Diomedea dabbenena 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Procellariiformes Diomedeidae

Scientific Name: Diomedea dabbenena
Species Authority: Mathews, 1929
Common Name(s):
English Tristan Albatross
Diomedea chionoptera subspecies chionoptera Mathews, 1929 [in Robertson and Nunn (1998)]
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.
Taxonomic Notes: Diomedea exulans (Sibley and Monroe 1990, 1993) has been split into D. exulans, D. dabbenena and D. antipodensis following Brooke (2004), contra Robertson and Nunn (1998) who also split antipodensis into T. antipodensis and T. gibsoni.

Identification information: 110 cm. Huge albatross, very similar in plumage to Wandering Albatross D.exulans. Probably indistinguishable in field, but plumage generally darker. Separated by smaller size (e.g. bill c. 25 mm shorter) (Neves et al. 2000) and slower acquisition of white adult plumage, never attaining very white plumage of old male D. exulans.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A4ade ver 3.1
Year Published: 2015
Date Assessed: 2015-10-01
Assessor(s): BirdLife International
Reviewer(s): Symes, A.
Contributor(s): Cooper, J., Croxall, J., Cuthbert, R., Hilton, G., Ryan, P.G. & Wanless, R.
Facilitator/Compiler(s): Anderson, O., Calvert, R., Mahood, S., McClellan, R., Nel, D., Shutes, S., Stattersfield, A., Sullivan, B., Symes, A., Taylor, J., Martin, R & Ashpole, J
This species qualifies as Critically Endangered owing to its extremely small breeding range and a projected extremely rapid population decline over three generations (70 years). Modelled population declines are a consequence of very low adult survival owing to incidental mortality in longline fisheries, compounded by low fledging success caused by predation of chicks by introduced mice.

Previously published Red List assessments:
2013 Critically Endangered (CR)
2012 Critically Endangered (CR)
2010 Critically Endangered (CR)
2009 Critically Endangered (CR)
2008 Critically Endangered (CR)
2007 Endangered (EN)
2005 Endangered (EN)
2004 Endangered (EN)
2003 Endangered (EN)
2000 Endangered (EN)
1994 Not Recognized (NR)
1988 Not Recognized (NR)

Geographic Range [top]

Range Description: Diomedea dabbenena breeding populations are essentially restricted to Gough Island, Tristan da Cunha, St Helena (to UK), having become extinct on Tristan (although birds were seen prospecting in 1999 [Ryan et al. 2001]), and in some years one pair breeds on Inaccessible Island (Cuthbert et al. 2003, R. Wanless in litt. 2007). Using consecutive annual accounts of incubating adults and a population model the population has been estimated at c. 1,700 breeding pairs, giving a total global population of 7,100 individuals (ACAP 2010). Recent counts suggest that the population on Gough has decreased by 28% over 46 years, and at 3% annually between 2000 and 2011 (Cuthbert et al. 2014), in line with population modelling predictions of annual decline rates of 2.9-5.3% (Ryan et al. 2001, Wanless et al. 2009), equivalent to declines of >96% in three generations. Predation of chicks by mice has led to very low breeding success; between 2000 and 2011 this averaged only 23%, less than half that of other studied Diomedea colonies (Cuthbert et al. 2003, Cuthbert and Hilton 2004, Wanless et al. 2007, R. Wanless in litt. 2007, Cuthbert et al. 2014).  Breeding success in 2014 was just 9.6%, the lowest recorded since counts started in 2001 (Davies et al. 2015). In January 2008, 1,764 adult albatrosses were incubating eggs on Gough but only 246 chicks survived to fledging (BirdLife International 2009). Outside the breeding season, it disperses to South Atlantic and South African waters (Goren and Ryan 2010), with numerous recent records from Brazilian waters (Neves et al. 2000, Olmos et al. 2000) and one from Australia (Ryan et al. 2001), suggesting that birds may occasionally disperse into the Indian Ocean. This is supported by the recent record of a ringed individual washed up on the Indian Ocean coast of South Africa (Ryan 2009).

Countries occurrence:
Angola (Angola); Argentina; Brazil; Namibia; Saint Helena, Ascension and Tristan da Cunha (Tristan da Cunha); South Africa; Uruguay
Estimated area of occupancy (AOO) - km2: 80
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2:
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 1
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Lower elevation limit (metres): 400
Upper elevation limit (metres): 700
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Breeding populations are essentially restricted to Gough Island, with a single pair nesting intermittently on Inaccessible Island (ACAP 2009). The annual breeding population is currently estimated to be 1,698 pairs (2010), equivalent to a total population of 7,100 individuals for this biennially breeding species (RSPB unpublished data). This roughly equates to 4,700 mature individuals.

Trend Justification:  Recent counts suggest that the population on Gough has decreased by 28% over 46 years, and at 3% annually between 2000 and 2011 (Cuthbert et al. 2014), which is in line with population modelling predicting annual rates of decline of 2.9-5.3% (Ryan et al. 2001, Wanless et al. 2009). More recent population modelling, conducted over three generations since 1980, suggests a decline equivalent to a >96% reduction in population size over three generations, since declines began (BirdLife International unpublished data). The rate of ongoing decline is therefore placed here in the band 80-100% over three generations (86 years).

