VU
Bristle-thighed Curlew Numenius tahitiensis



Justification

Justification of Red List Category
This species is listed as Vulnerable because its population is now small and believed to be declining, probably largely as a result of predation and hunting on its wintering grounds, when perhaps more than 50% of adults are flightless during autumn moult.

Population justification
Morrison et al. (2001) estimated the population to number 7,000 breeding mature individuals and 3,000 immatures, giving a total of 10,000 individuals.

Trend justification
This species's population is suspected to be decreasing at a moderate rate, owing mainly to the expected impacts of predation and hunting on its wintering grounds.

Distribution and population

Numenius tahitiensis breeds on the lower Yukon River and central Seward Peninsula in western Alaska, USA (Collar et al. 1992). Suggestions that it breeds in Russia are unsupported (R. E. Gill in litt. 1999, 2003). It winters on oceanic islands, including the Hawaiian Islands (USA), US Minor Outlying Islands, Northern Mariana Islands (to USA), Federated States of Micronesia, Marshall Islands, Nauru, Kiribati, Tuvalu, Tokelau (to New Zealand), Fiji, Tonga, Niue (to New Zealand), Samoa, American Samoa, Cook Islands, and French Polynesia, also reaching the Solomon Islands, Norfolk Island (to Australia), Kermadec Islands (New Zealand), Pitcairn Islands (to UK) (notably Oeno) and Easter Island (Chile) (Vilina et al. 1992, Brooke 1995b, Y. Vilina in litt. 1999). The breeding population numbers c.7,000 birds, but c.3,000 subadults over-summer on Pacific islands (P. Donaldson in litt. 1999, SPREP 1999).

Ecology

It breeds in dwarf-shrub tundra at 100-350 m during May-July. Birds congregate in the Yukon-Kuskokwin Delta in August, and migrate south, mostly bypassing the Northwestern Hawaiian Islands to make landfall after 6,000 km or more (Marks and Redmond 1994b, Gill 1999). It winters on coral reefs, sandy beaches, intertidal flats, rocky shores and in palm forests and dense vegetated understorey (Gill 1999, R. E. Gill in litt. 1999, 2003). It is long-lived (15-23 years), forms long-term monogamous pairs, and is highly faithful to breeding and wintering sites (Gill 1999).

Threats

Introduced predators, especially dogs, but also cats and possibly pigs are likely to predate flightless birds on wintering grounds. The species may suffer some loss and degradation of its habitats through clearance for coconut plantations and proliferation of coconut groves where not harvested (P. Raust in litt. 2012). Hunting for food is localised, particularly previously in the Tuamotus, and recent reports suggest it may also be a threat in the Marshall Islands, Carolines, US Minor Outlying Islands and Hawaiian offshore islands (G. Allport in litt. 2006). Breeding birds are predated by several species of raptor, Parasitic Jaegers Stercorarius parasiticus, Common Ravens Corvus corax and foxes. Gold mining is a potential future threat in Alaska (R. E. Gill in litt. 1999, 2003). Ingestion of lead paint on Midway Island needs to be investigated (it was recently identified as a problem in seabirds) (R. E. Gill in litt. 1999, 2003). The species is also potentially threatened by the impacts of projected climate change through changes and geographical shifts in habitat and rising sea levels.

Conservation actions

Conservation Actions Underway
CMS Appendix II. Most breeding and staging grounds are well-protected (Gill 1999). The Hawaiian Islands National Wildlife Refuge protects several wintering and stop-over sites. Protection and management of habitat at Kahuku on O'ahu has facilitated an increase in the local wintering population (P. Donaldson in litt. 1999).

Conservation Actions Proposed
Survey key historical sites (Marks and Redmond 1994a, SPREP 1999), and identify migratory stop-over sites and sites with high concentrations of wintering birds (Marks and Redmond 1994a, SPREP 1999). Monitor population trends on its breeding grounds (Marks and Redmond 1994a, P. Donaldson in litt. 1999). Assess the harvesting rate (SPREP 1999). Protect and manage key islands, atolls and other wintering sites (Marks and Redmond 1994a, P. Donaldson in litt. 1999). Initiate a coordinated conservation programme involving stakeholders in the U.S. and Pacific nations (P. Raust in litt. 2012).

Identification

40-44 cm. Medium-sized curlew. Well-marked head pattern. Dark lateral crown and eye-stripes contrast with pale crown centre and supercilium. Upperparts spotted buff, underparts streaked buff. Dark cinnamon underwing, barred brown. Unmarked cinnamon rump and uppertail. Blue-grey legs. Flesh-coloured base to brown, longish and heavy bill. Juvenile virtually unstreaked underparts and large buff spots on wing-coverts and upperparts. Similar spp. Whimbrel N. phaeopus lacks cinnamon rump, has thinner and more pointed bill, less cinnamon underparts. Eskimo Curlew N. borealis is smaller. Long-billed Curlew N. americanus has different bill shape and head pattern. Voice Short chi-u-it, whistling whe-whe-whe-whe, ringing whee-wheeoo.

Acknowledgements

Text account compilers
Benstead, P., Harding, M., Pilgrim, J., Symes, A. & Taylor, J.

Contributors
Bird, J., Donaldson, P., Gill, R.E., Raust, P. & Vilina, Y.


Recommended citation
BirdLife International (2017) Species factsheet: Numenius tahitiensis. Downloaded from http://www.birdlife.org on 21/10/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2017.