provided by EG-BAMM, Jean-Baptiste Thiebot
The wandering albatross (also referred to as 'Snowy albatross') is an iconic seabird of the Southern Ocean. This large, almost totally white, seabird is unmistakable as it glides effortlessly for hours around ships.
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Diomedea exulans breeds on remote islands of the southern oceans and roams vast expenses of the Southern Ocean. This wide ranging species has a circumpolar distribution, and both breeding and non-breeding birds have very large foraging ranges (as such, their at-sea distribution overlaps with 10 Regional Fisheries Management Organisations). Satellite tracking data indicate that breeding birds forage at very long distances from colonies (up to 4,000 km), with cases of double circumpolar navigation during the non-breeding period. Satellite tracking has also revealed that juvenile birds tend to forage further north than adults, and so do the breeding females compared to the males, in general. Foraging strategies change throughout the breeding season: during incubation stage, breeding birds forage over pelagic waters between the Antarctic continent and subtropical latitudes. During the brooding period however, adults concentrate their foraging activity in the vicinity of their breeding site, in shorter at-sea trips. During later stages of chick-rearing, D. exulans forage in short trips close to the colony in neritic waters, or in long trips far from the colony in oceanic waters to the north. Outside the breeding season, recoveries and satellite tracking data indicate initial dispersal of the birds from South Georgia across the South Atlantic Ocean to areas off South Africa, followed by migration across the Indian Ocean to winter in south-eastern Australian waters. Non-breeding and juvenile birds from the southern Indian Ocean remain north of 50°S between subantarctic and subtropical waters, with a significant proportion of them crossing the Indian Ocean to wintering grounds around the southern and eastern coasts of Australia, and eastward to the Pacific and the western coast of South America. A single adult tracked from Macquarie Island during the non breeding dispersal showed a circumpolar distribution.
Although their body is not designed for underwater locomotion, wandering albatrosses have been recorded to dive to 60 cm under the surface to seize prey (Prince et al. 1984).
The species is listed as Vulnerable in IUCN Red List, because of continuous rapid decline over three generations (70 years) at South Georgia, and strong decreases of Crozet and Kerguelen Islands populations between 1970 and 1986. Main cause of decline in this species (as with many other albatross and petrel species) is incidental mortality at sea in long-line fishing operations, because the birds may grab the baited hooks on the lines before they sink, or get entangled in the lines, generally resulting in drowning of the individuals. The consequences are reductions in not only adult survival but also juvenile recruitment. Because of its vast distribution range at sea, this species may encounter many different longline fleets indeed while foraging. The growth of the southern bluefin tuna long-line fishery in the Southern Ocean until the mid 1980s and subsequent development of the Patagonian toothfish long-line fishery coincided with the steady decline of D. exulans populations at Crozet, Kerguelen and Marion Island. Adult females are more likely to interact with the subtropical tuna fisheries as they generally distribute more northerly than males during the breeding season. The South Georgia population may be most at risk from recently developed longline fisheries operating in the south-west Atlantic throughout the year, whereas the Crozet and Prince Edward Island populations are most vulnerable to pelagic longline fishing in the Indian Ocean and Australian region. Juvenile birds forage mainly in subtropical waters where the tuna long-line fishery has expanded in recent times. Chicks are also impacted by the fisheries, as fishing hooks were found to have been ingested in half the number of chicks surveyed at Bird Island. Facing this situation, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has implemented measures which have reduced bycatch of albatrosses around South Georgia by over 99%. Recently, other Regional Fisheries Management Organisations, including the tuna commissions in the subtropical areas, have taken initial steps to reduce seabird bycatch.
On land, all breeding sites of wandering albatrosses are currently legally protected and access is restricted. However, some populations show severe reductions in breeding success owing to predation of the nestlings by alien species (such as cats on Kerguelen).
Wandering albatrosses nest in open or patchy vegetation near exposed ridges or hillocks. This habitat selection is ideal for birds with such a large wingspan that needs an open space to land and also need to jump from cliffs to take off. Yet, the downside of nesting in an open habitat is that the chicks and adults are exposed to native (giant petrels) or introduced (mice, cats) predators (e.g. Dilley et al. 2013).
The wandering albatross typically forages in oceanic areas, but may also spend substantial amount of time over shelf areas during certain stages of the breeding season. Diomedea exulans are mostly diurnal feeders, taking prey items by surface seizing. These birds are also well known for following fishing vessels, sometimes in large groups and competing for fisheries discards. Fish and cephalopods are the main components of the diet of D. exulans, with a wide variety of species caught or scavenged (~50 squid species and ~10 fish species). Patagonian toothfish is the primary fish species in the diet, potentially obtained as discarded offal.
In South Georgia, during the breeding period, fish is dominant by mass in the diet (Patagonian toothfish being the main species), with lesser proportions of cephalopods, crustaceans (mostly Antarctic krill), and jellyfish. By contrast, squids are the dominant food source of wandering albatrosses from the Indian Ocean sector (Marion and Crozet), and fish (mostly Patagonian toothfish also) accounted for a secondary proportion of the diet, with also minor occurrence of carrion. At Macquarie Island, 18 cephalopod species but no fish remains were identified in diet samples.
Their breeding season exceeds one year, and for that reason they cannot breed every year, but in the best case every second year (biennial breeding species). Note that about 30% of successful and 35% of failed breeders (on average) defer breeding beyond the expected year. Adults return to their colonies in November, about 27 days before laying their sole egg. Eggs are laid over December – January, and hatch mostly in March after an incubation period lasting 78-79 days. Chicks usually fledge in December after ~270-280 days on the nest.
After fledging, young birds usually do not return to the colonies before reaching 5-7 years old (from 3 years at South Georgia to 14 years at Crozet Islands). First age of breeding is at least 7 years old (mean age 9.6 years for females and 10.4 years for males) on Crozet Islands and at least 8 years old (mean age 10.4 years for females and 10.7 years for males) on South Georgia.
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