Foraging interactions between Wandering Albatrosses Diomedea exulans breeding on Marion Island and long-line fisheries in the southern Indian Ocean

Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.     

Distribution, abundance and behaviour of Buller's, Chatham Island and Salvin's Albatrosses off Chile and Peru

During 15 cruises between 1980 and 1995, we studied three species of albatross that nest in New Zealand but occur as non‐breeders along the Pacific coast of South America: Buller's Thalassarche bulleri, Chatham Island T. eremita, and Salvin's Albatross T. salvini. We logged 547 h of observation, surveying 7638 km² of ocean surface, and recorded 86, 27, and 475 individuals, respectively, of the three species. Chatham Island and Salvin's Albatrosses occurred throughout the Humboldt Current, but habitats differed. Buller's and Salvin's Albatrosses preferred the continental slope, while Chatham Island Albatrosses frequented mostly pelagic waters. On a latitudinal basis, Salvin's Albatross distribution was skewed northward in the austral autumn and southward in spring; Chatham Island Albatross occurred southward during autumn, but was everywhere scarce in spring; and Buller's Albatross occurred almost exclusively in the south (30°S to 40°S) in both seasons. Upwelling and wind speed were positively correlated with densities of Buller's and Salvin's Albatrosses. Densities of Chatham Island Albatrosses also were positively correlated with wind speed, but they occurred further offshore in more stratified waters (with less mixing/upwelling) than did the other two. Pelagic population estimates for the Humboldt Current system, analysed using generalized additive models, peaked at 26 700 individuals for Buller's Albatross (95% confidence interval (CI) 13 100–37 100); 6790 for Chatham Island Albatross (CI 3900–11 100); and 133 100 for Salvin's Albatross (CI 82 800–183 600). Based on adult:subadult ratios observed in the study area, our best estimates for the number of wintering adults were 9100, 5800 and 114 400 birds, respectively, or 20%, 73% and 75% of the numbers estimated (44 500, 8000 and 153 300 birds) for the breeding populations at respective colonies. If we subtract from the autumn count the number of adult‐plumaged birds seen in spring (assumed to be non‐breeders), then respective percentages were 0%, 73% and 65%. Foraging locations and attraction by these birds to commercial fishing operations makes them susceptible to mortality as a result of the recent development of a long‐line fishery on the continental slope of Chile.     

Longline Fisheries and Foraging Distribution of Flesh-Footed Shearwaters in Eastern Australia

ABSTRACT Incidental seabird mortality associated with bycatch during longline commercial fishing is a conservation concern. An initial step to estimating likelihood of seabird bycatch and conceiving conservation strategies is determining amount of overlap between foraging birds and commercial fishing effort, identifying oceanographic features associated with foraging birds, and quantifying dive characteristics. We tracked 24 adult flesh-footed shearwaters (Puffinus carneipes) breeding on Lord Howe Island located east of Australia during incubation and early and late chick-rearing periods from 6 January to 17 April 2005. At-sea foraging distribution of flesh-footed shearwaters was primarily confined within the jurisdictional Australian Fishing Zone. Foraging was strongly associated with sea-surface temperature >24°C. Spatial and temporal overlap of longline fishing with foraging shearwaters varied throughout the breeding season, but was greatest (63% overlap) during early chick-rearing. Mean maximum distance reached from the breeding colony during a foraging event was 804 km (SD = 280) from Lord Howe Island. Foraging behavior was strongly diurnal, with 91% of dives occurring during daylight, and most dives (77%) were <5 m. Given that longline fishing and flesh-footed shearwaters overlap substantially, the Australian Fisheries Management Authority should consider implementing additional regulations to further reduce bycatch. Conservation strategies such as setting longlines at nights may reduce flesh-footed shearwater bycatch.     

