Justification of Red List Category
This species is listed as Endangered as it has a very small breeding range and is estimated to be undergoing a very rapid decline projected over three generations (72 years) owing to incidental mortality in longline fisheries.
On Gough Island, the population was estimated at c.5,300 breeding pairs in 2000-2001 (Cuthbert and Sommer 2004). In 2015, the number of breeding pairs in the Tristan da Cunha group was estimated to be 15,250 on Tristan da Cunha Island, 4000 on Nightingale Island in 2007, 40 on Middle Island in 2010, 210 on Stoltenhoff Island in 2009 (Fraser et al. 1988, Ryan and Ronconi 2011, RSPB unpubl. data) equating to 52,000 mature individuals (range: 35,000-73,500).
On Inaccessible Island, a partial count in 1999-2000 suggests that the population may have decreased since the late 1980s (Ryan and Moloney 2000). On Nightingale, the population has declined from 3,000 pairs in 1972-1974 to 1,000 pairs in 1999 (P. G. Ryan in litt. 2000), and counts at 4 sites indicate an annual decrease of 3-4% between 2005-2015 (RSPB, Tristan Government unpublished data). Counts of the Gough Island study colony indicate that numbers within this small area underwent a period of decline (from 1982 to 1994) followed by an increase (1994 to 2008), with numbers now at similar levels to the early 1980s. Population counts from 11 representative areas of Gough Island (c. 5% of breeding habitat) indicate a decline of 2-3% per year, similar to population modelling with 20 years of demographic data (1982-2001) predicts annual rates of decrease of between 1.5-2.8% on Gough Island and 5.5% on Tristan da Cunha (Cuthbert et al. 2003; though one small study area is stable, perhaps because of immigration), and overall declines are estimated to exceed 70% over 72 years (three generations), placed here in the band 50-79% because of the level of uncertainty involved.
Thalassarche chlororhynchos breeds on Gough and islands in the Tristan da Cunha archipelago, Tristan da Cunha, St Helena (to U.K.). On Gough, the population was estimated at c.5,300 breeding pairs in 2000-2001 (Cuthbert and Sommer 2004a). In the Tristan da Cunha Island group, the number of breeding pairs per year was estimated to be 15,250 (10-90% CI: 9300-23,900; RSPB unpubl. data) on Tristan da Cunha Island in 2015, 4,000 on Nightingale Island in 2007 (ACAP 2009), 40 on Middle Island in 2009 (Ryan et al. 2011), 210 on Stoltenhoff Island in 2009 (Ryan et al. 2011), and 1,100 on Inaccessible Island in 1983 (Fraser et al. 1988). These data give a total of about 26,000 breeding pairs per year, equating to 52,000 (range: 35,000-73,500) mature individuals. Demographic data have been collected from three study colonies on Gough Island, Nightingale Island, and Tristan da Cunha. Annual variation in the number of breeding birds was strongly correlated between the Gough and Tristan islands and over the whole study period both study populations have decreased at around 1.1-1.2% per year (Cuthbert et al. 2003). However, population modelling predicts annual rates of decrease of between 1.5-2.8% on Gough Island and 5.5% on Tristan da Cunha, though counts at a small monitoring site indicate a stable population from 1984-2015 (Cuthbert et al. 2003, 2014, RSPB and Tristan Government unpubl. data). On Inaccessible Island, a partial count in 1999-2000 suggests that the population may have decreased since the late 1980s (Ryan and Moloney 2000). In the non-breeding season it disperses throughout the South Atlantic Ocean, mainly between 25°S to 50°S, and has been recorded off the coast of Argentina, Brazil and the west coast of southern Africa (Harrison 1983). A single bird collected at Middle Sister Island (Chatham Islands) in the 1970s had recently laid an egg.
