Extrapair paternities in black-browed Thalassarche melanophris, grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans at South Georgia

Extrapair paternities (EPP) are relatively common in passerines, but rare in seabirds. Like most seabirds, albatrosses are long lived, form long-term pair bonds and require biparental care for chick-rearing. Microsatellite analyses of 327 chicks from black-browed Thalassarche melanophris , grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans over two breeding seasons revealed the presence of EPP in all three species. Though EPP rates varied between species and years, up to 21% of offspring were the result of extrapair matings. Rates were highest in wandering albatrosses (6–21%) followed by grey-headed (3–10%) and black-browed (0–9%) albatrosses. EPP rates were lower in 1998 compared to 1999 in both black-browed and grey-headed albatrosses, whereas the reverse was true for wandering albatrosses. Interspecific differences in EPP rates may reflect differences in breeding phenology and sexual size dimorphism. Differences in timing and frequency of breeding may promote different opportunities for interactions with birds other than their normal partner. The different breeding habitat, dispersion and mate-attraction rituals in wandering albatross, together with the disparity in size between the sexes may also offer more scope for higher rates of EPP. Despite extensive sampling within each colony, we were unable to identify sires for many of the extrapair young; however males from other colonies were involved, raising interesting questions regarding the timing and nature of such events.     

Demographic parameters of black-browed albatrosses Thalassarche melanophris from the Falkland Islands

Black-browed albatrosses Thalassarche melanophris are currently classified as globally endangered. The most important populations of this species are believed to be declining due to, amongst other factors, unsustainable levels of incidental mortality in fishing gear. However, detailed demographic data are lacking for several critical populations, including the largest of all, nesting in the Falkland Islands. Here, we present data from the first Falkland Islands detailed demographic study (at New Island) and show that, from 2003 to 2009, the mean adult survival probability was 0.942 (95% CI: 0.930–0.952). Nesting frequency of adults is amongst the highest recorded for Thalassarche albatrosses and breeding success (0.564 chicks per egg) is within normal values. The nesting population in the intensively studied plots experienced an increase of 4% per year from 2004 to 2009. These results indicate that the Falklands population may not be as threatened as previously supposed, although studies from more sites and a longer time series are needed to confirm or refute this. The high survival rates may partly reflect recent efforts to mitigate bycatch made by the Falkland Islands and other fisheries in the region. The reinforcement of such initiatives may be critical to buffer the black-browed albatross population against ecosystem shifts and natural disasters (such as harmful algal blooms) that will likely become more frequent with ongoing global changes.     

Diving behaviour and diet of the blue-eyed shag at South Georgia

Summary This paper describes a concurrent investigation of individual variation in diet, diving patterns and performance of blue-eyed shags Phalacrocorax atriceps breeding at South Georgia. Within one day individual shags exhibited one of three foraging strategies: short diving (4 birds, all dives 120 s) and mixed diving (15 birds, predominantly long but with a few short dives). The mean number of dives per day was significantly higher in shags that only made short dives (mean=172.0, SE=43.2) than birds with a mixed diving strategy (mean=40.5, SE=4.7) and birds that made only long dives (mean=30.8, SE=1.8). Diet was assessed using hard remains recovered from pellets regurgitated by the shags. Small nototheniid fish (c. 10 kJ per item) were by far the commonest prey but most pellets contained additional items. The frequency of pellets with additional items of higher energy value than nototheniid fish (10.c. 900 kJ per item), lower energy value (>1–10 kJ per item) and both higher and lower energy items was strikingly similar to the frequency of shags making long, short and both long and short dives respectively. Predicted aerobic dive limits suggested that during long dives, blue-eyed shags were probably sustained by anaerobic metabolism. Models of prey capture rates demonstrated that for both long and short diving, many items must be caught per dive when birds are feeding on prey at the lower end of the energy range. Predicted capture rates for the commonest recorded prey (small fish) differ markedly between the two diving strategies.     

