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Swift (bird)

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Swifts
Chimney Swift
Scientific classification
Kingdom:
Phylum:
Class:
Order:
Family:
Apodidae

Hartert, 1897
Genera

Many; see text.

The swifts are birds superficially similar to swallows but are actually not closely related to those passerine species at all; swifts are in the separate order Apodiformes, which they formerly shared with the hummingbirds.

The resemblances between the swifts and swallows are due to convergent evolution reflecting similar life styles based on catching insects in flight.

The family scientific name comes from the Greek απους, apous, meaning "without feet", since swifts have very short legs and never settle voluntarily on the ground, perching instead on vertical surfaces. The tradition of depicting swifts without feet continued into the Middle Ages, as seen in the heraldic martlet.

Swifts are the most aerial of birds and some, like the Common Swift, even sleep and mate on the wing. Larger species, such as white-throated needletail, are amongst the fastest flyers in the animal kingdom. One group, the Swiftlets or Cave Swiftlets have developed a form of echolocation for navigating through dark cave systems where they roost. One species, Aerodramus papuensis has recently been discovered to use this navigation at night outside its cave roost also.

Like swallows and martins, the swifts of temperate regions are strongly migratory and winter in the tropics.

Many swifts have a characteristic shape, with a short forked tail and very long swept-back wings that resemble a crescent or a boomerang. The flight of some species is characterised by a distinctive "flicking" action quite different from swallows.

The nest of many species is glued to a vertical surface with saliva, and the genus Aerodramus use only that substance, which is the basis for bird's nest soup.

Systematics and evolution

The treeswifts are closely related to the true swifts, but form a separate family, the Hemiprocnidae.

In the Sibley-Ahlquist taxonomy, the old order Apodiformes is split. Swifts remain in that order, but hummingbirds are put into a new order, Trochiliformes. This might be correct, but further research on the interrelationships and evolutionary history of the Apodiformes is necessary.

The taxonomy of this group is in general complicated, with genus and species boundaries widely disputed, especially amongst the swiftlets. Analysis of behavior and vocalizations is marred by common parallel evolution, while analyses of different morphological traits and of various DNA sequences have yielded equivocal and partly contradictory results (Thomassen et al., 2005).

The Apodiformes diversified during the Eocene, at the end of which the extant families were present; fossil genera are known from all over temperate Europe, between today's Denmark and France, such as the primitive Scaniacypselus (Early - Middle Eocene) and the more modern Procypseloides (Late Eocene/Early Oligocene - Early Miocene). A prehistoric genus sometimes assigned to the swifts, Primapus (Early Eocene of England), might also be a more distant ancestor.

Species list: Family Apodidae

Tribe Cypseloidini

Tribe Collocaliini - swiftlets

Tribe Chaeturini - needletails

Tribe Apodini - typical swifts

References

  • Chantler, Phil & Driessens, Gerald (2000): Swifts : a guide to the swifts and treeswifts of the world. Pica Press, Mountfield, East Sussex. ISBN 1-873403-83-6
  • Thomassen, Henri A.; Tex, Robert-Jan; Bakker, Merijn A.G. & Povel, G. David E. (2005): Phylogenetic relationships amongst swifts and swiftlets: A multi locus approach. Molecular Phylogenetics and Evolution 37(1): 264-277. doi:10.1016/j.ympev.2005.05.010 (HTML abstract)