Pterodroma atrata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Procellariiformes Procellariidae

Scientific Name: Pterodroma atrata Mathews, 1912
Common Name(s):
English Henderson Petrel
Spanish Fardela de Henderson
Taxonomic Source(s): Brooke, M. de L. 2004. Albatrosses and Petrels Across the World. Oxford University Press, Oxford.
Identification information: 36 cm. Medium-sized, slight, dark grey-brown, gadfly petrel. Fairly uniform grey-brown plumage, somewhat paler on underparts. Greyer feather tips on forehead and chin give mottled appearance around bill. Underwing shows pale leading edge between carpal joint and body, and some silvery-white at base of primaries. Black bill. Pink legs, with pink feet proximally, black distally. Similar spp. Dark phase Kermadec Petrel P. neglecta slightly bigger, with white primary shafts, and wholly black legs. Murphy's Petrel P. ultima is a greyer bird. Providence Petrel P. solandri is distinctly larger, and usually has more facial frosting.

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(v) ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Brooke, M., Hall, J., Wragg, G., Bond, A. & Oppel, S.
Facilitator/Compiler(s): Anderson, O., Calvert, R., Mahood, S., Moreno, R., O'Brien, A., Pople, R., Shutes, S., Stattersfield, A., Symes, A.
This species qualifies as Endangered as it probably breeds at fewer than five locations (although currently only known from one) and its population is suspected to be declining as a consequence of predation by rats.

Previously published Red List assessments:

Geographic Range [top]

Range Description:

Pterodroma atrata is known to breed only on Henderson Island, Pitcairn Islands (to UK), but may have also bred on Pitcairn Island in the past and has apparently become extirpated from Ducie, also in the Pitcairn Islands (Brooke 1995a). It is possible it also breeds on the Gambier and Marquesas Islands (French Polynesia) (Murphy and Pennoyer 1952, Thibault and Bretagnolle 1999), but there has been no conclusive evidence. While its non-breeding range is not well known, it has been sighted at Easter Island (A. Jaramillo in litt. 2011). Birds may range up to 2500 km from Henderson Island during incubation (Oppel et al. in press). 

Countries occurrence:
Present - origin uncertain:
French Polynesia; Kiribati
Additional data:
Estimated area of occupancy (AOO) - km2:43Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:9820000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1-5Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):33
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In 1991-1992, the breeding population on Henderson was estimated at c.16,000 breeding pairs, though using the incorrect island area. The revised estimate is 18,668 pairs (Oppel et al. in press), and it was suggested that the species could be undergoing a long-term decline (Brooke 1995a, Brooke et al. 2010). In 2015, the population was estimated to be 19,987 pairs (Oppel et al. in press).The population trend is unknown, but based on very sparse data. High variability in breeding success suggests the population may be declining, but infrequent surveys (1991, 2015), which do not suggest any substantial change, make this difficult to confirm.

Trend Justification:  The species is declining slightly as a result of predation by introduced mammals.

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

Habitat and Ecology [top]

Habitat and Ecology:Like P. heraldica it may feed predominantly on cephalopods, also taking fish and crustaceans (Imber et al. 1995). On Henderson, it nests exclusively on the plateau, scattered in the dense forest, though nearer to the coast than P. heraldica (Brooke 1995a, Brooke and Rowe 1996, Oppel et al. in press). Breeding success may be low, with less than 20% of eggs yielding fledglings and failure mostly occurring at the early chick stage (Brooke 1995a), but was 28-50% in 2015 (Oppel et al., in press), which is sufficient for a stable population using the demographic parameters from Brooke et al. (2010). In other absence of other known colonies elsewhere, there is no source of immigrants to sustain the Henderson petrel population (Brooke 2010). 

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):15.6
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): Predation by Polynesian rat Rattus exulans is believed to be the main cause of chick mortality on Henderson, although predation by crabs Coenobita spp. is also a possibility (Brooke 1995a, Oppel et al. in press). In August 2011, a rat eradication operation was carried out on Henderson Island to eradicate R. exulans from the island (J. Hall in litt. 2012), but the project failed, with little apparent impact on the Henderson Petrel population (Oppel et al. 2016). If the species ever bred on Pitcairn, it is likely to have been extirpated there because of predation by feral cats and introduced rats (Brooke 1995a), which affect other surface-nesting petrels (Schofield and Bond, in press). 

Conservation Actions [top]

Conservation Actions:

Conservation Actions Underway

In 1997, feral cats were eradicated from Pitcairn, but subsequently re-introduced by residents. A programme to eradicate rats in 1997-1998 (Bell and Bell 1998) was unsuccessful, although petrels were observed prospecting the island during a period of no cats and low rat numbers (G. Wragg in litt. 1999). In the same year, rats were eradicated on Oeno and Ducie to increase the chance of another P .atrata population becoming established there (Bell and Bell 1998). Several follow-up visits to Oeno and Ducie have not found any signs of rats (M. de L. Brooke in litt. 2000, 2003). Following a feasibility study (Brooke and Towns 2008) a rat eradication operation was carried out on Henderson Island in August 2011, but was unsuccessful (Amos et al. 2016). In 1988, Henderson was designated a World Heritage Site. A rudimentary monitoring protocol was established on Henderson in 2003 (M. de L. Brooke in litt. 2000, 2003).

Conservation Actions Proposed

Eradicate rats from Henderson Island. Periodically resurvey the species to establish and monitor any trends. Periodically check Oeno and Ducie for rats and nesting P. atrata, and ensure that further alien species are not accidentally introduced to the Pitcairn Islands.

Citation: BirdLife International. 2016. Pterodroma atrata. The IUCN Red List of Threatened Species 2016: e.T22728442A94985978. . Downloaded on 26 September 2018.
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