cent drop from the original census of 8,650 nests in 1971 59°15W) on Nelson Island in the South Shetlands grew from (Muller-Schwarze and Muller-Schwarze 1975). about 800 nests in 1971-1972 to 1,514 in 1982-1983 (plus 89 Chinstrap penguin (P. antarctica). The number of breeding percent) and on the remote Danco Island (64°44S 62°37W) in chinstrap penguins has increased at remote sites and decreased Errara Channel, the rookery increased from 229 to 453 nests in responses to human interference. Entrance Point (63°00S (+98 percent) between December 1971 and December 1982. 60°33W) at Deception Island is a seldom-visited rookery. On Danco Island may be especially subject to population fluctua- our 25 January 1982 visit there, I noted a 207 percent increase in tions, rather than clear trends, due to varying snow cover at the breeding pairs since 1965 (Croxall and Kirkwood 1979). At Wa - beginning of the breeding season in different years. There are terboat Point (64°49S 62°52W), on the other hand, now the site few rocky outcrops available on that ice-capped island. of the Station Gonzalez Videla, the chinstraps decreased at one In conclusion, particular attention should be paid to the influ- of the two rookeries (Coal Point) from 350 nests in 1922 ence of frequent human visitation on penguin breeding be- (Bagshawe 1938) to 60 in December 1980 and from 225 to 2 nests havior, breeding success, and rookery size. in the other rookery on the Island, where this represents 83 percent and 99 percent drops, respectively. On the island there were still 125 nests in 1964 (Croxall and Kirkwood 1979). Thus, a 98 percent decrease occurred during the 16 years preceding References 1980. Gentoo penguin (P. papua). At Port Lockroy (64°49S 63°30W), Bagshawe, T.W. 1938. Notes on the habits of the Gentoo and Ringed or an often-visited site, the gentoos have been holding their Antarctic penguins. Transactions of the Zoological Society of London, 24, own. During the 1980-1981, 1981-1982, and 1983-1984 seasons, 185-306. counts differed by —20 percent, +11 percent, and +18 per- Croxall, J.P., and E.D. Kirkwood. 1979. The Distribution of penguins on the cent, respectively, from our 1971 count (Muller-Schwarze and Antarctic Peninsula and Islands of the Scotia Sea. Cambridge, England: British Antarctic Survey. Muller-Schwarze 1975). At Waterboat Point, site of the Station Muller-Schwarze, D. 1984. The behavior of penguins. Albany, N.Y.: State Gonzalez Videla, the Coal Point rookery had decreased by 91 University of New York Press. percent since 1922 to 153 nests in December 1980 and the rook- Muller-Schwarze, D., and C. Muller-Schwarze. 1975. A survey of ery at the Island by 14 percent since 1964 (Croxall and Kirk- twenty-four rookeries of pygoscelid penguins in the Antarctic Penin- wood 1979). Two less often visited gentoo rookeries have in- sula region. In B. Stonehouse (Ed.), The biology of penguins. London: creased within a decade: the rookery of Harmony Point (62°19S MacMillan.

Specimens of G. deliciosus were found in nearly all adult and Trematode parasites of marine birds in nestling gulls that were examined (table). This trematode had Antarctica: The distribution of not been previously reported from L. dominicanus although it is Gymnophallus deliciosus (Olsson a geographically widespread parasite characteristic of gulls (Jones and Williams 1968; Hoberg 1979). It is of interest that 1893) Szidat (1964) did not find it infecting southern black-backed gulls examined in Argentina. It is clear that the cycle of this trematode is completed in the area near Palmer. The distribu- E. P. HOBERG tion of immature specimens and metacercariae of G. deliciosus in nestling gulls suggests the importance of avian breeding Department of Pathobiology SC-38 gounds for the acquisition and maintenance of infections by this University of Washington trematode. Seattle, Washington 98195 Digeneans have not previously been reported from south polar skuas in Antarctica. G. deliciosus occurred with low preva- lence and intensity of infection in this host (table). During continuing studies of avian helminths at Palmer Sta- G. deliciosus had been reported from American sheathbills in tion, Antarctica (Hoberg 1983) trematodes were found as para- the South Orkney Islands and at South Georgia (Jones and sites only of charadriiform birds. Digeneans were not repre- Williams 1968, 1969-a; Williams et al. 1974) but it had not been sented in extensive collections (including several thousand found at localities adjacent to the Antarctic Peninsula or at the specimens of helminths) from spheniscids, procellariids, and latitude of Palmer Station (about 65°S). Sheathbills appear to be a phalacrocoracids. typical host for this trematode. Gymnophallus deliciosus (Olsson 1893) was the only species of Prey consumed by adult and nestling gulls at Palmer was trematode found in birds examined during the present study. It dominated by the limpet, Nacella polaris (Hombron and Jac- was found as a parasite in the gall bladder of three species of quinot 1841) (Hoberg unpublished data). This suggests the im- charadriiforms: American sheathbills, Chionis alba (Gmelin); portance of this mollusc as an intermediate host of G. deliciosus. southern black-backed gulls, Larus dominicanus Lichtenstein; Food-habits of south polar skuas at Palmer were more varied, and south polar skuas, Catharacta maccormicki (Saunders) col- and molluscs were not represented as prey. It is possible that lected in the immediate vicinity of Palmer Station during the limpets are infrequent prey for skuas and would likely be ac- austral summer of 1982-1983 (table). quired by kieptoparasitism from gulls. Jones and Williams

