Justification This species is classified as Near Threatened because it is thought to have a small breeding range. A higher level of threat classification might be justified if the range size is confirmed and found to be declining.

Family/Sub-family Hydrobatidae

Species name author Salvin, 1896

Taxonomic source(s) AOU checklist (1998 + supplements), Brooke (2004), Sibley and Monroe (1990, 1993)

Synonyms Hydrobates tristrami Christidis and Boles (2008)

Identification

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

20,000

unset

13,600,000 km²

Yes

Range & population Oceanodroma tristrami breeds in the Hawaiian archipelago (USA), on Nihoa (2,000-3,000 pairs), Necker, French Frigate Shoals (>20 pairs), Laysan (500-2,500 pairs), Pearl and Hermes Reef (1,000-2,000 pairs), and may also breed on Midway, Lisianski and Kure^2,3,4,5; it at least formerly bred on the Izu, Iwo and Bonin Islands, off south-east Japan¹. These estimates suggest that the world population is no greater than 30,000 birds, including 10,000 pairs⁸. This species is difficult to monitor due to its high sensitivity to human disturbance during the incubation phase⁷ and due to its habit of breeding in the winter months when access to its remote breeding colonies is more difficult. Little is known about its post-breeding dispersal, but some move north to the seas east of Japan^1,2.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: The species feeds while pattering on the sea surface, principally consuming squid and fish⁸. It nests in burrows in sand or guano, under clumps of vegetation or in recesses in scree⁸. The species is known to live for up to 14 years, at least⁷.

Threats The most serious threat to the species is the potential introduction of rats or other predators to any of its primary breeding sites⁵: a large population of O. tristrami which bred on Torishima Island until the early 1960s was apparently exterminated by introduced cats and rats^1,2, and potentially large colonies could have been extirpated from the Northwestern Hawaiian Islands for the same reason⁶. It may also be susceptible to marine pollution, with tiny plastic pellets and fragments found in one-third of the stomach samples from the Northwestern Hawaiian Islands⁵. Large-scale human activities near its colonies, including the presence of large numbers of ships, could increase mortality due to its attraction to lights⁵. Predation and irritation by introduced ants could be problem for the species¹⁰. On Laysan, the species's eggs are predated by Laysan Finches Telespiza cantans and on Nihoa, possibly by Nihoa Finches T. ultima⁷. T. cantans is known to routinely check O. tristrami burrows, but the neglect of eggs is assumed to be rare under such predation pressure. The same process is expected on Pearl and Hermes Reef where T. cantans has been introduced, possibly resulting in a reduction in nesting success⁷. However, predation by Telespiza finches is unlikely to represent a serious threat¹⁰. Extreme weather events can affect breeding; in 1913, birds on Laysan suffered heavy losses owing to the flooding of burrows, followed by sandstorms⁹.

Conservation measures underway Limited research has been carried out into the species's life history and ecology. Most of the known breeding population is protected by the Hawaiian Islands National Wildlife Refuge, which is devoid of human inhabitation, except when researchers are present⁷. A recent research project has investigated the potential threat from introduced ants¹⁰.

Conservation measures proposed Expand research efforts into its ecology. Monitor population trends. Improve knowledge of its status on Japanese islands. Quantify the effect of Telespiza cantans and T. ultima on breeding success⁷. Take every effort to prevent the introduction of predators to breeding sites.

References 1. Carboneras (1992a). 2. Enticott and Tipling (1997). 3. Rauzon et al. (1985). 4. Baker et al. (1997). 5. Harrison (1990). 6. C. S. Harrison in litt. (1999). 7. Marks and Leasure (1992). 8. Brooke (2004). 9. Warham (1990). 10. E. VanderWerf in litt. (2007).

Further web sources of information

Fully detailed species accounts from the Threatened birds of Asia: the BirdLife International Red Data Book (BirdLife International 2001), together with new information collated since the publication of the Red Data Book

Text account compilers David Capper (BirdLife International), Andrew O'Brien (BirdLife International), Joe Taylor (BirdLife International)

Contributors C.S. Harrison, Eric VanderWerf (Pacific Rim Conservation)

IUCN Red List evaluators Stuart Butchart (BirdLife International), Joe Taylor (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Oceanodroma tristrami. Downloaded from http://www.birdlife.org on 9/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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