Population dynamics of Black-browed and Grey-headed Albatrosses Diomedea melanophrys and D. chrysostoma at Campbell Island, New Zealand, 1942–96

The numbers of Black-browed Albatrosses Diomedea melanophrys and Grey-headed Albatrosses D. chrysostoma at Campbell Island, New Zealand, have declined dramatically since the 1940s. Black-browed Albatross numbers went into a steep decline in the 1970s and, since at least 1984, have been increasing slightly at average rates of 1.1% and 2.1% per annum at two colonies. The long-term downward trend in numbers of the Grey-headed Albatross has continued into the 1990s, averaging annually between 3.0% and 4.8% per annum at different colonies. A demographic study carried out between 1984 and 1996 indicates that Black-browed and Grey-headed Albatrosses have similarly high annual adult survival rates (0.945 and 0.953, respectively). Black-browed Albatrosses breed for the first time at a younger average age than do Grey-headed Albatrosses (10 years and 13.5 years, respectively), have a higher average breeding success (0.663 compared with 0.397 for the latter species) and are annual breeders whereas Greyheaded Albatross show a typical biennial pattern of breeding. Both show low survival from fledging to first breeding; averaging 0.186 and 0.162 for Black-browed and Grey-headed Albatrosses, respectively. Both species are accidentally killed in the Japanese long-line fishery for tuna Thunnus sp. in the Australasian region. The steep decline of Black-browed Albatross numbers in the 1970s was concomitant with the development of this fishery in the foraging region of the Campbell Island birds. Currently, the slight increase in numbers is due to high adult survival rates and breeding success, and is coincident with a great reduction in long-line fishing. With stable and high adult survival rates, it is expected that future population trends will be mainly influenced by the recruitment rates. The continuous decline in Grey-headed Albatross numbers since the 1940s, before long-line fishing developed in this region, indicates that natural environmental processes contributed to the downward trend in breeding numbers. Modelling indicates that Grey-headed Albatross numbers will continue to decrease with the present demographic parameters. A comparison between the species breeding at different sites shows that differing environmental conditions influence demographic characteristics.     

REVIEWS AND RECORDS

Summerhayes, C. P., Hofmeyr. P. K. &; Rioux, R. H. 1974. Seabirds off the southwestern coast of Africa. Ostrich 45: 83–109.

The distribution of seabirds off the southwestern coast of Africa was observed during April. May and November, and observed south of Africa in March. Most seabirds off the west coast were concentrated near to the coast or over the edge of the continental shelf. These are sites where forms of upwelling bring water rich in nutrients to the surface of the sea. The most birds were seen in March, April and May, the least in November. Most common over the shelf-edge were, in order of abundance, Blackbrowed Albatross, Cape Hens, Shy Albatross, Yellownosed Albatross, Wilson's Storm Petrels, Cape Gannets, Common/Arctic Terns, and Antarctic Skuas. Seasonal shifts in their ranges and population densities probably reflect the influence of breeding and migration.

Comparable concentrations of seabirds were only seen as the cold, nutrient-rich waters of the Subantarctic were approached south of Africa. Here turbulence breaks up the front of the Subtropical Convergence and, in moving large masses of cold water northwards, provides a “corridor” which Southern Ocean species may follow to reach Africa.

(Contribution No. 2687 of the Woods Hole Oceanographic Institution).     

Effects of Climate Change and Fisheries Bycatch on Shy Albatross (Thalassarche cauta) in Southern Australia

The impacts of climate change on marine species are often compounded by other stressors that make direct attribution and prediction difficult. Shy albatrosses (Thalassarche cauta) breeding on Albatross Island, Tasmania, show an unusually restricted foraging range, allowing easier discrimination between the influence of non-climate stressors (fisheries bycatch) and environmental variation. Local environmental conditions (rainfall, air temperature, and sea-surface height, an indicator of upwelling) during the vulnerable chick-rearing stage, have been correlated with breeding success of shy albatrosses. We use an age-, stage- and sex-structured population model to explore potential relationships between local environmental factors and albatross breeding success while accounting for fisheries bycatch by trawl and longline fisheries. The model uses time-series of observed breeding population counts, breeding success, adult and juvenile survival rates and a bycatch mortality observation for trawl fishing to estimate fisheries catchability, environmental influence, natural mortality rate, density dependence, and productivity. Observed at-sea distributions for adult and juvenile birds were coupled with reported fishing effort to estimate vulnerability to incidental bycatch. The inclusion of rainfall, temperature and sea-surface height as explanatory variables for annual chick mortality rate was statistically significant. Global climate models predict little change in future local average rainfall, however, increases are forecast in both temperatures and upwelling, which are predicted to have detrimental and beneficial effects, respectively, on breeding success. The model shows that mitigation of at least 50% of present bycatch is required to offset losses due to future temperature changes, even if upwelling increases substantially. Our results highlight the benefits of using an integrated modeling approach, which uses available demographic as well as environmental data within a single estimation framework, to provide future predictions. Such predictions inform the development of management options in the face of climate change.     