Current Population Trend: Decreasing
Additional data:
Number of mature individuals: 4700 Continuing decline of mature individuals: Yes
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 1 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: Yes
No. of individuals in largest subpopulation: 100

Habitat and Ecology [top]

Habitat and Ecology: Behaviour It is a colonial, biennially breeding species. Adults return in November and December, lay in January and the chicks fledge in November. Immature birds begin returning to their breeding colony at 3-7 years after fledging. Most D. dabbenena recruit in their natal colony, at a mean age of 10 years (range 4-20 years) (ACAP 2009). The oldest recorded bird was at least 38 years old (Ryan 2009). It catches prey by surface-seizing, and the prevalence of a bioluminescent group of cephalopods in one dietary study suggests that D. dabbenena often feed at night (ACAP 2009). During the breeding season the length and range of foraging trips varies considerably, depending on the stage of the breeding cycle (BirdLife International 2004, Cuthbert et al. 2005). Habitat Breeding It nests at 400-700 m (rarely to 300 m) (P. G. Ryan in litt. 1999), primarily in wet heath where it is open enough for take-off and landings. Diet It feeds on cephalopods and fish (J. Cooper in litt. 1999), and probably follows ships and trawlers for offal and galley refuse.

Systems: Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 28.7
Movement patterns: Full Migrant
Congregatory: Congregatory (and dispersive)

Threats [top]

Major Threat(s): On Inaccessible Island, its decline was probably due to predation by feral pigs (now absent) and humans (Fraser et al. 1988, Ryan et al. 1990). The failure to recover is unclear, but may be because young birds become entangled in thick vegetation (Ryan et al. 1990, P. G. Ryan in litt. 1999). On Tristan, its extirpation was probably the result of human exploitation (J. Cooper in litt. 1999), although predation by rats may have been a factor (Fraser et al. 1988). On Gough, predation by the introduced house mouse Mus musculus causes very low breeding success and alone is sufficient to drive a population decline of over 50% over three generations (Cuthbert et al. 2003, Cuthbert and Hilton 2004, Wanless et al. 2007). In 2014, 20 chicks were closely monitored in the Gonydale study area on Gough. Of these 20 chicks, 15 failed to fledge. Fourteeen of the fifteen failures (93%) were caused by mouse predation (Davies et al. 2015). Mouse attacks on chicks peaked in May-June at the start of the austral winter. All predation took place at night, usually 1-2 mice were recorded attacking the chick, with death occurring 3.9 ±1.2 days after the first attack (Davies et al. 2015). An additional threat on Gough is peat slips caused by storms burying and killing nestlings and adults, although this is probably a very rare event (Ryan 1993).

Another major threat comes from interactions with longline fisheries, with a high proportion of "Wandering" Albatross bycatch in southern Brazilian waters being of this species (Neves et al. 2000, Olmos et al. 2000), including a few birds banded at Gough (Croxall and Gales 1998, J. Cooper in litt. 1999). It has been estimated that c. 500 individuals of this species are killed every year by longliners (Goren and Ryan 2010). Satellite tracking of breeding birds indicates considerable overlap between birds and areas of longline fishing (Cuthbert et al. 2005), although due to lag times associated with albatross demography we are probably only now likely to start to pick up population trends associated with longline mortality (R. Wanless in litt. 2007). A study of great albatross bycatch from Uruguayan and Japanese longline fisheries in the south-west Atlantic off Uruguay found most Tristan albatross bycatch occurred between September and November in pelagic waters where many other fleets operate (Jiménez et al. 2014). Together, the dual threats of mice and bycatch give a worst-case scenario of extinction in roughly 30 years, although the true situation is likely a continued and severe decline (Wanless et al. 2009). Having a distribution on relatively low-lying islands, this species is also potentially susceptible to climate change through sea-level rise and shifts in suitable climatic conditions (BirdLife International unpublished data).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
ACAP Annex 1. On Tristan, a programme to eradicate cats was successful in the 1970s. Gough and Inaccessible are nature reserves and Gough is a World Heritage Site. Both islands are uninhabited, apart from a meteorological station on Gough (Cooper and Ryan 1994). Satellite tracking to determine foraging areas during the breeding season was undertaken in 2000-2001 (Cuthbert et al. 2003). Censuses of large chicks and/or incubating adults were carried out during 1999-2003, and a monitoring protocol was devised (Cuthbert and Sommer 2004). Satellite tracking of non-breeders, further monitoring and demographic work, and an investigation of mouse predation on chicks was initiated during 2003-2006. Initial results from a feasibility study into the removal of the mice appear promising, giving no significant obstacles to the undertaking of an eradication programme (BirdLife International 2009). In September 2013 a trial drop of non-toxic bait over the vegetated cliffs of Gough showed that around 80% of the bait was retained on the cliffs and would be accessible to mice living there (Ryan 2013). Since 2007, birds have been marked with field-readable plastic leg rings, and by 2009, 650 individuals had been ringed (Goren and Ryan 2010).

Conservation Actions Proposed
Annually survey numbers and assess breeding success on Gough. Continue research of at-sea distribution and foraging behaviour, particularly of non-breeding birds. Promote adoption of best-practice mitigation measures in all fisheries within the species's range, particularly via intergovernmental mechanisms such as ACAP, FAO and Regional Fisheries Management Organisations. Use decoys to assist re-establishment of birds on Tristan, and to attract birds to Long Ridge on Inaccessible (P. G. Ryan in litt. 1999). Begin an eradication programme for mice on Gough Island as soon as possible.

Citation: BirdLife International. 2015. Diomedea dabbenena. The IUCN Red List of Threatened Species 2015: e.T22728364A79003664. . Downloaded on 02 December 2015.
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