littoral zone, South Cardigan Bay, Wales. Journal ofNatural History, 3: 517-542.

Bradshaw, J.S. 1961. Laboratory experiments on the ecology offoraminfera: Contributions to the Cushman Foundation forForaminifera Research, 12: 87-106.

Gruzov, E. N. In press. Seasonal alterations in coastal communities.In: Proceedings of the Third SCAR/JUBS Symposium on Antarc-tic Biology, Washington, D.C., August 1974.

Hynes, H.B.N. 1950. The food of fresh-water sticklebacks(Gasterosteus aculeatus and Pygosteus pungitus) with a review ofmethods used in studies of the food of fishes. Journal of AnimalEcology, 19: 36-58.

Krebs, W.N. 1974. Physical chemical oceanography of Arthur Har-bor, Anvers Island. AntarcticJournal of the U.S. IX(5): 219-221.

Lipps, J.H., and W.N. Krebs. 1974. Planktonic foraminiferaassociated with antarctic sea ice. Journal of ForaminferalResearch, 4(2): 80-85.

Meguro, H. 1962. Planktonic ice in the antarctic ocean. AntarcticResearch Series, 14: 72-79.

Murray, J.W. 1973. Distribution and Ecology of Living Bent honicForaminfera. New York, Crane Russak. 275 p.

Myers, E.H. 1942. A quantitative study of the productivity offoraminifera in the sea. Proceedings of the AmericanPhilosophical Society, 85: 325-342.

Penguin census by aerial photographicanalysis at Cape Crozier, Ross Island

R. G. BUTLER and D. M)LLER-SCHWARZEDepartment of Zoology

College of Environmental Science and ForestryState University of New YorkSyracuse, New York 13210

Accurate estimates of world numbers of mostantarctic and subantarctic penguin species arecurrently impossible due to scarce and unreliabledata on breeding populations. Although a largenumber of rookeries have been located, research hasbeen conducted in only a small percentage of these.Each new survey reports previously unknowninformation regarding species composition and sizeof populations inhabiting individual rookeries (forexample, see Miiller-Schwarze and Muller-Schwarze, 1975). This is especially true of thepygoscelid penguins. The problem is compoundedby the fact that even in extensively studied rookeriesthe resident populations have often not beenaccurately assessed. This has resulted in difficultieswith the interpretation of data on predationpressure, mortality, etc. We suggest that thisproblem may be rectified through the properapplication of aerial photographic analysis. Aerialphotography was first used for penguin censuses by

Bauer (1967) on the Crozet and Kerguelen Islands.The species studied were king penguins(Aptenodytes patagonica) and macaroni penguins(Eudyptes chrysolophus). Such analysis has alsobeen used for censuses of the Adélie penguinrookeries at Cape Bird, Beaufort, Franklin, andInexpressible islands (Stonehouse, 1965, 1969).Using this method, a more accurate census wasobtained for a large rookery of Adëlie penguins(Pygoscelis adelzae) at Cape Crozier (77°31'S.169°23'E.) on Ross Island, Antarctica.

The U.S. Navy, in conjunction with the U.S.Geological Survey, has taken aerial photographs of theCape Crozier rookery every season since 1961 (figure).Photos (9 x 9 inches) from the Crozier mission flownon 16 November 1966 were selected for a direct countof all penguins in the main rookery and in the smaller,adjacent east rookery. Exposures 5, 6, 7, 24, 38, and41 (TMA 2004), taken at an altitude of 2,250 feet,were used in this study. Counts were conducted with a

March/June 1977 25

U.S. Navy

binocular microscope (American Optical Corpora-tion) and a hand counter.