Diving behaviour of the Shy Albatross Diomedea cauta in Tasmania: initial findings and dive recorder assessment

The diving behaviour of the Shy Albatross Diomedea cauta was investigated using archival time-depth recorders (TDRs) and maximum depth gauges (MDGs). Data from birds carrying multiple devices and from diving simulations indicated that the degree of correspondence between TDRs and MDGs varied with the dive depth, duration and frequency, as well as with body placement. The MDGs were the most reliable when the diving depth was greater than 0.5 m, when the diving frequency was low and when gauges were placed on the birds' backs. The TDRs were used during late incubation and early chick rearing in 1994. Fifty-two dives (0.4 m) were recorded during 20 foraging trips of 15 individuals. The majority of dives were within the upper 3 m of the water column and lasted for less than 6 s. However, dives to 7.4 m and others lasting 19 s were recorded. The albatrosses dived between 07.00 h and 22.00 h, with peaks in their diving activity near midday and twilight. Mean diving depth varied throughout the day. with the deepest dives occurring between 10.00 h and 12.00 h. Two dive types were identified on the basis of the relationship between dive depth and descent rate. Plunge dives were short (5 s), and the birds reached a maximum depth of 2.9 m. Swimming dives were both longer and deeper. The characteristics of Shy Albatross plunge dives were similar to those of gannets Morus spp., which are known to be proficient plunge divers. Swimming dives suggest that Shy Albatrosses actively pursue prey underwater.     

Combined impacts of longline fisheries and climate on the persistence of the Amsterdam Albatross Diomedia amsterdamensis

Incidental capture of seabirds in longline fishing gear is a central issue in the conservation of many long-lived marine species. Despite growing evidence of climate-induced effects on population trends of long-lived species, climate change remains generally overlooked in most risk assessments of seabirds. Because variation in climate may interact with the detrimental effects of bycatch, considering climate is of great importance, especially in the context of ongoing global warming. This paper examines the combined effects of bycatch and climate change on the persistence of one of the world's rarest birds, the Amsterdam Albatross Diomedea amsterdamensis , which has a single population in the upland plateau of Amsterdam Island (Southeast Indian Ocean). Using continuous monitoring from 1983 onwards, we first estimated the relationship between climate and the species' demographic parameters. We then built a stochastic matrix population model to estimate the population growth rate and the probability that the population declines below the level recorded in 1983 of nine breeding pairs under different scenarios involving the joint effects of additional mortality caused by longline fisheries and climate change. The results suggest that the demography of the Amsterdam Albatross is influenced by climate in both breeding and wintering grounds and that these relationships may to some extent compensate for the impact of additive bycatch mortality. However, these compensatory effects would be negligible if the annual additional mortality exceeds around six individuals per year, suggesting that the resumption of longline fishery in the foraging range of the Amsterdam Albatross would rapidly put this species at risk of extinction.     

Interannual variation in the diets of two albatross species breeding at South Georgia: implications for breeding performance

