White-capped Albatross - Thalassarche steadi

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The Story: White-capped albatrosses are endemic to New Zealand, with the main breeding population of about 100,000 pairs at the Auckland Islands, 20 pairs on Bollons Island Antipodes Islands), and 3 pairs on the Forty Fours (Chatham Islands). Fisheries bycatch is a major threat to this albatross. It is the most common albatross species observed killed in fisheries within the New Zealand Exclusive Economic Zone (EEZ). However, the most significant fisheries-related bycatch occurs outside New Zealand waters, with an estimated 8,000 birds killed annually in trawl and longline fisheries throughout the Southern Ocean (Baker et al. 2007). Concern over this level of bycatch lead to our study of the at-sea distribution of white-capped albatrosses.

Because of difficulties accessing breeding colonies at the Auckland Islands, little was known about the species, and so almost everything we learned was new. Our main aims were to track the at-sea movements of birds throughout a year and to estimate when and where they overlapped with fisheries within the EEZ, and so we deployed a variety of tracking devices.

White-capped Albatrosses on the Auckland Islands

Most white-capped albatrosses breed only every second year. They return to their breeding colonies in October, and lay their single egg from mid-November to early December. Both parents share incubation and the off-duty bird generally forages within the EEZ. Chicks hatch from early January and during the 1st 3 weeks of its life the parents take turns to guard the chick whilst the other parent obtains food for it, again generally within the EEZ. Once the chick is large enough to cope with the weather conditions alone, both parents forage for it, both within the NZ EEZ and off eastern Tasmania. Once the chick fledges (July-August) about 80% of birds remain within Australasian waters, but the remaining 20% migrate across the Indian Ocean to feed off Namibia and South Africa.

Little is known about the diet of white-capped albatrosses, but they are assumed to feed on squid, crustaceans, fish and tunicates, which they catch at or close to the surface of the sea. However, birds often follow ships and offal is assumed to be a major part of their diet. Despite the large distances that they cover, albatrosses expend little energy when searching for food because they travel mainly using dynamic soaring. They have the ability to lock their wings open (so that they do not have to use muscles to hold them) and catch the wind to sail up before using gravity to descend with increasing speed over the ocean. Little is also known of the annual survival and longevity of white-capped albatrosses, although studies of other albatross species indicate that some birds would live for over 50 years.

Classification: Kingdom: Animalia. Phylum: Chordata. Class: Aves. Order: Procellariiformes. Family: Dimedeidae. Genus:Thalassarche. Species:steadi (Falla, 1933).

The Scientist: Paul Sagar, Scientist, NIWA.

Paul Sagar is a scientist at NIWA who started his 1st study of albatrosses in 1976. Some of the same birds that were studied in 1976 were still alive and breeding in 2014, which highlights the need for seabird researchers to be long-lived and to have students in place to carry on the research. New Zealand is the seabird capital of the world, with about 84 of the 359 species recorded worldwide breeding here. Of these seabirds, 13 of the 24 taxa of albatross breed in New Zealand, and 9 of these are endemic - breeding nowhere else in the world. With the exception of the population of Northern Royal Albatrosses breeding on Taiaroa Head, all of their breeding colonies are on offshore islands, most of which are recognised as World Heritage Sites, and so are protected from land-based threats. However, although these albatrosses breed in New Zealand they do not recognise international boundaries and range over vast areas of ocean during their lives. The area of ocean that they cover may vary from trip to trip away from the nest and from year to year, depending upon changes in the marine ecosystem that affects the prey that they seek. Unfortunately, in doing so they become exposed to a variety of threats, including bycatch and competition for the same resources from a range of fisheries.

Paul checking the band number of grey-headed albatross on Campbell island