P. A. Prince

Satellite tracking of wandering albatrosses ( Diomedea exulans ) in the South Atlantic

The movements of two wandering albatrosses, one of each sex, breeding at South Georgia, were tracked using satellite telemetry, particularly to assess whether such birds could be at risk from longline fishing operations in the subtropics. Full details of the performance (number and quality of uplinks) of the Toyocom transmitters are provided, together with data on flight speeds and night and daytime travel by the albatrosses. The female, tracked for seventeen days—covering three foraging trips totalling 13951 km - had a much more northerly distribution than the male, which made two trips to sea during the same period and travelled a minimum distance of 9280 km. On one trip the female frequented the area off Brazil known to be used for longline fisheries. The distributional differences between the sexes support earlier suggestions, based on at-sea observations, that the observed high mortality rates of South Georgian females could be due to a greater likelihood of incidental mortality in longline fishing. These results also show that the presence of females off Brazil can include birds still rearing chicks, rather than simply representing post-breeding dispersal.

Foraging white-chinned petrels Procellaria aequinoctialis at risk: from the tropics to Antarctica

In the Southern Ocean white-chinned petrels Procellaria aequinoctialis form the majority of the bird bycatch in longline fisheries. Satellite tracking of breeding birds from the Crozet islands and from South Georgia indicates that during incubation they have the longest mean foraging ranges ever recorded for a seabird, 2390 and 2190 km. Crozet birds travel to the coast of South Africa at 3495 km, into subtropical waters as well as to Antarctic waters. South Georgia birds reach the northern Patagonian shelf. In all these areas birds are potentially in contact with fisheries. These results indicate that conservation measures limited to Antarctic waters are insufficient to protect seabirds with such extensive foraging ranges.

Antarctic Seabird and Seal Monitoring Studies

The need to investigate and understand the nature of changes in abundance of economically important marine living resources has been widely recognized. They may be naturally occurring fluctuations, cycles or undirectional processes, or changes in response to artificial influences such as pollution or commercial harvesting. As direct investigation of status and population structure of some of these resources can often prove difficult, or incompatible with continuing exploitation, attention has also focussed on the identification and study of more convenient species which may be used as indices of environmental change.

Dead or alive, night or day: how do albatrosses catch squid?

For many albatross species squid are important prey. Whether albatrosses depend on scavenging (e.g. of vomit from cetaceans, post-spawning die-offs or fishery waste) or on live-capture of squid (e.g. via diel vertical migrations in association with aggregations of squid prey) is controversial. This review of the nature of interactions between squid and the four species of albatross breeding at South Georgia uses data on the foraging range, methods and timing of feeding of the albatrosses in relation to the size, distribution, buoyancy characteristics (floaters or sinkers), bioluminescence and prey of the squid and access to fishery waste. We conclude that most evidence for scavenging needs critical re-evaluation; nevertheless, whereas wandering albatrosses and possibly light-mantled sooty albatrosses probably depend significantly on scavenged squid, black-browed and especially grey-headed albatrosses are unlikely to do so.

Impact of Seabirds on Marine Resources, Especially Krill, of South Georgia Waters

Quantitative assessments of the energy and food requirements of seabird communities are few and mainly recent (Wiens and Scott, 1975; Furness, 1978; Croxall and Prince, 1982a; Ford et al., 1982; Schneider and Hunt, 1982; Sanger, 1972, 1983). Most have concerned northern hemisphere sites, particularly those of northwest Alaska. Such communities, and also that of the South African Benguela system (Furness and Cooper, 1982), are mainly dominated by species that feed inshore (usually within 50–100 km of, and often much closer to, their breeding colony), such as auks Alcidae, gulls Larus, kittiwakes Rissa and shags Phalacrocorax. This situation confers some useful advantages. First, inshore feeding birds can easily be observed and their distribution and density at sea often realistically assessed. Second, most species feed mainly diurnally and feeding ranges may be determined by direct observation from land or sea, and it may even be possible to estimate general activity budgets. Third, there is extensive information available on the biology, ecology and sometimes breeding numbers and demography of many species. Disadvantages stem principally from, first, inaccessibility because of cliff nesting habits, making handling (for collecting food samples, growth data, bioenergetic research) difficult; second, offspring of some species are precocial, departing to sea in the early stages of growth; and third, many species have broods of more than one chick, complicating studies of chick energy budgets, meal size and feeding frequency.

Weight Loss in Incubating Albatrosses and Its Implications for Their Energy and Food Requirements

-The weight loss of incubating Black-browed Albatrosses (Diomedea melanophris) and Grey-headed Albatrosses (D. chrysostoma) was measured at Bird Island, South Georgia. The rate of weight loss did not differ significantly either between the sexes or between the species. The results suggest that these two species have the same metabolic requirements. The difference in the quality of their diet leads to estimates of daily food intake considerably higher for the Grey-headed than for the Black-browed albatross. This may have been a factor in the evolution of biennial breeding in the Grey-headed Albatross. The Black-browed Albatross (Diomedea melanophris) and Grey-headed Albatross (D. chrysostoma) are widely distributed in the subantarctic zone. Their breeding biology (Tickell and Pinder 1975) and food and feeding ecology (Prince 1980) have been extensively studied at South Georgia. The timing and duration of events in their breeding cycle are similar although Greyheaded Albatrosses take approximately six weeks longer to complete the cycle. The chicks of the two species grow at different rates (Ricketts and Prince, in press), possibly as a result of difference in diet. The Black-browed Albatross feeds mainly on krill and fish whereas the Grey-headed Albatross feeds principally on squid; krill have a higher energy content (Grantham 1977) than squid (Voss 1973). The basic energy requirements of birds are closely related to their weight. Blackbrowed and Grey-headed albatrosses are similar in size and weight but the different energy content of their food suggests that they may have different energy requirements. We therefore studied the rate of weight loss in incubating birds to assess whether there is any indication of a metabolic difference between these two species.

