Cook's swift (''Apus cooki'') is a small

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

, superficially similar to a

house martin ''Delichon'' is a small genus of passerine birds that belongs to the swallow family and contains four species called house martins. These are chunky, bull-headed and short-tailed birds, blackish-blue above with a contrasting white rump, and w ...

. It is, however, completely unrelated to those

passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by th ...

species, since

swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIFT, ...

s are in the order Apodiformes. The resemblances between the groups are due to

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

reflecting similar life styles. These birds have very short legs which they use only for clinging to vertical surfaces. The scientific name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

απους, ''apous'', meaning "without feet". They never settle voluntarily on the ground. Blyth's swifts spend most of their lives in the air, living on the insects they catch in their beaks. Cook's swifts breed in limestone caves of

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

and

Indochina Mainland Southeast Asia, also known as the Indochinese Peninsula or Indochina, is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to the west an ...

. The species has a green iridescence, a shallow tail fork and is a short distance migrant. A 2011 study has many taxonomists splitting this species from the fork-tailed swift complex. These swifts build their nests on cliffs, laying 2–3 eggs. A swift will return to the same site year after year, rebuilding its nest when necessary. Cook's swifts are similar in size to

common swift The common swift (''Apus apus'') is a medium-sized bird, superficially similar to the barn swallow or house martin but somewhat larger, though not stemming from those passerine species, being in the order Apodiformes. The resemblances between t ...

, and they are black except for a white rump. They can be distinguished from a partially

leucistic Leucism () is a wide variety of conditions that result in the partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ...

common swift by the deeper tail fork, longer wings, bigger head and larger white throat patch.

References

{{Taxonbar, from=Q1268740 Cook's swift Birds of Myanmar Birds of Thailand Birds of Cambodia Birds of Vietnam Birds of Hainan Cook's swift