The main rookery at Cape Crozier has previouslybeen estimated to contain 300,000 Adélies and eastrookery 50,000 (Penney and Lowry, 1967; Emison,1968; LeResche and Sladen, 1970). However, it isdifficult to extract from the literature the exact datesand methods used to arrive at these estimates.Penney and Lowry (1967) conducted counts ofsample areas of aerial photographs, interpreted eachpenguin as a nesting bird, and estimated 147,039nests (approximately 300,000 birds) in the mainrookery. The validity of this method isquestionable, largely due to their interpretation ofevery penguin as a nesting bird and their use ofestimations rather than total counts of the Adéliespresent on the aerial photos. Our own direct countsfrom the 1966 photographs revealed far fewerpenguins at Cape Crozier than had been reportedpreviously. The main rookery contained 130,926Adélies and the east rookery held 19,993. However,this information alone does not constitute a directassessment of the Crozier Adélie breeding popula-tion because it is usually impossible to determinefrom the photos in mid-November which birds areoccupying nests and which are either matesaccompanying nesting birds or are unmated, non-nesting penguins. Using data obtained fromperiodic consenses of 12 Adélie colonies (ap-proximately 1,210 successful nests) conducted byour research group at Crozier during the 1974-1975field season, it was estimated that 25.3 percent of thetotal birds present during the period 18 to 20November were not nesting. This leaves 92,278breeding birds in mid-November. In 1974-1975, thetotal number of birds decreased by 29.1 percent from18 to 20 November until 5 to 11 December. Usingthis value for the 1966 aerial census data, there were92,827 birds on 5 to 11 December. Again using the1974-1975 ground-count data, 91.5 percent of the

birds present then occupied successful nests (that is,nests containing eggs or chicks). For 1966, thiswould be 84,934 nests, or the same number ofbreeding pairs.

Oelke (1975) censused the Crozier populationduring the period 4 to 10 December 1970 andestimated between 80,000 and 85,000 breeding pairsin the main rookery. Out estimate of 84,934breeding pairs in the main rookery for December1966 is in close agreement with Oelke's 1970 counts.Our Crozier censuses also indicated that ap-proximately 4.4 percent of the total birds presentfrom 5 to 11 December occupied unsuccessful nests.These penguins probably represented late breeders,reoccupation pairs, mated pairs that had recentlylost eggs or chicks, or unmated juveniles or adults.Taking these birds into account, it is possible toconservatively estimate the Adélies in the mainrookery at 178,040 and the east rookery at 27,188.This yields a total population estimate of ap-proximately 205,000 Adélies at Cape Crozier in 1966as compared to previous estimates of 350,000.Hence, claims that the Adélie population at Crozierhas "sharply decreased" (Oelke, 1975) seeni Un-substantiated, at least for the period between 1966and 1970.

Although the photographic analysis techniquehas definite merit, it is also necessary to point outseveral of its inherent weaknesses. First, poor-quality photos that are incomplete, blurred,distorted because of topography, or taken at extremealtitudes or angles make population estimatesdifficult or unreliable. Stonehouse (1965, 1969)found that best photographs were obtained withfine-grain film and hand-held press cameras instrong but hazy sunshine, and at altitudes of 150 to200 meters. Sladen and LeResche (1970) considerthis altitude too low and helicopters too noisy. Theyrecommend fixed-wing airplanes, such as the TwinOtter, flying at 610 to 760 meters with a 305-millimeter lens. Another major problem is develop-ing an accurate population estimate from directcounts of photographs taken on a given date. It isessential to be able to determine during which stateof the breeding cycle the photos have been taken inorder to resolve what proportion of the birdsphotographed are actually nesting. Sladen andLeResche (1970) recommend aerial photography atthe peak time of egg laying, when almost all nestsare tended by only one bird of a pair and when feweggs have been lost. Weather and sea-ice conditionscan influence the arrival of penguins at a particularrookery and can result in minor shifts in the timingof the breeding cycle from year to year. Nest losses inearly December can vary from 0.4 percent per day ina "good" year to 2 percent per day in an unfavorableseason (Stonehouse, 1969). These problems mightbe overcome by photographing a given rookery

Example of an aerialphotograph of a smallportion of the CapeCrozier rookery takenon 16 November 1963at an altitude of 2,000feet. Black dots areindividual penguinsagainst background ofguano-stained sub-strate. Black areas arerock or gravel notoccupied by Ad4lies,and white areas aresnow fields. Landingbeach (ice-bound) isat left.

TMA 1251.