1984 REVIEW 159 Occurrence of the trematode Gymnophallus deliciosus (Olsson ate hosts (mollusca) and the foraging behavior of potential final 1893) in seabirds collected near Palmer Station, Antarctica hosts. Littoral environments near Palmer are structurally sim- ple and of low diversity due to ice scouring. The limpet, Nacella Intensity of Species of Number Prevalence Intensity of polaris, is the dominant intertidal invertebrate and one of the infection host infected percentage infection Xb few molluscs that could serve as a potential intermediate host range for trematodes (Jones and Williams 1968, 1969—a, 1969—b). The scarcity of suitable intermediate hosts and the predominance in Larus 16 76 1-22 8.4 the avifauna of pelagic foragers would further reduce the pos- domincanus sibility for the successful completion of some life cycles (von Adults Linstow 1878; Hoberg 1984). (N=21)c Field studies at Palmer Station (austral summer 1982-1983) Larus 17 85 1-44 9.0 and continuing laboratory investigations at the University of domincanus Washington were supported by National Science Foundation Nestlings grant DPP 81-15975. (N =20) Chionis a/ba 3 60 1-8 4.0 References Adults (N = 5) Graefe, G. 1968. Paramonostomum antarcticum n. sp. (Trem- Catharacta 3 15 2-7 4.3 maccormicki atoda:Notocotylidae) with observations of larval development in the Antarctic. Zeitschrift für Parasitenkunde, 30, 207-232. (In German.) Adults Hoberg, E.P. 1979. Helminth parasites of marine birds (Cha- (N =20) radriiformes: Alcidae and Laridae) occurring in the North Pacific Ocean and Gulf of Alaska. (Masters Thesis University of a Intensity of infection represents the number of parasites per infected Saskatchewan.) host. Hoberg, E. P. 1983. Preliminary comments on parasitological collections b "X" denotes mean number of parasites per infected host. from seabirds at Palmer Station, Antarctica. Antarctic Journal of the "N" denotes the number of birds of each species examined for parasites. U.S., 18(5), 206-208 Hoberg, E. P. 1984. Systematics, zoogeography, and ecology of platyhel- minth parasites of the seabird family Alcidae (Charadriiformes: Sub- order Alcae). (Doctoral Dissertation University of Washington.) (1968, 1969-a) and Graefe (1968) indicated that limpets and other Jones, N.V. and I.C. Williams. 1968. The trematode parasites of the intertidal molluscs were likely intermediate hosts for G. deli- sheathbill, Chionis alba (Gmelin), from Signy Island, South Orkney ciosus and additional species of trematodes from sheathbills. Islands. Journal of Helminthology, 42, 65-80. Previously, only species from three genera, Gymnophallus, Jones, N.V., and I.C. Williams. 1969-a. The nematode and Notocotylus, and Paramonostomum had been reported from cha- acanthocephalan parasites of the sheathbill, Chionis alba (Gmelin), at radriiform birds in Antarctica (Jones and Williams 1968, 1969—a, Signy Island, South Orkney Islands and a summary of host parasite 1969—b; Graefe 1968; Williams et al. 1974; Odening 1982). Avail- relationships in the sheathbill. Journal of Helminthology, 43, 59-67. able data suggest that these trematodes probably complete their Jones, NV., and I.C. Williams. 1969-b. Paramonostomum signiensis n. sp. life cycles in the subantarctic and antarctic. Continued studies (Trematoda:Notocotylidae) from the sheathbill, Chionis alba (Gmelin) at Signy Island, South Orkney Islands. Journal of Helminthology, 43, are planned at Palmer to attempt to elucidate the cycle for G. 53-57. deliciosus and other trematodes and to determine the influence Odening, K. 1982. Paramonostomum antarcticum (Trem- of intertidal foraging patterns by birds on the distribution of atoda:Notocotylidae) in Larus dominicanus in the South Shetland Is- trematodes in avian hosts in Antarctica. land (Antarctica). Angewandte Parasitologie, 23,137-143. (In German.) Among pelagic birds trematodes are generally incidental par- Szidat, L. 1964. Comparative helminthological investigation on the asites that occur with low prevalence and intensity of infection. Argentine large gulls Larus marinus dominicanus Lichtenstein und In the Northern Hemisphere, digeneans are characteristic of Larus ridibundus maculipennis Lichtenstein including new observa- lands feeding in shallow littoral environments, but they occur tions concerning species formation in parasites. Zeitschrift far Para- less frequently in diving birds which forage in pelagic regimes sitenkunde, 24, 351-414. (In German.) (Hoberg 1979, 1984). The structural attributes of marine eco- von Linstow, 0. 1878. Report on the Entozoa collected by H.M.S. Chal- systems and composition of avian communities in Antarctica lenger during the years 1873-1876. Challenger Reports (Zoology), 23, 1-18. suggest that digeneans should be rare parasites of seabirds in Williams, IC., N.V. Jones, M.J. Payne, and C. Ellis. 1974. The helminth this geographic region. parasites of the sheathbill, Chionis alba (Gmelin), and the diving The pattern of distribution of trematodes in marine birds in petrels, Pelecanoides georgicus (Murphy) and P. urinatrix (Gmelin) at Antarctica is influenced by the availability of suitable intermedi- Bird Island, South Georgia. Journal of Helminthology, 48, 195-197.

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