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BiologyBreeding in the bristle-thighed curlew probably starts around May, when the bird can be found on the Alaskan tundra (2). They are monogamous birds, forming long-term bonds, and are not only faithful to a partner, but also to breeding and wintering sites, returning to the same place year after year (5). Generally, four eggs are laid into a simple, bare depression in mossy vegetation, and both sexes will incubate the eggs for about 25 days (2) (6). The chicks leave the nest shortly after hatching, and continue to receive parental care, initially from both parents, and then just the male as the female deserts the brood before the chicks fledge (2) (6). Whilst breeding, the adults aggressively defend the eggs and chicks, and often attack potential predators or perform displays to distract them (6). After the breeding season juveniles and adults congregate on the Yukon River delta. Here they feed on berries, insects and other foods in preparation for the migration to their wintering grounds; an impressive journey in which they fly non-stop for over 4000 kilometres (2) (6). They arrive at the oceanic islands in late August to early September, where they will undergo a moult. During this moult, over 50 percent of adults become completely flightless, for a period of two weeks (2). Whilst on their wintering grounds, the curlews are opportunistic feeders, taking crustaceans, insects, spiders, snails, small fish, scorpions and the eggs of seabirds (2) (6). They show remarkable ingenuity by using rocks to crack the thick egg shells, a rare example of tool use by birds (6). Occasionally they also feed on seabird carrion and fish regurgitated by seabirds and lizards (2).