Geographical variation in morphometry of black-browed and grey-headed albatrosses from four sites

Differences in morphometry between five populations of black-browed albatrosses (Diomedea melanophrys) and four populations of grey-headed albatrosses (D. chrysostoma) are examined. Two clear groups of black-browed albatrosses are evident, with birds from the subspecies Diomedea melanophrys impavida showing significant differences in several variables from those from the subspecies Diomedea melanophrys melanophrys. For groups from the latter subspecies, birds from South Georgia had larger measures than those from Kerguelen. A similar pattern to that of Diomedea melanophrys melanophrys was found between the groups of grey-headed albatrosses. Analysis of foraging distances relative to adult body-size index and the duration of chick-rearing periods suggests that differences in chick-provisioning rates between populations of conspecifics could account for at least some of the observed differences in adult morphometry. Accepted: 5 April 1999     

The diet of black-browed albatrosses at the Diego Ramirez Islands,Chile

The diet of black-browed albatrosses was studied at Gonzalo Island, Diego Ramirez, Chile, during the early chick-rearing periods of 2000, 2001, and 2002. Diet composition was determined by sampling chick-stomach contents during January and February of each year. Reconstituted meal mass was similar throughout the study, with diet being dominated by fish in all 3 years. Overall, the main items taken were the fishes Macruronus magellanicus (66–89% by mass) and Micromesistius australis (2.6–3.7% by mass), which are both fisheries-related species, and the squid Martialia hyadesi (8–20% by mass). The distribution of the prey species indicates that black-browed albatrosses obtained the bulk of their food over the South American continental shelf, but also foraged at the Antarctic Polar Front. The prevalence in the diet of fish species discarded from fishing operations, and the presence of fish hooks and fish bait species, indicate a strong association with fisheries in southern Chile.     

The diet of Antarctic fur sealsArctocephalus gazella during the breeding season at South Georgia

 The diet of lactating female Antarctic fur seals Arctocephalus gazella at South Georgia was investigated during the pup-rearing period (January/March) of 1991–1994. Antarctic krill Euphausia superba was the main prey item, occurring in 88% of all scats (n=497), whereas fish occurred in 47% and squid in 5% of all scats. There was considerable intra- and inter-annual variation in the characteristics of krill taken by fur seals. The distribution of krill sizes taken suggests that fur seals are not actively selecting particular sizes of krill and, therefore, that the krill in the diet reflects the krill available around South Georgia. The absence of group 3 krill (44–48 mm in length) in the South Georgia area, as indicated by their absence in the diet of seals, is suggested as a possible reason for low availability of krill and the subsequent reproductive failure among krill predators. The frequency of occurrence of fish was much higher than in previous studies; the pattern of fish consumption showed a consistent seasonal pattern in 3 of the 4 years studied. Of the total number of the myctophid Protomyctophum choriodon, the most numerous fish taxon, 98% were taken between early February and the middle of March. Champsocephalus gunnari and Lepidonotothen larseni agg., which both feed on krill, dominated the fish component of the diet outside this period and together constituted 94% of the total estimated biomass of fish consumed. The intra- and inter-annual variability in the diet of Antarctic fur seals emphasise the need for diet studies to be conducted during the entire pup-rearing periods of several years. Received: 15 March 1995/Accepted: 13 May 1995     

The diet of the South Georgia shag Phalacrocorax georgianus at South Orkney Islands in five consecutive years

The diet of the South Georgia shag Phalacrocorax georgianus at Laurie Island, South Orkney Islands, was studied by the analysis of 420 pellets (regurgitated casts) collected from the 1995 to 1999 breeding seasons. Demersal-benthic fish were by far the main prey, followed by molluscs (mainly octopods and bivalves) and polychaetes. Harpagifer antarcticus (in 1995, 1998, 1999) and Lepidonotothen nudifrons (1996, 1997) were the most frequent prey, followed by Gobionotothen gibberifrons or Trematomus newnesi. Harpagifer antarcticus, followed by L. nudifrons or T. newnesi, was the most numerous prey in all of the seasons and predominated in mass in 1995 and 1996, followed by Notothenia coriiceps and L. nudifrons. In 1997 and 1999, G. gibberifrons and N. coriiceps were the species that most contributed to the diet whereas N. coriiceps and H. antarcticus contributed most in 1998. Our results differ from those reported for the South Orkney Islands in previous studies. These differences could be due to the use of different diet-analysis methods and to shags-related and/or fisheries-related changes in the food availability around the colonies. These alternative explanations are analysed and discussed.     