26 ANTARCTIC JOURNAL

several times over the course of the breeding season.Finally, population estimates derived from aerialphotos will probably be somewhat conservative asjuveniles and mated pairs that have been un-successful and have returned to sea will not beaccounted for. Of the three different census figures(total number of birds present, number of breedingpairs, and number of successful breeding pairs),only the first can be obtained from aerialphotographs alone. The others require groundstudies. It will depend on the questions asked whichof the three figures is needed.

Despite its drawbacks, we think that with furtherrefinement aerial photographic analysis willprovide a superior and relatively inexpensivemethod for tracking population trends in variousspeniscid species. Research in progress by our groupinvolves conducting analyses of several years' aerialphotographs (1963 to 1976) to quantify anypopulation trends at the Cape Crozier Adélierookery. Also, we plan to survey photographs of theantarctic coast, the Antarctic Peninsula, andsurrrounding islands to locate and estimate the sizeof additional penguin rookeries in order to facilitateestimates of total numbers of antarctic penguins.

This research was partially supported byNational Science Foundation grant DPP 74-08677.

The authors are indebted to David G. Ainley forvaluable criticism of this manuscript.

ReferencesBauer, A. 1967. Denobrement des manchotieres de i'Archipel

Crozet et des lies Kerguelen a l'aide de photographies aeriennesverticales. T.A.A.F.. 41: 3-21.

Emison, W.B. 1968. Feeding preferences of the Adiie penguin atCape Crozier, Ross Island. Antarctic Research Series, 12:191.212.

LeResche, R.E., and W.J.L. Sladen. 1970. Establishment of pairand breeding site bonds by young known-age Adélie penguinsPygoscelis adeliae. Animal Behavior, 18:517-526.

Muller-Schwarze, C., and D. MUhIer .Schwarze. 1975. A survey oftwenty-four rookeries of pygoscelid penguins in the AntarcticPeninsula region. In: The Biology of Penguins (Stonehouse, B.,editor). Baltimore, University Park Press. 307-320.

Oeike, H. 1975. Breeding behavior and success in a colony of Adtliiepenguins Pygosceli.s adeliae at Cape Crozier, Antarctica. In: TheBiology of Penguins (Stonehouse, B., editor). Baltimore, Univer-sity Park Press. 363-395.

Penney, R. L., and G. Lowry 1967. Leopard seal predation in Adéliepenguins. Ecnloru. 48: 879-882.

Sladen, W. J . L., and R. E. LeResche. 1970. New and developingtechniques in antarctic ornithology. In: Antarctic Ecology(Holdgate, M. W., editor). New York, Academic Press. 585-596.

Stonehouse, B. 1965. Counting antarctic animals. New Scientist,July: 273-276.

Stonehouse, B. 1969. Air census of two colonies of Adéliepenguins (Pygoscelis adeliae) in Ross Dependency, Antarctica.Polar Record, 14: 471-475.

ARA Islas Orcadas cruise 8ALDO P. T0M0 and ENRIQUE MARSCHOFF

Biology DivisionArgentine Antarctic Institute

Buenos Aires, Argentina

JORGEJ. SANCHEZArgentine Antarctic Institute

andSchool of Pharmaceutics and Biochemistry

Buenos Aires University

ARA Islas Orcada4 cruise 8 began at Buenos AiresOn 2 February 1976 and ended there on 13 March1976. It had three objectives: (1) collection ofzooplankton and phytoplankton samples in correlationwith physical and chemical seawater data, (2) con-tribution to understanding of taxonomic, zoo-geographical, and trophic relations of the benthicfauna, and (3) capture of krill longer than 40millimeters for biochemical and microbiologicalstudy.

Results were as follows:Seawater samples were collected from the bottom,

the surface, and intermediate depths at 21 stations

(figure and table). Proximity to bottom was deter-mined by sonar. The samples were collected using aHensen net (200-micron mesh) with a strangulatiorclosing system.

Nansen and Niskin sampling bottles were used tocollect water samples for determinations of salinity,temperature, dissolved oxygen, alkalinity, and pH.

Water samples were filtered for subsequent deter-mination of nutrients and chlorophyll.

The samples were kept in formaline (5 percent) forqualitative and quantitative phytoplankton studies.

March/June 1977 27