therefore, have been combined. Skua growth rates in 1988- References 1989 were not significantly different from those at Palmer for Eppley, Z.A., and M.A. Rubega. 1989. Indirect effects of an oil spill. 1980-1981 (Pietz unpublished data) but both appear to be lower Nature, 340, 513. than those seen at Signy Island and Cape Hallett (figure 5, Eppley, Z.A., and M.A. Rubega. In press. Indirect effects of an oil Hemmings 1984) and at Palmer in 1979-1980 (Pietz unpub- spill: Reproductive failure in a population of south polar skuas fol- lished data). In 1988-1989, krill and fish were the predominant lowing the Bahia Paraiso oil spill in . Marine Ecology-Prog- items in south polar skua chick regurgitations (table 2). This ress Series. observation differs from previous seasons when fish were the Heimark, GB., and R.J. Heimark. 1984. and marine mammals main prey of south polar skuas and krill accounted for less in the Palmer Station area. Antarctic Journal of the U.S., 19(4), 3-8. than 15 percent of their diet (Pietz 1987). Hemming, A.D. 1984. Aspects of the breeding biology of McCormicks skua Catharacta maccormicki at Signy Island, South Orkney Islands. Although the reproductive parameters for south polar skuas British Antarctic Survey Bulletin, 65, 65-79. in 1988-1989 were within normal values, the population suf- Maxson, S.J., and N.P. Bernstein. 1984. Breeding season time budgets fered a complete reproductive failure. In some previous years, of the southern black-backed gull in Antarctica. Condor, 86, 401-409. food shortages increased sibling aggression and intraspecific Neilson, D.R. 1983. Ecological and behavioral aspects of the sympatric predation, leading to reduced reproductive success (Pietz 1987). breeding of the south polar skua (Catharacta naccorinicki) and the However, in contrast to these years (Parmelee et al. 1978; Pietz brown skua (Catharacta lonnbergi) near the Antarctic Peninsula. Un- 1986), in 1988-1989 south polar skuas were frequently ob- published Masters of Science thesis, University of Minnesota. served feeding near their colonies. This continued inshore for- Parmelee, D.F., W.R. Fraser, and D.R. Neilson. 1977. Birds of the aging, apparently normal chick growth rates and prevalence Palmer Station area. Antarctic Journal of the U.S., 12(1-2), 14-21. of mortality in single chick nests suggest a different mechanism Parmelee, D.F., N. Bernstein, and D.R. Neilson. 1978. Impact of un- favorable ice conditions on productivity at Palmer Station dur- for the mortality in 1988-1989. The mortality among first-hatched ing the 1977-78 field season. Antarctic Journal of the U.S., 13(4), 146- skua nestlings was highly compressed in time and coincided 147. with the oil spill. We suggest that exposure to oil caused a Pietz, P.J. 1986. Daily activity pattern of south polar and brown skuas short-term disruption of normal parental attendence behavior. near Palmer Station, Antarctica. Auk, 103, 726-736. This exposed the young to fatal intraspecific aggression, the Pietz, P.J. 1987. Feeding and nesting ecology of sympatric south polar only cause of mortality observed after the oil spill (Eppley and and brown skuas. Auk, 104, 617-627. Rubega 1989 in press). Sokal, R.R., and F.J. Rohlf. 1969. Biometry. (2nd ed.) New York: W.H. This research was supported by National Science Founda- Freeman and Company. tion grant DPP 87-16005 to A.F. Bennett. We thank the people Watson, G.E. 1975. Birds of the Antarctic and Sub-Antarctic. Washington, of Palmer Station for their kindness and support throughout D.C.: American Geophysical Union. Williams, A.J., J. Cooper, and P.A.R. Hockey. 1984. Aspects of the our field season. We thank Bill Fraser for help in the field and breeding biology of the kelp gull at Marion Island and in South many enlightening discussions. We are grateful to Pamela Pietz Africa. Ostrich, 55, 147-157. for her willingness to share with us her unpublished data and Young, E.C. 1963. The breeding behaviour of the south polar skua. her experience with south polar skuas. Ibis, 105, 203-233.

Bird observations by its effluvium, being, perhaps, peculiarly congenial to this lichen" (Ross 1847, p. 339). The penguin rookery is still oc- at Seymour and Cockburn islands cupied and cormorants were seen although not nesting birds; however, neither snow petrels nor their nests were observed during the brief visit made to Cockburn Island in January 1987. DAVID H. ELLIOT The Adélie penguin rookery near Penguin Point, possibly the most southerly on the east side of the Antarctic Peninsula, Byrd Polar Research Center was probably first visited by Captain C.A. Larsen and two Ohio State University members of the crew of the Jason on 18 November 1893 (Larsen Columbus, Ohio 43210 1894). Dominican gulls and antarctic terns are the birds most com- monly seen on . Dominican gull nests were During the course of geologic fieldwork on Seymour and noted near the shore southeast of Cape Wiman (figure). Ant- Cockburn islands in 1986-1987 and 1989, observations were arctic tern nests, on the other hand, are much more widespread made on the occurrence of nesting sites of various birds. and were seen near Cape Wiman and at a number of localities Sir James Clark Ross, L. Crozier, J.B. Hooker, and others, south of Cross Valley. The terns apparently prefer to nest on landed on Cockburn Island on 6 January 1843. They found a the concretionary sandstones of the Lower Tertiary () large colony of Adélie penguins, cormorants (blue-eyed shags), Sobral Formation. The concretions, which are up to 1 meter and snow petrels. Ross and his party were struck by the rel- across, are commonly rather friable; thus the concretions break ative abundance of vegetation and Hooker noted in particular up readily and the ensuing rubble of smaller blocks and loose the lichen Lecanora miniata (later reassigned to Caloplaca hookeri) sand seems to provide particularly suitable nesting grounds. which ". . . grows nowhere else in such profusion; a circum- Other nesting areas are likely to be present on Seymour Island. stance which may arise from its preference for animal matter; Geologic fieldwork was supported by National Science the penguin rookery of Cockburn Island, which taints the air Foundation grants DPP 85-19080 and DPP 87-16258.

202 ANTARCTIC JOURNAL x) - 40, 56°45W Cape Wiman CockburnC) Island

101 091

64015S Cross Valley B

I Seymour Island

Penguin 22/ : C Point \

/ 5 0 km Og

Nesting Sites x Antarctic terns o Dominican gulls + Adelie penguins

>1

-- - --

oy

Generalized areas of nests Course Contours in meters

500 C •"

Sketch map of Seymour Island to illustrate location of nesting sites.

References arctic Regions during the years 1839-43. (Vol. II.) London: John Murray. Larsen, C.A. 1894. The voyage of the Jason to the Antarctic regions.

Ross, J.C. 1847. A voyage of discovery and research in the Southern and Ant- Geographical Journal of London, 10(4), 333-344.

1989 REVIEW 203