Slender-billed Curlew

The slender-billed curlew was a small curlew, 36–41 cm (14–16 in) in length with a 77–88 cm (30–35 in) wingspan. It was therefore about the same size as a Eurasian whimbrel, but was more like the Eurasian curlew in plumage. The breeding adult was mainly greyish brown above, with a whitish rump and lower back. The underparts were whitish, heavily streaked with dark brown. The flanks had round or heart-shaped spots. The non-breeding plumage was similar, but with fewer flank spots. Male and females were alike in plumage, but females were longer-billed than males, an adaptation in curlew species that eliminates direct competition for food between the sexes. The juvenile plumage was very similar to the adult, but the flank were marked with brown streaking, the heart-shaped spots only appearing toward the end of the first winter. Compared to the Eurasian curlew, the slender-billed curlew was whiter on the breast, tail, and underwing, and the bill is shorter, more slender, and slightly straighter at the base. The arrowhead-shaped flank spots of the Eurasian curlew also are different from the round or heart-shaped spots of the adults slender-billed. …

The only confirmed breeding records of the slender-billed curlew were a small region of raised bogs north of Omsk, Russia in a period between 1909 and 1925. Isotopic analysis suggests that main breeding range of the species was in a narrow belt in Kazakhstan centered around the 50th parallel north. This area is predominantly steppe, with some areas of forest steppe. In recent history, it mostly migrated to the Mediterranean as well as southern Arabia, with claims in the northern reaches of the Persian gulf, in Kuwait and Iraq. There have been historical records of the bird elsewhere, as in an ornithological dictionary of Gibraltar, written in 1895, it indirectly states that the slender-billed curlew was recorded as a passage migrant in Málaga, Spain.

Little is known about the breeding biology of the slender-billed curlew; however, the few nests that have been observed each contained four eggs. The species fed primarily by probing soft mud with its bill for small invertebrates, but it also picked small prey items from the surface when available. Outside the breeding season, the slender-billed curlew was highly gregarious and often associated with related species, particularly the Eurasian curlew.