Stone-curlew
Thick-knees
are a group of largely tropical birds,in the family Burhinidae.
Despite the group being classed as waders, most species have a preference for arid or semi-arid habitats. They are found worldwide within the tropical zone, with some species also breeding in temperate Europe and Australia.
They are medium to large birds with strong black or yellow black bills, large yellow eyes—which give them a reptilian appearance—and cryptic plumage. The names Thick-knee and Stone-curlew are both in common use, the preference among authorities for one term or the other varying from year to year. The term Stone-curlew owes its origin to the broad similarities with true curlews (which are not closely related).
Thick-knee refers to the prominent joints in the long yellow or greenish legs and apparently originated with a name coined in 1776 for B. oedicnemus, the Thick-kneed Bustard.
They are largely nocturnal, particularly when singing their loud wailing songs, which are reminiscent of true curlews
The diet consists mainly of insects and other invertebrates. Larger species will also take lizards and even small mammals.
Most species are sedentary, but the stone-curlew is a summer migrant in the temperate European part of its range, wintering in Africa.
Breeding
Stone-curlews are migratory, and return to their breeding grounds in England in late March. They nest on open, bare ground or areas with vegetation height below 2 cm.
Arable land or seaside needs to have short or sparse vegetation before being accepted, and is rarely suitable for nesting birds beyond May or June when un managed vegetation becomes too tall. Nests are well spaced.
The birds are monogamous, with pair-bonds thought to be either life-long or annually renewed. They are able to breed at one year of age, but most do not do so until three years old. Most young return to within 15 km of the natal site.
The nest is a scrape on bare stony ground, and is lined with stones, shells, rabbit droppings or pieces of vegetation. Two pale buff randomly marked eggs are laid from April at two day intervals. Both sexes incubate, starting with the second egg for 24-26 days. Chicks normally leave the nest soon after hatching, though can stand and walk properly only on second day.
Parent birds have been observed to carry chicks under their wings for short distances, though this is probably not a common behavior. Both parents tend the chicks and initially provide them with food. The chicks are able to feed themselves a few days later, and fledge at 36-42 days. They become independent only after fledgling.
The breeding season is well spread out, and egg laying can continue as late as August. Up to four replacement clutches can be laid if either eggs or small chicks are lost. Normally one brood is raised, though second broods are regularly seen. The main predators of nests and young are foxes and crows.
The birds will leave England in October. They winter in southern Spain, southwestern France and northwestern Africa.
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