Curlews are large, long-legged wading birds that belong to the genus Numenius. They are primarily recognized as shorebirds, utilizing a wide variety of habitats, including coastal mudflats, estuaries, and inland grasslands. They play a functional role in these diverse ecosystems by acting as specialized invertebrate predators. With most species exhibiting strong migratory habits, curlews are found across nearly all major continents at various times of the year.
Distinctive Physical Characteristics
The most recognizable feature of the curlew is its long, slender, and distinctly down-curved bill, known scientifically as a decurved bill. This specialized beak can measure up to 20 centimeters in length in the Long-billed Curlew, which is the largest shorebird in North America. The bill’s unusual shape distinguishes curlews from their relatives, the godwits, which possess long bills that curve slightly upward.
Curlews are the largest birds within the shorebird group, with species like the Eurasian Curlew reaching lengths of 50 to 60 centimeters. Their long, pale legs are proportional to their size, allowing them to wade through shallow water and traverse vast mudflats. The plumage typically consists of mottled browns, buffs, and whites, providing effective camouflage against wetland and grassland habitats. Females of many species, such as the Eurasian Curlew, possess a noticeably longer bill than the male.
Global Species and Migration Patterns
The genus Numenius encompasses several living species distributed worldwide, including the Eurasian Curlew (N. arquata), the Long-billed Curlew (N. americanus), and the Whimbrel (N. phaeopus). These birds often fly thousands of kilometers between their breeding and wintering grounds. For instance, the Bristle-thighed Curlew breeds in Alaska and makes a single, non-stop flight of at least 5,000 kilometers to winter on remote Pacific islands.
The Far Eastern Curlew, the world’s largest migratory wader, travels from its breeding grounds across northeast Asia to winter in Australia and New Zealand. This extensive range and migratory lifestyle expose curlew populations to numerous threats, leading to varying conservation statuses across the globe. The Eskimo Curlew (N. borealis) was hunted until it disappeared, with no confirmed sightings since the 1960s. Similarly, the Slender-billed Curlew (N. tenuirostris) is now considered extinct.
Feeding Behavior and Vocalization
The curved bill is adapted for the curlew’s specialized foraging technique, known as probing. The bird walks slowly across soft substrates like mudflats or wet soil, inserting its bill deep into the ground to feel for hidden prey. Their diet is varied, consisting mainly of marine worms, small crustaceans, and mollusks in coastal areas. Inland or on breeding grounds, their diet shifts to include insects, such as grasshoppers and beetles, as well as berries and seeds.
The difference in bill length between the sexes may allow the female to access deeper-burrowing invertebrates, potentially reducing food competition between mated pairs. Curlews are known for their vocalizations. The English name “curlew” is an onomatopoeia, derived from the whistling “cur-lee” call often heard in their habitat. During the breeding season, males also perform a distinctive, bubbling song, often given during a circular display flight.