Data on the adult marine and migratory phases in the life cycle of the southern hemisphere lamprey, Geotria australis Gray

SynopsisLarge numbers of the Southern Hemisphere lamprey, Geotria australis, have been found in the regurgitated food of albatrosses breeding on South Georgia. This finding suggests that this lamprey is found in large groups at sea, presumably associated with its host, and can travel very large distances from its natal streams. The length and morphology of the individuals from South Georgia, which almost certainly represent a South American stock, were compared with those of representatives of the immediately pre- and post-marine trophic stages of G. australis caught in Western Australia. No significant differences could be detected either in the number of trunk myomeres or in the number and arrangement of the teeth. The mean length of the animals (± 95% confidence limits) from South Georgia was 45.9 ± 0.90 cm compared with 10.0 ± 0.23 cm and 62.5 ± 0.85 cm in G. australis collected from Western Australia just before they had entered and returned from the sea respectively.

The origin of stomach oil in marine birds: Analyses of the stomach oil from six species of subantarctic procellariiform birds

Abstract The stomach oil produced by many marine birds of the order Procellariiformes is an important aspect of their breeding ecology. Fifty-seven samples of stomach oil from six species of subantarctic sea birds were examined by thin-layer and gas chromatography to determine the degree of variation in stomach oil composition between individuals of the same species. The wide variability detected, the typically marine composition of the component fatty acids and alcohols of the wax esters and triacyglycerols examined and the presence of pristane, squalene, and astaxanthin in the stomach oils all indicate that the bulk of the oil is derived directly from the food. This is in contrast to the nutritive fluids produced by secretion in several other groups of birds. Many of the stomach oils contain large amounts of wax ester and marine birds represent a significant link in the marine food web for the reconversion of zooplankton wax ester to triacylglycerol. No substantial offshore pollution by petroleum hydrocarbons was indicated by the samples; stomach oil samples from pelagic birds may be valuable in monitoring offshore pollution.

CONTRASTING STRATEGIES OF PROVISIONING AND CHICK GROWTH IN TWO SYMPATRICALLY BREEDING ALBATROSSES AT CAMPBELL ISLAND, NEW ZEALAND

Abstract The provisioning strategies of two closely related species of albatross breeding sympatrically were studied at Campbell Island, New Zealand. Black-browed Albatrosses (Diomedea melanophrys) had a higher provisioning rate of chicks than Grey-headed Albatrosses (D. chrysostoma) as a result of a higher feeding frequency. Provisioning and satellite-tracking data suggest that Black-browed Albatrosses forage over neritic waters in trips of up to 5 days, in combination with longer trips over oceanic waters. In contrast, it was not possible to separate clearly short and long trips in Grey-headed Albatrosses, but they probably forage mostly over oceanic waters, combined with rafting or feeding near the colony during stays of short duration at sea. No inter-annual differences in foraging trip duration were apparent between years for either species. Chicks were fed larger meals at older ages and when in poorer condition, probably due to a limitation on the rate of assimilation of food. For both species, chick condition after feeding did not influence the duration of foraging trips. Black-browed Albatrosses from Campbell Island feed locally in neritic waters and up to 2,000 km from the colony, in contrast to conspecifics from other sites which feed principally over neritic waters. Grey-headed Albatrosses were largely dependent on oceanic resources as for conspecifics studied elsewhere. This study shows that foraging and provisioning strategies are flexible within species, allowing them to exploit more or less distant resources.

The fish diet of black-browed albatrossDiomedea melanophris and grey-headed albatrossD. Chrysostoma at South Georgia

The fish component of the diet of black browed and grey-headed albatrosses at South Georgia was investigated by intercepting 155 meals from adults arriving to feed chicks during February 1986 and 1994. Fish represented 30% and 72% by mass of the diet of black-browed albatrosses and 14% and 60% by mass of the diet of grey-headed albatrosses in 1986 and 1994 respectively. We determined the identity and quantified the contribution (by numbers, size and mass) of fish species mainly by using otoliths (54 representing 9 taxa and 57 representing 17 taxa in black-browed and greyheaded albatross samples respectively). For blackbrowed albatrosses in 1986 the main fish prey wasPatagonotothen guntheri (77% of otoliths, 51% of estimated fish biomass) and a single large specimen ofIcichthys australis (40% estimated biomass), whereas in 1994 Pseudochaenichthys georgianus was the main fish prey (57% of estimated biomass) withMagnisudis prionosa (30%) andChampsocephalus gunnari (12%) also making substantial contributions. Grey-headed albatross samples from 1986 were dominated by southern lampreys (40% by number, 79% of estimated bio mass), lanternfish (32% of numbers, 9% by mass) andPatagonotothen guntheri (11% by mass); in 1994Champsocephalus gunnari (42% by numbers, 24% by mass),Magnisudis prionosa (13% by number, 36% by mass),Muraenolepis microps (90% by number),Pseudochaenichthys georgianus (15% by mass) and lanternfish (18% by number but only 1% by mass) were the main prey. The importance ofPatagonotothen guntheri to both species in 1986 and its absence in 1994 probably reflect albatrosses obtaining it from the commercial fishery, which was active in 1986 but closed in 1994. Otherwise the fish diet of black-browed albatrosses is dominated by krill-feeding fish, characteristic of the waters of the South Georgia shelf. In contrast, the grey-headed albatross diet comprises deeper water mesopelagic species, especially lanternfish, which reflect its affinity for the Antarctic Polar Frontal Zone and associated oceanic upwellings.