common name for terrestrial, Old World birds in the family Burhinidae. The name derives from the bird's thickened tarsal joints. Thick-knees are shy, solitary birds. They are rapid runners with long legs and partially webbed feet, which lack a hind toe. The wings may be long and pointed, or short and rounded, according to species. Generally they fly fast and low but only for short distances. In body length, thick-knees range from 14 to 20 in. (36–51 cm). Members of the genus Burhinus
are among the smaller species. Their straight, stout bills are shorter than their heads. Thick-knees of the genus Orthorhamphus
have massive bills considerably larger than their heads, while those of the genus Esacus
are compressed and slightly upturned. Thick-knees are widely distributed throughout a range of temperate and tropical habitats including shore, scrub, desert, and savanna, but typically in somewhat open country. Their colorations vary with their backgrounds, usually dull gray-brown with darker streaks. They are nocturnal birds, with large, owllike eyes. Their diet consists of a wide range of animals and plants, including insects, small mammals, seeds, and, occasionally, other birds. Their alternate name of stone curlew probably derives from their habit of laying their large eggs directly on bare, stony ground. The eggs range in color from cream to brown, with various darker markings according to local soil colors. Both sexes participate in incubation, and the highly precocious chicks are able to leave the nest almost immediately upon hatching. Thick-knees are classified in the phylum Chordata
, subphylum Vertebrata, class Aves, order Charadriiformes, family Burhinidae.