NT
Bristle-thighed Curlew Numenius tahitiensis



Justification

Justification of Red List Category
This species is listed as Near Threatened because its moderately small population is feared to be declining slowly, probably largely as a result of predation and hunting on its wintering grounds. The intensity of hunting has decreased considerably in recent years, and there are signs that the species is recovering in parts of its range.

Population justification
The population is estimated to number 10,000 mature individuals (Andres 2012 per Partners in Flight 2019). Despite breeding in two different areas in Alaska, the species does not show spatial segregation in the non-breeding grounds (Sonsthagen et al. 2015) and can therefore be considered one subpopulation.

Trend justification
The population trend is difficult to quantify. On the breeding grounds in the Arctic, trends are inconclusive. There is concern that the species may be undergoing a decline: Wetlands International (2020) list the species as declining between 2002 and 2011. Partners in Flight (2019) and Smith et al. (2020) describe the trend as unknown or possibly declining, while a population survey found no evidence of declines (G. Butcher in litt. 2007). On the non-breeding grounds in Oceania, the species is thought to be stable in French Polynesia (P. Raust in litt. 2020) or even increasing on Oahi (Hawaii) due to recolonisation events (Tibbitts et al. 2020). Overall, there seems to be growing evidence that population declines have stopped or at least slowed down considerably. In the absence of data covering the entire range, it is precautionarily suspected that the species has been undergoing a slow decline over the past three generations (23.1 years), which is unlikely to exceed a rate of 5-10%.

Distribution and population

Numenius tahitiensis breeds on the lower Yukon River and central Seward Peninsula in western Alaska, U.S.A. (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), U.S. Minor Outlying Islands, Northern Mariana Islands (to U.S.A.), 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 1995, Y. Vilina in litt. 1999).

Ecology

The species breeds in dwarf-shrub tundra at 100-350 m during May-July. Individuals 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). The species 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

On the non-breeding grounds in Polynesia, introduced predators, especially dogs, but in the past also cats and possibly pigs, are predating flightless birds (P. Raust in litt. 2020). 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 occurring localised, particularly 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). In recent years, hunting for food has however considerably declined in Polynesia or even stopped entirely (P. Raust in litt. 2019, E. VanderWerf in litt. 2020). 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, see also Pearce-Higgins et al. 2017, Marks et al. 2020). The species is also potentially threatened by the impacts of projected climate change through changes and geographical shifts in habitat and rising sea levels (Pearce-Higgins et al. 2017). Breeding birds are predated by several species of raptor, Arctic 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).

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 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). 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
Hermes, C.

Contributors
Allport, G., Andres, B.A., Benstead, P., Butcher, G., Donaldson, P., Gill, R.E., Harding, M., Pilgrim, J., Raust, P., Symes, A., Taylor, J., Tibbitts, L., VanderWerf, E. & Vilina, Y.A.


Recommended citation
BirdLife International (2022) Species factsheet: Numenius tahitiensis. Downloaded from http://www.birdlife.org on 27/06/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/06/2022.