The diet and breeding performance of Grey‐headed Albatrosses Thalassarche chrysostoma and Black‐browed Albatrosses Diomedea melanophris breeding at Bird Island, South Georgia, were studied simultaneously during the chick‐rearing period between 1996 and 2000. When samples for all years were combined, cephalopods and crustaceans were the main components in the diet of Grey‐headed and Black‐browed Albatrosses, respectively. However, their diets exhibited interannual variations. Cephalopods were the most important component in the diet of Grey‐headed Albatrosses between 1996 and 1999 (60–75% by mass) but decreased significantly in 2000 (17%), when crustaceans dominated (61%). The Black‐browed Albatross diet varied greatly, with cephalopods being the most important component in 1996 (49% by mass) and 1997 (48%), fish in 1998 (32%) and 1999 (40%), and crustaceans in 2000 (63%). In 1998 and 2000 there was a significant change in the cephalopod species present in the diet of both albatross species, when their breeding success was low. The consumption of the ommastrephid Martialia hyadesi was significantly and positively correlated with Grey‐headed Albatross breeding success. For Black‐browed Albatrosses significant correlations were found between its consumption of the Icefish Champsocephalus gunnari and breeding success, and between its consumption of M. hyadesi and M. hyadesi CPUE (Catch per Unit Effort). These findings suggest that Grey‐headed Albatrosses are more reliant on Antarctic Polar Frontal Zone prey (M. hyadesi and Lamprey Geotria australis) whereas Black‐browed Albatrosses are more dependent on Antarctic prey (Icefish and Antarctic Krill Euphausia superba). The differences between diets of Grey‐headed and Black‐browed Albatrosses breeding on different islands of the Southern Ocean showed that Grey‐headed Albatrosses feed more on oceanic cephalopods (e.g. M. hyadesi) whereas Black‐browed Albatrosses feed primarily on shelf fish (e.g. Blue Whiting Micromesistius australis), suggesting that albatross diets are likely to be influenced by the geographical position of those islands, albatross foraging preference and prey availability.     

Chick provisioning rates and growth in Blacklbrowed Albatross Diomedea melanophris and Grey-headed Albatross D. chrysostoma at Bird Island, South Georgia

We compared the parental division of labour and the pattern and rate of parental provisioning by two sympatric species of albatross of similar mass and breeding timetable but differing in diet and in the duration of chick‐rearing. Using electronic weighing platforms inside artificial nests, we recorded chick mass of Black‐browed Albatross and Grey‐headed Albatross at Bird Island, South Georgia every 10 minutes for both species in 1993 and 1994 and for each species in two other years between 1990 and 1996. The chick mass data (nearly one million weighings) were used to calculate meal mass (over 5000 meals) and intervals between meals. Adult birds were fitted with radio‐transmitters which allowed each meal to be allocated to the appropriate parent. The combination of meal mass and foraging trip duration were used to calculate provisioning rates for chicks and individual adults. Overall, Black‐browed Albatrosses delivered significantly lighter meals (569 g) than Grey‐headed Albatrosses (616 g) but more frequently (every 2.07 days and 2.50 days respectively). Thus combining foraging trip data for both parents, Black‐browed Albatross chicks received a meal every 1.22 days compared with 1.26 days for Greyheaded Albatross. These rates did not differ significantly. The contribution of each sex of each species in chick provisioning fluctuated between years, being similar in some years or biased towards males in others. Chicks of both species that failed to fledge received smaller, less frequent meals than successful chicks. In 1990 and 1994, Black‐browed Albatross chick provisioning rates were lower than in 1992 and 1993. In 1990, both meal mass and trip duration were affected, but only in 1994 was trip duration longer. Greyheaded Albatross chick provisioning rate was lower in 1994 than in other years but trip duration was longer. In each species, significant changes in meal mass and trip duration occurred within the chick‐rearing period. Chick provisioning rates invariably declined before chicks attained their peak mass. For both species, chick growth rates and peak and fledging mass, but not fledging age, were affected by differences in provisioning rate.     

Seabirds attending bottom long-line fishing off southeastern Brazil

Flocks of seabirds attending commercial bottom long-line fishing operations on the coastal shelf off southeastern Brazil show a greater species diversity during the summer than the winter (16 v 9 species), although the number of birds per flock tended to be greater during the cold season. During the summer, the Spectacled Petrel Procellaria aequinoctialis conspi-cillata was the commonest species, followed by the Great Shearwater Puffinus gravis, Cory's Shearwater Calonectris diomedea, skuas Stercorarius spp. and the Yellow-nosed Albatross Diomedea chlororhynchus. During the winter, the White-chinned Petrel Procellaria aequin-octialis, Yellow-nosed Albatross and Black-browed Albatross Diomedea melanophrys were jointly the commonest species. Marked differences in the relative abundance of species were observed between the different sampling periods, probably because of migratory movements but also because of seasonal shifts of the sea currents and the influence of cold fronts. Waters off southeastern Brazil are important feeding areas for some seabird populations nesting in the Tristan da Cunha and Gough group, especially for nonbreeding Spectacled Petrels and post-breeding Yellow-nosed Albatrosses.     