Behaviour This species is an annual breeder. Nests are a pedestal made of mud, peat, feathers and vegetation. Eggs are laid September to early October, and chicks fledge in late March to April. Young birds return to colonies from five years of age, and experienced breeders will attempt to breed in two of every three years. Breeding success ranges from 62-72% and 62-76% for Gough Island and Tristan de Cunha respectively (ACAP 2009). It usually breeds singly or in loose aggregations. It feeds by surface-seizing and occasionally diving, and also feeds in association with marine mammals or gamefish which bring baitfish to the surface. It is strongly attracted to fishing vessels and studies from shelf waters have shown scavenged food can comprise a large proportion of stomach contents. Habitat Breeding It builds nests built on tussock grass, on rocks and under trees. Diet When not scavenging, its diet is largely comprised of fish, but also cephalopods (ACAP 2009). In one study, cephalopods were predominant in the diet of birds caught by longlines, representing 73% of the total mass (Colabuono and Vooren 2007).
The main threat facing this species is incidental capture in commercial longline fisheries. There is an estimated bycatch mortality of at least 900 birds per annum off the coast of south-east Brazil, where it is known to be one of the most common species attending longline vessels (Olmos et al. 2000). It is also known to attend trawlers and longlining vessels off the west coast of southern Africa (Harrison 1985, Olmos 1997, Croxall and Gales 1998), where mortality has been recorded, but not quantified (Ryan et al. 2002). It is one of the most frequently killed species in longline fisheries off Namibia (Paterson et al. 2017). In addition, the species may still suffer some direct persecution; the harvest of chicks and adults on Tristan da Cunha was previously permitted under a local ordinance, but is now illegal and the practice appears to have discontinued, although some poaching of eggs and chicks may still occur (Rothwell 2005).Introduced House Mice Mus musculus are present on both Tristan da Cunha and Gough Island, and known to depredate seabird nests. Cuthbert et al. (2013) estimated that mice caused a minimum of 2% chick mortality on Gough Island. Despite low mean levels of predation, there was considerable local variation in chick mortality; at one site only 7% of chicks survived to fledge. Inspection of nests post-breeding revealed that c. 10% of nest cups had mouse burrow entrances directly into the cup (Cuthbert et al. 2013), suggesting that this mortality could be causing slow, significant declines. Historically, Wild Boar Sus scrofa negatively impacted adults, chicks and eggs on Inaccessible Island, but are now absent from the island.
Conservation Actions Underway
CMS Appendix II and ACAP Annex 1. It is monitored on Gough, Nightingale, and Tristan da Cunha. Gough and Inaccessible Islands are nature reserves and a World Heritage Site. A population census on Gough was conducted in 2000-2001, and a repeatable monitoring protocol was devised (Cuthbert and Sommer 2004). Remote-tracking of several populations has been undertaken. Limited counts were made in a few areas on Tristan da Cunha during 2004 and limited monitoring is ongoing. In 2006 the South East Atlantic Fisheries Commission (SEAFO) passed a resolution to require all its longline vessels to use a tori line and to set lines at night.
81 cm. Small albatross. Blackish grey saddle, tail and upperwing. Underparts mostly white, underwing showing narrow black margin and primaries. Head pale grey with white nape and hindneck (nominate) or all white in sub-species bassi. Black bill with yellow upper surface (culmenicorn) and pinkish tip. Juveniles similar to adults but head entirely white and bill all black. Similar spp. Can be differentiated from T. carteri by grey wash on cheeks, and larger black eye patch. Adults similar to, but significantly smaller than, adult Grey-headed Albatross Thalassarche chrysostoma and the latter show a darker grey head, different bill pattern and have wider black margins in the underwing.
Text account compilers
Stuart, A., Sullivan, B., Symes, A., Calvert, R., Fjagesund, T., Butchart, S., Anderson, O., Hermes, C., Martin, R., Moreno, R., Small, C.
Ryan, P.G., Bond, A., Hilton, G., Cooper, J., Cuthbert, R.
BirdLife International (2020) Species factsheet: Thalassarche chlororhynchos. Downloaded from http://www.birdlife.org on 25/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/10/2020.