Electrophoretic analysis of Antarctic fish from South Georgia

White muscle samples of Antarctic fish (Notothenia rossii, N. neglecta, N. gibberifrons and Chaenocephalus aceratus) were subjected to electrophoretic tests. Isoelectric focusing of general muscle proteins provides a quick method of identifying species. Six muscle enzymes were resolved by horizontal starch gel electrophoresis. These are presumed to be the products of ten independent gene loci. Coefficients of genetic distance were calculated and substantially agree with the conventional taxonomy. Levels of genetic variability are within the normal range for marine teleosts. Two polymorphic enzymes. GPI and PGM, might prove useful as 'genetic tags' for stock identification.     

Electrophoretic analysis of Antarctic fish from South Georgia

White muscle samples of Antarctic fish ( Notothenia rossii, N., neglecta. N. gibbe-rifrons and Chaenocephalus (aceratus ) were subjected to electrophoretic tests. lsoelectric focusing of general muscle proteins provides a quick method of iden-tyfying species. Six muscle enzymes were resolved by horizontal starch gel clectrophoresis. These are presumed to be the products of ten independent gene loci. Coefficients of genetic distance were calculated and substantially agree with the conventional taxnomy. Levels of genetic variability are within the normal range for marine teleosts. Two polymorphic enzymes. GPI and PGM. might prove useful as 'genetic tags' for stock identification.     

Differences in the timing and extent of annual moult of black-browed albatrosses Thalassarche melanophris living in contrasting environments

Moult entails costs related to the acquisition of energy and nutrients necessary for feather synthesis, as well as the impact of reduced flight performance induced by gaps in the wing plumage. Variation in moult strategies within and between populations may convey valuable information on energetic trade-offs and other responses to differing environmental constraints. We studied the moult strategies of two populations of a pelagic seabird, the black-browed albatross Thalassarche melanophris, nesting in contrasting environments. According to conventional wisdom, it is exceptional for albatrosses (Diomedeidae) to moult while breeding. Here we show that black-browed albatrosses breeding on the Falklands regularly moult primaries, tail and body feathers during chick-rearing, and the majority of those at South Georgia show some body feather moult in late chick-rearing. The greater moult-breeding overlap at the Falklands allows the birds to annually renew more primary feathers than their counterparts at South Georgia. The results of the present paper, pooled with other evidence, suggest that black-browed albatrosses from South Georgia face a more challenging environment during reproduction. They also serve to warn against the uncritical acceptance of conventional ideas about moult patterns when using feathers to study the ecology of seabirds and other migrants for which there is scant information at particular stages of the annual cycle.     

The breeding biology of the white-chinned petrel Procellaria aequinoctialis at South Georgia

Aspects of the breeding biology of the whitc-chinned petrel Procellaria aequinoctialis were studied at South Georgia. Laying, hatching and fledging dates, together with egg and adult measurements, rate of weight loss of eggs and incubating adults and data on the duration of incubation shifts were recorded. Chick growth in weight, tarsus length, culmen length and wing length from hatching to fledging was followed in detail and breeding success and causes of mortality documented. Comparisons are made with other populations of the species, other members of the genus Procellaria and other Procellariiformes. Despite being the largest burrow-nesting petrel in the world, P. aequinoctialis conforms well to the overall relationships between body weight and breeding parameters for Procellariiformes in general.     