Satellite tracking of light-mantled sooty albatrosses

Five light-mantled sooty albatrosses (Phoebetria palpebrata) breeding at Macquarie Island were tracked with miniaturised satellite transmitters during foraging trips of the incubation period. Birds moved rapidly to specific sectors of the Southern Ocean, where they spent several days foraging before returning to their nests. These specific sectors were at an average distance of 1516 km from Macquarie Island and located in pelagic Antarctic waters, mostly along the Antarctic continent. The maximum foraging range was in average 1721 km and the total distance covered by two birds for which there were complete tracks was 6463 and 6975 km. This study confirms previous suggestions that light-mantled sooty albatrosses are able to forage in the waters of the high Antarctic while breeding in the sub-Antarctic. The implications of the extreme separation of feeding zones from nesting grounds, in terms of conservation and life-history strategies, are discussed.     

Individual foraging site fidelity in lactating New Zealand fur seals: Continental shelf vs. oceanic habitats

Wide‐ranging marine central place foragers often exhibit foraging site fidelity to oceanographic features over differing spatial scales (i.e., localized coastal upwellings and oceanic fronts). Few studies have tested how the degree of site fidelity to foraging areas varies in relation to the type of ocean features used. In order to determine how foraging site fidelity varied between continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur seals (Arctocephalus australis forsteri 1 ) were satellite tracked over consecutive foraging trips (14–108 d). Thirty‐seven foraging trips were recorded from 11 females that foraged on the continental shelf, in a region associated with a coastal upwelling, while 65 foraging trips were recorded from 20 females that foraged in oceanic waters. There were no significant differences in the mean bearings (to maximum distance) of individual's consecutive foraging trips, suggesting individual fidelity to foraging areas. However, overlap in area and time spent in area varied considerably between continental shelf and oceanic foragers. Females that foraged on the continental shelf had significantly greater overlap in consecutive foraging trips when compared to females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited on consecutive trips 55.9%± 20.4% and 13.4%± 7.6%, respectively). Females that foraged on the continental shelf also spent significantly more time within the same grid cell than females that foraged in oceanic waters (maximum time spent in 5 × 5 km grid cells: 14%± 5% and 4%± 2%, respectively). This comparatively high foraging site fidelity may reflect the concentration of productivity associated with a coastal upwelling system, the Bonney Upwelling. Lower foraging site fidelity recorded by seals that foraged in oceanic waters implies a lower density/larger scale habitat, where prey are more dispersed or less predictable at fine scales, when compared to the continental shelf region.     

Distribution and movements of Buller's albatross (Diomedea bulleri) in Australasian seas

Abstract

The distribution and movements of Buller's albatross in Australasian seas are analysed using results of shipborne surveys (13 238 10‐min counts), counts from trawlers, banding data, recoveries on beaches and fishing vessels, and records from the literature. Patterns of marine distribution are documented by monthly accounts and maps. During the breeding season, highest abundances are recorded over shelves and slopes off southern New Zealand (The Snares shelf to 41–43°S off the South Island, D. b. bulleri), around the Chatham Islands and over oceanic subtropical waters east of New Zealand (probably D. b. platei), with marked seasonal variations observed off southern New Zealand. Both subspecies disperse mostly outside Australasian waters during the non‐breeding season. Birds banded on The Snares were recovered off south‐eastern New Zealand (Stewart Island to Cook Strait) and in the eastern tropical Pacific. Immatures accounted for only 0.25% of birds censused during the ship‐borne surveys; they are recorded around the New Zealand mainland in August‐October and February‐May, off south‐eastern Australia and in the Tasman Sea in November‐December, February, and June‐July. Around New Zealand, males predominate among birds recovered along the eastern seaboard, whereas the sex ratio in south‐western waters tends to vary according to water depth and season. Distribution patterns and movements in New Zealand and Australian seas are discussed in relation to breeding events and breeding status.     

