Bristle-thighed Curlew Life History

Habitat

Bristle-thighed Curlews breed in arctic areas with rolling hills covered with upland tundra. The higher parts of these areas have very short or no vegetation, while the lower sections host shrubby vegetation. After breeding, birds move to staging areas on the Yukon Delta, where they feed on fruits in sedge-grass meadows and tundra to prepare for their long-distance, nonstop migration flight. On their nonbreeding grounds in the Pacific, Bristle-thighed Curlews use tidal mudflats, marshy areas, edges of mangrove swamps and lagoons, reefs, saltpans, channels between islets, and beaches. On some islands, curlews forage mainly in inland open areas including lawns and airport runways.

Food

In Alaska, Bristle-thighed Curlews feed extensively on fruits—especially black crowberries, lingonberries, bog cranberries, bog blueberries, and cloudberries—as well as insects, spiders, and the flowers of dwarf shrubs. On the nonbreeding grounds, this species eats almost anything, including marine and terrestrial invertebrates, seabird eggs and chicks, carrion, lizards, rodents, and fruits.

With such a varied diet, Bristle-thighed Curlews employ a variety of foraging techniques: running after invertebrates on snowfields; probing for invertebrates on tundra, beaches, mudflats, and coral reefs; and plucking fruits and flowers from low shrubs. On their nonbreeding grounds, they also use a technique known as “slamming,” in which they hold a crab or snail in their bill and then throw it against a rock to break open the hard shell. In a twist on this “slamming” technique, some Bristle-thighed Curlews also use tools to obtain food, throwing small pieces of coral against abandoned seabird eggs to create holes in the eggs.

Nesting

Nest Placement

Placed on the ground in low tundra vegetation, usually in dwarf-shrub meadows. Nests placed under dwarf willows are more likely to hatch than nests not protected by willows.

Nest Description

A simple bowl in tussock or moss, lined with old leaves, lichens, and pieces of mosses, sedges, and twigs.

Nesting Facts

Behavior

Bristle-thighed Curlews are powerful fliers, befitting a species that migrates nonstop at least 4,000 km (2,500 miles) between breeding and nonbreeding grounds. During the nesting season, males perform elaborate flight displays, flying upward on quick, shallow wingbeats to heights of 5–20 meters (16–66 feet), then gliding on fixed wings, often singing. On the nonbreeding grounds, Bristle-thighed Curlews are unique among shorebirds in becoming temporarily flightless while they replace most of their flight feathers all at once.

This species is socially monogamous, but early in the breeding season males attempt to mate with additional females. Both sexes build the nest and incubate the eggs. Chicks hatch covered in down with their eyes open and leave the nest within 12 hours of the last egg hatching. Both parents are very active in caring for their young for 3–4 weeks. Many parents leave their chicks after this time, leaving the young birds to flock together under the care of a small number of adults. This process, known as brood amalgamation, is a rare phenomenon among shorebirds.

Conservation

Partners in Flight estimates Bristle-thighed Curlew’s global population size at 10,000 breeding individuals and rates the species a 17 out of 20 on the Continental Concern Score, indicating a Red Watch List species of high conservation concern. In addition, the 2022 State of the Birds report for North America identified Bristle-thighed Curlew as a “Tipping Point” species, because it lost 50% of its population between 1970 and 2019, has a “perilously small” population, and continues to face high threats.

Bristle-thighed Curlew censuses in 2021 and 2022 in French Polynesia, an important nonbreeding area, indicate that the species has declined by about 50% over the last two decades. This species is flightless while it molts its wing feathers on the nonbreeding grounds, making it susceptible to predation by introduced mammals like dogs and rats. Sea-level rise caused by climate change is likely to pose another threat to this species, shrinking the amount of suitable habitat on island nonbreeding grounds.

Credits

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Jiguet F. Population trends, size, and potential threats to Bristle-thighed Curlew Numenius tahitiensis: new data from French Polynesia. Bird Conservation International. 2023;33:e62. doi:10.1017/S0959270923000151

Marks, J. S. and C. S. Hall. (1992). Tool use by Bristle-thighed Curlews feeding on albatross eggs. Condor 94:1032-1034.

Marks, J. S., T. L. Tibbitts, R. E. Gill, and B. J. McCaffery (2020). Bristle-thighed Curlew (Numenius tahitiensis), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.

McCaffery, B.J. and Gill, R.E. (1992). Antipredator strategies in breeding Bristle-thighed Curlews. American Birds. 46(3): 378–383.

Partners in Flight (2023). Avian Conservation Assessment Database, version 2023.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Back to top