Slender-billed Curlew

The Slender-billed Curlew, Numenius tenuirostris, is a small member of the wader family Scolopacidae. With a length of 36–41 cm and a wingspan of 77–88 cm, it is comparable in size to the Eurasian Whimbrel. The species exhibits a greyish brown plumage above with a whitish rump and lower back during the breeding season. Its underparts are white, heavily streaked with dark brown, and the flanks are adorned with round or heart-shaped spots. In non-breeding plumage, the bird retains a similar appearance but with fewer spots on the flanks. Both sexes share the same plumage, though females possess longer bills than males, reducing competition for food.

Identification Tips

Distinguishing the Slender-billed Curlew from similar species relies on several key features. It is whiter on the breast, tail, and underwing compared to the Eurasian Curlew, and its bill is shorter, more slender, and slightly straighter at the base. The head pattern includes a dark cap and a whitish supercilium, reminiscent of the Whimbrel, though the Slender-billed Curlew lacks the central crown stripe and has a less distinct overall pattern. The most reliable identification markers are the uniformly dark underside of the outer primaries, darker legs (black in adults), and a white tail with fewer dark bars.

Habitat

The Slender-billed Curlew historically bred in the forest bogs of Siberia, though its exact nesting grounds have remained a mystery since the last documented nest in 1924.

Distribution

This curlew was known to breed in a limited area north of Omsk, Russia, and primarily migrated to the Mediterranean and southern Arabia for wintering. It has been recorded as a vagrant in various locations including western Europe, the Canary Islands, the Azores, Oman, Canada, and Japan.

Behaviour

The Slender-billed Curlew's breeding biology is largely unknown, but observed nests typically contained four eggs. It feeds by probing soft mud for invertebrates and occasionally picking items from the surface. Historically, it was highly sociable outside the breeding season, often associating with related species like the Eurasian Curlew.

Song & Calls

The species emits a "cour-lee" call, akin to the Eurasian Curlew but higher-pitched, more melodic, and shorter. Its alarm call is a rapid "cu-ee."

Breeding

The last confirmed nest was found in 1924 near Tara, Omsk oblast, Siberia. The current status of its breeding is unknown.

Similar Species

The Slender-billed Curlew can be confused with the Eurasian Curlew and the Whimbrel, but careful observation of its distinctive markings and bill shape can aid in correct identification.

Diet and Feeding

Its diet consists of small invertebrates, which it locates by probing mud with its bill. It is also known to feed on other small items when available.

Conservation Status

The Slender-billed Curlew is classified as Critically Endangered and is feared to be extinct, with the last confirmed sighting in 2004. The decline is attributed to excessive hunting and habitat loss, particularly in its wintering grounds. Despite extensive searches, the current breeding status and population dynamics remain uncertain.