THE FOOD AND FEEDING ECOLOGY OF GREY-HEADED ALBATROSS DIOMEDEA CHRYSOSTOMA AND BLACK-BROWED ALBATROSS D. MELANOPHRIS

The food and feeding ecology of Black-browed Albatrosses and Grey-headed Albatrosses was studied from 1975 to 1978 at Bird Island, South Georgia. Two hundred and seventy food samples (averaging 75–85 % by weight of the mean chick feed) were collected from adults of each species in February and March. Chicks of both species received meals of the same size, of which half consisted of liquid. The three major components of the solid diet (krill, squid and fish) were similar for both albatrosses. By weight, fish represented about 35 % of the diet of both species; squid predominated (50 %) in the diet of Grey-headed Albatross, and krill (40 %) in the diet of Black-browed Albatross. Lampreys were confined to the Grey-headed Albatross and, although squid of similar sizes were taken by both species, Black-browed Albatrosses took a much greater diversity of squid. Each major prey type was associated with a characteristic amount of liquid in the complete samples and only in the case of krill and lamprey was this lipid-rich.
As these two albatrosses are of similar size, breed over the same period and feed meals of equivalent weight to their chicks at similar intervals, the difference in the composition of the diet is possibly the most significant mechanism of ecological segregation (in the breeding season).
Evidence of the effect of krill shortage in drastically reducing Black-browed Albatross breeding success is presented to support this. The two species have largely non-overlapping winter oceanic ranges which are probably also correlated with the distribution of preferred prey.     

Breeding frequency in Grey-headed Albatrosses Thalassarche chrysostoma

Although Grey-headed Albatrosses Thalassarche chrysostoma are usually regarded as biennial breeders, taking a year off following a successful breeding attempt, a small proportion of successful birds attempt to breed annually. This proportion was higher at Marion Island (5.4%) than at Bird Island, South Georgia (1.0%), suggesting that conditions are more favourable at Marion Island. This hypothesis is supported by higher average breeding success and shorter lags following both successful and failed breeding attempts at Marion Island. Factors favouring reproduction at Marion Island may include reduced intraspecific competition (given the much smaller breeding population) and/or more predictable food supply (owing to production of meso-scale eddies associated with the Indian Ocean Ridge). Although annual breeding appeared to increase the risk of adult mortality, with several birds that attempted to breed annually found dead the following year, at least some birds greatly enhanced their reproductive output, with one male raising five chicks in five successive years. Contrary to life-history theory, there was no evidence that older birds were more likely to attempt annual breeding because of declining reproductive value.     

Intra-seasonal variation in foraging behavior among Ad��lie penguins (Pygocelis adeliae) breeding at Cape Hallett, Ross Sea, Antarctica

We investigated intra-seasonal variation in foraging behavior of chick-rearing Adélie penguins, Pygoscelis adeliae, during two consecutive summers at Cape Hallett, northwestern Ross Sea. Although foraging behavior of this species has been extensively studied throughout the broad continental shelf region of the Ross Sea, this is the first study to report foraging behaviors and habitat affiliations among birds occupying continental slope waters. Continental slope habitat supports the greatest abundances of this species throughout its range, but we lack information about how intra-specific competition for prey might affect foraging and at-sea distribution and how these attributes compare with previous Ross Sea studies. Foraging trips increased in both distance and duration as breeding advanced from guard to crèche stage, but foraging dive depth, dive rates, and vertical dive distances travelled per hour decreased. Consistent with previous studies within slope habitats elsewhere in Antarctic waters, Antarctic krill (Euphausia superba) dominated chick meal composition, but fish increased four-fold from guard to crèche stages. Foraging-, focal-, and core areas all doubled during the crèche stage as individuals shifted distribution in a southeasterly direction away from the coast while simultaneously becoming more widely dispersed (i.e., less spatial overlap among individuals). Intra-specific competition for prey among Adélie penguins appears to influence foraging behavior of this species, even in food webs dominated by Antarctic krill.     

