NT
Buller's Albatross Thalassarche bulleri



Justification

Justification of Red List Category
This species has been listed as Near Threatened because, although it is restricted to a small area when breeding, the population is stable and the islands on which it breeds are moderately widely spread so it is unlikely to become highly threatened in a short time owing to human activities or stochastic events.

Population justification

The estimated annual breeding population is 32,134 pairs, made up of 8,704 pairs on the Snares Islands, 5,280 pairs on the Solander Islands, 16,000 pairs on the Forty-Fours, 2,130 pairs on Big and Little Sister Islands in the Chatham Island group, and 20 pairs on Rosemary Rock, Three Kings Islands off North Island.

Trend justification

The Snares Islands population has almost doubled since 1969, but the rate of increase slowed in the 1990s and then became stable 2002-2014 (Sagar et al. 1999b, Sagar and Stahl 2005, Sagar 2014). The Solander Islands population appears to have remained relatively stable during 1985-1996, and increased by around 1.36% /annum during 1996-2016 (Sagar and Stahl 2005, Thompson et al. 2016). Overall, the population is considered stable.

Distribution and population

Thalassarche bulleri is endemic to New Zealand. There are colonies on the Snares (8,704 pairs) and Solander (5,280) islands to the south of South Island (Sagar 2014, Thompson et al. 2016), Forty-Fours (c.16,000) and Big and Little Sister (2,130) islands in the Chatham Islands group (ACAP 2009), and Rosemary Rock, Three Kings Islands (20 pairs) off North Island (Croxall and Gales 1998). This totals to approximately 32,134 breeding pairs. The Snares Islands population has almost doubled since 1969, but the rate of increase has slowed in the 1990s (Sagar et al. 1999, Sagar and Stahl 2005). The Solander Islands population appears to have remained relatively stable during 1985-1996, and has increased by around 1.36% per annum during 1996-2016 (Sagar and Stahl 2005, Thompson et al. 2016). The Chatham Island population is thought to be stable (ACAP 2009). Juveniles and non-breeding adults can disperse across the south Pacific Ocean to the west coast of South America (Stahl and Sagar 2000b, Taylor 2000, Spear et al. 2003).

Ecology

Behaviour Breeding is annual and colonial. On the Snares Islands most eggs are laid in January, hatch March to April and chicks fledge in August to September. Birds begin to return to colonies at least three years after fledging, and the average age of first breeding is 10-12 years (Francis and Sagar 2012). On the Chatham Islands, eggs are laid in October to November, hatch in January and the chicks fledge in June to July (ACAP 2009). On Little Sister, annual productivity 1994-1996 was 57-60%, and mean annual adult survival 1974-1995 was 93.5% (Croxall and Gales 1998). On the Snares, annual productivity 1995-98 was 70.8% (Sagar et al. 2002), and mean annual adult survival increased from 92.0% in 1983-85 to 95.5% in 1992-97 (Sagar et al. 2000). Breeding and non-breeding adults forage between 40 and 50°S from Tasmania eastwards to the Chatham Rise (Stahl et al. 1998, Stahl and Sagar 2000a, b, BirdLife International 2004, Sagar and Stahl 2005). Females from the Snares Islands tend to conduct longer, more distant foraging trips during pre-egg and brood guard periods of the breeding cycle, than males (BirdLife International 2004). Birds usually forage individually but large numbers may gather to feed at concentrated food sources such as swarms of crustaceans, occasionally making surface plunges or shallow dives (ACAP 2009). Satellite tracking studies from the Snares and Solander Islands show that the distribution of the breeding birds varies with the stage of the breeding cycle. During incubation (Jan-Mar) birds range along the shelf slope off the east and west coasts of the South Island, New Zealand, and into the Tasman Sea; during the guard stage (Mar-Apr) birds are usually found along the shelf slope and shelf areas east and west of the southern New Zealand; and during the post-guard stage (May-Aug) birds occur along the shelf slopes of both coasts of the South Island. After breeding, birds of all ages (including fledglings) migrate to slopes off Chile and Peru (ACAP 2009). Habitat Breeding Breeds in a variety of habitats including grassy meadows, tussock-covered slopes and cliffs, scrub and under forest canopy (Marchant and Higgins 1990). Diet It feeds mostly on fish, squid and tunicates, as well as octopuses and crustaceans (West and Imber 1986, James and Stahl 2000). 

Threats

Incidental mortality in fishing operations probably poses the greatest threat to the population and is potentially increasing. The severity of the threat appears to vary locally (ACAP 2009), but bycatch has been recorded in both pelagic and demersal fisheries in a large portion of the species’ range. It is among the most common bycatch species in the longline tuna fishery in New Zealand waters (Murray et al. 1993, Bartle 1999) and it is also caught by squid trawlers in low numbers, despite the banning of net-sonde cables in 1992 (Taylor 2000). Recent data from Chile also evinces capture in the pelagic longline swordfish fishery (ACAP 2009). In addition, the species has been recorded as bycatch in artisanal longlines off the coast of Peru (Mangel 2012), which are poorly regulated and have been subject to very little observer effort. Although the population is currently considered stable, the previous increase has now plateaued and adult survival appears to be falling (Francis and Sagar 2012) likely due to bycatch.

Climate change and associated extreme weather events (storms and flooding) also pose a threat, although seemingly of lower severity than for other albatross spp. (e.g. Northern Royal Albatross Diomedea sanfordi, Chatham Albatross Thalassarche eremita) due to nesting mainly on steep cliff margins and rough plateau basins where there is more soil (DoC 2001).

Conservation actions

Conservation Actions Underway
CMS Appendix II and ACAP Annex 1. Long-term studies have been initiated in all main populations (Taylor 2000). Most islands are legally protected, but all Chatham colonies are on private land.

Conservation Actions Proposed
Complete an accurate census on Forty-Fours and Big Sister. Census all colonies for 2-4 consecutive years every 10 years, and Little Sister at least every five years. Develop and effectively implement mitigation devices/techniques to minimise fisheries bycatch. Establish observer coverage on fisheries east of the North Island and the Chathams. Eradicate G. australis from Big Solander Island. Obtain legal protection for Forty-Fours and Sisters Islands, and continued access for research (Taylor 2000).

Identification

79 cm. Small, grey-headed, white-and-black albatross. Adult, silvery-grey forehead. Grey head, throat. Black around and in front of eye. White crescent behind and below eye. Dark grey back, upperwing, tail. White rump, underparts. White underwing with black tip, broad, sharply-demarcated band at leading edge. Large black bill, yellow on upper, lower ridges, tip. Juvenile, darker brownish-grey head, brownish bill. Similar spp. Grey-headed Albatross T. chrysostoma has broader, less distinct black leading margin to underwing. Salvin's Albatross T. salvini is larger with different underwing pattern.

Acknowledgements

Text account compilers
Stattersfield, A., Stuart, A., Fjagesund, T., Mahood, S., Martin, R., Calvert, R., McClellan, R., Moreno, R., Hermes, C., Nel, D.

Contributors
Robertson, H., Stahl, J.-C., Molloy, J., Thompson, D., McClellan, R., Waugh, S., Deppe, L., Walker, K., Sagar, P., Taylor, G.A.


Recommended citation
BirdLife International (2019) Species factsheet: Thalassarche bulleri. Downloaded from http://www.birdlife.org on 23/04/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/04/2019.