Moult of the giant petrels Macronectes halli and M. giganteus at South Georgia

Moult scores were collected from colour-ringed individuals of known reproductive status of the two species of giant petrel, Macronectes halli and M. giganteus , at Bird Island, South Georgia between 1978–81.
Both species showed a substantial overlap between breeding and wing-moult, unlike most other Southern Ocean seabirds. Males started moult before females and both sexes of M. giganteus moulted at an earlier stage of the breeding cycle than M. halli , which breeds six weeks earlier than its congener.
Changes in moult rate during the breeding season are documented for both species, with Id. halli showing a rapid increase as the chick nears fledging. Male M. giganteus show a notably different pattern to the other three species-sex groups, starting moult much earlier (at egg-laying), with greater individual synchrony and usually suspending primary moult throughout the main chick growth period, whereas only two male M. halli and no females of either species suspended moult. Differences in pattern, timing and rate of moult are interpreted in terms of availability of food resources and the competing energy demands of other activities, especially chick-rearing.
Completion of primary moult could not be observed in the field but was estimated using data frcsm non-breeding birds and failed breeders; the latter started a rapid moult almost immediately they failed. In both sexes of both species moult is probably concluded at least by early winter.
The general pattern of moult in giant petrels at Bird Island is contrasted with that of other populations and species of Southern Ocean seabirds. It is suggested that the unusually extensive overlap between breeding and moult in giant petrels is a consequence of the very abundant and easily available summer food supplies (especially carrion) and the much diminished winter resources, favouring a completion of moult by the beginning of the winter.     

The food and feeding ecology of the giant petrels Macronectes halli and M. giganteus at South Georgia

Giant petrels are the chief scavenging seabirds in the Southern Ocean. Quantitatively analysed regurgitations from chicks of both Macronectes halli and M. giganteus at Bird Island, South Georgia throughout the chick rearing period consisted predominantly of adult Macaroni penguins Eudyptes chrysolophus. Significant quantities of burrowing petrels and krill were taken but the amount varied in different years. Only male M. halli fed regularly at fur seal carcases. Although 10 species were found in regurgitations, squid were unimportant in the diet. Fish are possibly more important during the winter.
Intersexual differences in diet were of greater significance than interspecific ones with males taking more carrion and females more crustaceans. Chicks were fed during both day and night and in both species males received significantly more food than females during the fledging period. M. giganteus chicks received more than M. halli at all ages.
Despite their extensive reliance on carrion both species take a variety of prey and this may be especially important during the winter when penguin and seal carrion is scarce.     

The terrestrial Protozoan fauna of South Georgia

Summary 75 taxa of Protozoa (18 flagellates, 9 naked rhizopods, 20 testate rhizopods and 28 ciliates) were found in 14 samples of mineral materials, peats, soils and guano collected from the sub-Antarctic island of South Georgia. The results confirm the existence of distinct natural communities of protozoan species related to the different classes of habitat in the sub-Antarctic and maritime Antarctic, but suggest that species characteristic of the maritime Antarctic also occur in the sub-Antarctic and species characteristic of bryophyte peats also occur in soils with angiosperm vegetation. The diversity of the fauna of different habitats can be related to degree of soil development and successional stage of associated vegetation. Comparison of the data on the testate rhizopod fauna of South Georgia with those from other sub-Antarctic locations shows a clear trend of faunal pauperization with latitude.     

The summer zooplankton community at South Georgia: biomass,vertical migration and grazing

Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m^–2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times higher than values generally reported for the Southern Ocean and may reflect firstly, the high productivity of the study area, secondly, the time of year, summer, when biomass for many species is maximal, and thirdly, the high sampling efficiency of the LHPR. Principal components analysis disclosed similarities and differences between adjacent depth strata in terms of abundance, biomass and species composition. At both stations most variability occurred in the mixed layer (0–60 m) and thermocline (60–120 m) with depth horizons below this being more homogeneous. Diel migrations were observed for most taxa with abundance increasing in the mixed layer at night. At the oceanic station, species and higher taxa belonging to the mesopelagic community were generally well spread throughout this domain and, with the exception of Pleuromamma robusta and Metridia curticauda, showed little evidence of migration. The grazing impact of the epipelagic community (copepods and small euphausiids) was estimated to remove 3–4% of the microbial standing stock day^–1 and a conservative 25% and 56% of daily primary production at the oceanic and shelf stations respectively.