Comparative activity pattern during foraging of four albatross species

The activity patterns of foraging Yellow‐nosed Diomedea chlororhynchos, Sooty Phoebetria fusca, Black‐browed D. melanophris impavida and Grey‐headed Albatross D. chrysostoma were compared using loggers recording the timing of landing and take‐offs, as well as the duration of bouts in flight or on the water, and the overall time spent in flight. The four species spent a similar proportion of their foraging time in flight (56–65%). During the day they were mostly flying (77–85% of the daylight period) whereas at night they were mainly (61–71%) sitting on the water. The amount of time spent in flight during the daytime foraging period was related to the amount of time spent sitting on the water at night. Differences between species occurred in the duration of bouts in flight and on the water as well as in the frequency of landings and in the time elapsed between successive landings. Yellow‐nosed Albatrosses were more active than the other species, with more frequent short bouts in flight and more frequent successive landings at short intervals. Sooty Albatrosses landed or took‐off less often than the other species and were more active just before dusk. Black‐browed and Grey‐headed Albatrosses were more active at night, especially the first part of the night and far from the colonies. Their trips consisted of a commuting part and a foraging part. Black‐browed Albatrosses landed more often during the foraging than the commuting part, suggesting that they were not searching when travelling. The study suggests that there is no fundamental difference between the overall activity budgets of the four species although they show distinctive diet, morphology and life history traits. The differences observed between the four species were related mainly to differences in foraging technique. Comparison with the Wandering Albatross, the only species for which data were available previously, suggest that this larger species might differ completely in foraging technique from the smaller albatrosses.     

Factors determining nest-site selection of surface-nesting seabirds: a case study on the world's largest pelagic bird,the Wandering Albatross (Diomedea exulans)

Several factors may drive bird nest-site selection, including predation risk, resource availability, weather conditions and interaction with other individuals. Understanding the drivers affecting where birds nest is important for conservation planning, especially where environmental change may alter the distribution of suitable nest-sites. This study investigates which environmental variables affect nest-site selection by the Wandering Albatross Diomedea exulans, the world's largest pelagic bird. Here, wind characteristics are quantitatively investigated as a driver of nest-site selection in surface-nesting birds, in addition to several topographical variables, vegetation and geological characteristics. Nest locations from three different breeding seasons on sub-Antarctic Marion Island were modelled to assess which environmental factors affect nest-site selection. Elevation was the most important determinant of nest-site selection, with Wandering Albatrosses only nesting at low elevations. Distance from the coast and terrain roughness were also important predictors, with nests more generally found close to the coast and in flatter terrain, followed by wind velocity, which showed a hump-shaped relationship with the probability of nest occurrence. Nests occurred more frequently on coastal vegetation types, and were absent from polar desert vegetation (generally above c. 500 m elevation). Of the variables that influence Wandering Albatross nest location, both vegetation type and wind characteristics are likely to be influenced by climate change, and have already changed over the last 50 years. As a result, the availability of suitable nest-sites needs to be considered in light of future climate change, in addition to the impacts that these changes will have on foraging patterns and prey distribution. More broadly, these results provide insights into how a wide range of environmental variables, including wind, can affect nest-site selection of surface-nesting seabirds.     

Foraging grounds of southern giant petrels (<Emphasis Type="Italic">Macronectes giganteus</Emphasis>) on the Patagonian shelf

During the 1999 and 2000 breeding seasons we used satellite telemetry to track the foraging movements of four southern giant petrels (Macronectes giganteus) nesting on an island off the Argentine coast (45°08', 66°03'). Three of the four individuals foraged east/southeast of the colony, over the middle continental shelf and the shelf break, between 43° and 51°S. The fourth individual remained in coastal areas to the south and lost the device after 15.5 days at sea. The maximum linear distance from the nest reached during a single foraging trip was 552 km. All birds were able to fly more than 400 km in 1 day, with a maximum of 513 km recorded. The maximum total distance covered in a single foraging trip was 2,540 km. Findings of this study emphasise the importance of the Patagonian continental shelf as foraging grounds for top predators in the South Atlantic Ocean.