We used satellite telemetry methods to study macaroni penguins at South Georgia to determine how they ranged from their colonies during the early part of their breeding season at a time when they are constrained to return to their chicks on a near-daily basis. The principal objectives of this study were to examine whether these penguins exploit major oceanographic features where prey may be more predictable, whether birds from one colony forage in separate locations to those from nearby colonies, or whether they range evenly over the available area. Results show that the penguins did not range evenly, that birds from one colony tended to forage in locations separate from those used by birds from nearby colonies (or at least overlap was restricted), and that though birds from some colonies foraged within waters influenced by major oceanographic features such as the southern Antarctic Circumpolar Current front, not all birds in the region focused on such areas, as some birds foraged in other oceanographic contexts. The results from this study highlight the complexity of foraging dynamics for colonially nesting seabirds; they also help inform management models currently being developed for Antarctic krill fisheries, which are a potential competitor for the main prey of macaroni penguins. KEY WORDS: Macaroni penguin · Foraging · Oceanography · Satellite telemetry · South Georgia Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 323: [239][240][241][242][243][244][245][246][247][248][249][250][251] 2006 seabird species (de le Brooke 2004). Thus, given the oceanographic context in which macaroni penguins forage, it is critically important to understand how their foraging decisions are influenced by local conditions in order to better understand the motivating factors governing their foraging behaviour.Previous satellite telemetry studies describing the foraging locations of macaroni penguins are available (Barlow & Croxall 2002, Barlow et al. 2002, Trathan & Croxall 2004. They have so far only been conducted from Bird Island, a small offshore island near South Georgia. These studies indicate that macaroni penguins are very much constrained during the early stages of chick rearing, particularly during the broodguard period (Barlow & Croxall 2002, Trathan & Croxall 2004, when only females forage, with trips lasting on average about 12 h (Croxall et al. 1993). During brood-guard, males stay ashore and guard their chicks, which grow rapidly, increasing in weight by more than 1200 g (Williams 1995) over the course of the brood-guard period (approximately 20 d). Female penguins tracked from Bird Island during brood-guard are very conservative in their foraging locations, travelling along a relatively restricted set of bearings (Barlow & Croxall 2002, Trathan & Croxall 2004. This is despite the fact that Bird Island is small and foraging could potentially occur over a much wider area. The reasons why macaroni penguins forage along such a restricted set of bearings ar...

During January and February 1997, two separate surveys of the birds and seals of the South Sandwich Islands archipelago were made, with further data obtained from the northern islands during February 1998. Together, these surveys provide the most recent and accurate estimates of breeding populations of most species, their distributions, and their habitat. Observations were made (1) from a small vessel operating close inshore, which surveyed approximately 92% of the archipelago's coastline, in addition to making shore counts at selected locations; (2) during a six-week shorebased field camp on Candlemas Island; and (3) opportunistically during helicopter-supported landings and airborne operations over all islands in the archipelago. The surveys recorded 16 species of breeding birds, including the first confirmation of breeding by black-bellied storm petrels (Fregetta tropica) and Antarctic terns (Sterna vittata), the second record of incubating king penguins (Aptenodytes patagonicus), and the location of many previously unrecorded seabird breeding sites. The population of chinstrap penguins (Pygoscelis antarctica), at approximately 1.5 x 10 pairs is considerably less than the estimate of 5 x 10 pairs currently in use, and represents about 30% of the world population. Populations of chinstrap penguins, Antarctic fulmars (Fulmarus glacialoides), cape petrels (Daption capense), and snow petrels (Pagodroma nivea) in the South Sandwich Islands are of global significance. Five species of seals were recorded. At the time of the surveys, only Antarctic fur seals (Arctocephalus gazella) were confirmed to be breeding, and several new breeding sites were located. Pup numbers showed a small increase compared with the few earlier records, but the population has not undergone the large increases seen on South Georgia and at sites in the maritime Antarctic. The other four species recorded are considered highly likely to breed either within the archipelago or amongst pack ice that seasonally surrounds the islands.

As a preliminary to a population study using markrelease-recapture techniques, specimens of the Satyrid buttfly Melanargia galathea (L.) were subjected to a number of marking and capture techniques. Although the adults are thought to display both aposematic and cryptic coloration, the use of marks of different sizes and colours had no significant effect on recapture frequencies. However, repeated disturbance due to capture was found to significantly reduce recapture frequency. The influence of the different techniques on recapture frequencies could not be detected reliably by excessively low recapture rates, or by comparisons to Poisson distributions. It is suggested that these comparisons are of limited value as measures of the suitability of a marking or handling scheme. Subsequent work showed that capture affected recapture rates of several other species. Moreover, these effects could not be readily predicted from knowledge of the biology of these species. The implications of these findings are discussed.

We compared Antarctic fur seals Arctocephalus gazella breeding at 2 contrasting sites on South Georgia: one high density colony at Bird Island and one lower density colony at Cooper Bay. The population at Cooper Bay was considerably smaller than that at Bird Island despite ample suitable breeding area being available. At Cooper Bay, female seals were longer but weighed less than those breeding at Bird Island and, whilst both maintained the same rate of female pup growth, male pups grew faster at Cooper Bay. Although Bird Island seals dived deeper, they dived less often than Cooper Bay seals so that both populations spent comparable amounts of time in the bottom phase of dives actively foraging. Longer distance oceanic foraging trips that were observed at Bird Island were almost entirely absent from Cooper Bay. Both populations fed on Antarctic krill, but there was an absence of myctophid prey in the diet of seals at Cooper Bay. Evidence suggests that the favoured myctophid prey of fur seals at South Georgia, Protomyctophum choriodon, are absent from the colder waters around the south-east of the island. We propose that, if these energy-rich prey are unavailable in this region then seals at Cooper Bay may find it hard to offset the increased costs of foraging trips with longer duration and distance. This potentially reduced niche width means that the Cooper Bay population may be less buffered against environmental variability. Although food resources appeared to be sufficient during the period of our study, the south-eastern region of South Georgia has increased variability in food resources that, coupled with a smaller area in which to forage, might explain the reduced population size compared to the north-eastern end of the island.

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