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The Bristle-thighed Curlew breeds only in North America. Its adult population numbers about 7,000 individuals, making it the rarest of the New World curlews and godwits. It is similar in appearance to the Whimbrel (N. phaeopus), having a decurved bill and robust size, but distinguished from the Whimbrel by its buffy-orange rump, voice, and unique, but often difficult to see, bristles on the thighs. The largest birds (females are typically larger than males) can have bills exceeding 100 mm and body masses over 600 g. During the boreal summer, this species breeds in two disjunct areas of western Alaska, the Nulato Hills – just east of the delta of the Yukon River – and the Seward Peninsula. The Bristle-thighed Curlew is the only species of migratory shorebird that spends the nonbreeding season exclusively in Oceania over an area stretching from the Hawaiian Archipelago south to the Pitcairn Islands and from the Marquesas Islands west to the Marshall Islands. To reach the nearest nonbreeding site in this vast area, birds from Alaska must cross at least 4,000 km of open ocean.
Bristle-thighed Curlews nest in tundra habitats on rolling hills with numerous drainages. They lay their four-egg clutch in a nest on the ground. Incubation takes about 24 days and hatch occurs in mid-to late June. Newly-hatched chicks are precocious and typically walk hundreds of meters a day. Neighboring broods often form brood groups that subsequently move together. Chicks grow rapidly and begin to fly within 21–24 days of hatching. On the breeding grounds, curlews feed on insects and spiders but also consume significant amounts of plant matter, especially crowberries and blueberries and flowers of berry-producing shrubs.
In late June and early July, curlews begin moving from breeding areas to pre-migration staging areas on the central and southern Yukon-Kuskokwim Delta and northern Alaska Peninsula. Here they congregate in low-lying tundra and meadow habitats where they rest and forage on berries that will fuel their long over-water flights. Migration begins in late July with departures peaking in August. Adult birds migrate first but are soon followed by juveniles. Curlews depart in small flocks of 10–20 individuals and birds can reach ground speeds exceeding 70 km/h.
Adult curlews are site-faithful to specific atolls and islands in Oceania during the nonbreeding season (September-April). Young birds remain in Oceania for their first three years before returning to Alaska to breed. Curlews utilize a wide range of marine and terrestrial habitats in the region and feed on invertebrates, carrion, lizards, rodents, and eggs of birds like terns. In a behavior that is unique among shorebirds, Bristle-thighed Curlews use tools (rocks) to break open eggs. Also unique to the species is their tendency to become flightless during molt. Unfortunately, this characteristic makes curlews vulnerable to predation by mammals (especially, cats, dogs, and pigs) that have been introduced into the region. There is concern that introduced mammals are eliminating or excluding curlews from areas they traditionally inhabited.
Due to their small population and threats to their nonbreeding grounds, the Bristle-thighed Curlew is a species of High Concern under the US Shorebird Conservation Plan (see http://www.fws.gov/shorebirdplan/). For more information about the Bristle-thighed Curlew see:
Marks, J. S., T. L. Tibbitts, R. E. Gill, and B. J. McCaffery. 2002. Bristle-thighed Curlew (Numenius tahitiensis). In The Birds of North America No. 705 (A. Poole and F. Gill, Eds.). The Birds of North America, Inc., Philadelphia, PA.
Marks, J. S., and R. L. Redmond. 1994. Migration of Bristle-thighed Curlews on Laysan Island: Timing, behavior and estimated flight range. Condor 96:316-330.
Gill, R. E., Jr., R. B. Lanctot, J. D. Mason, and C. M. Handel. 1991. Observations on habitat use, breeding chronology and parental care in Bristle-thighed Curlews on the Seward Peninsula, Alaska. Wader Study Group Bull. 61:28-36.
Curlews marked in Alaska and Hawaii in the past (1985–1995) still carry various colored leg bands. Birds marked in Alaska more recently (2006–2007) carry a black leg flag inscribed with a white alpha-numeric code (for example, E7). Several of these individuals are also tagged with satellite transmitters, the antennas of which are visible along their backs.
If you see a marked curlew, please note the date and location of your observation and the color, alpha-numeric code, and position of the bands on the legs of the bird. Any observations can be reported to:
Robert Gill or Lee Tibbitts
U.S. Geological Survey-Alaska Science Center,
1011 E. Tudor Rd., Anchorage, Alaska, 99503, USA,
Phone: (907) 786-3514, rgill@usgs.gov (Bob),
(907) 786 3340, ltibbitts@usgs.gov (Lee)
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