Kingfishers are a group of small to medium sized brightly coloured birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species being found in the Old World and Australia. The group is treated either as a single family, Alcedinidae, or as a suborder Alcedines containing three families, Alcedinidae (river kingfishers), Halcyonidae (tree kingfishers), and Cerylidae (water kingfishers). There are roughly 90 species of kingfisher. All have large heads, long, sharp, pointed bills, short legs, and stubby tails. Most species have bright plumage with little differences between the sexes. Most species are tropical in distribution, and a slight majority are found only in forests. They consume a wide range of prey as well as fish, usually caught by swooping down from a perch. Like other members of their order they nest in cavities, usually tunnels dug into the natural or artificial banks in the ground. A few species, principally insular forms, are threatened with extinction.
Taxonomy and evolution
The taxonomy of the three families is complex and rather controversial. Although commonly assigned to the order Coraciiformes, from this level down confusion sets in.
The kingfishers were traditionally treated as one family, Alcedinidae with three subfamilies, but following the 1990s revolution in bird taxonomy, the three former subfamilies are now often elevated to familial level. That move was supported by chromosome and DNA-DNA hybridisation studies, but challenged on the grounds that all three groups are monophyletic with respect to the other Coraciiformes. This leads to them being grouped as the suborder Alcedines.
The tree kingfishers have been previously given the familial name Dacelonidae but Halcyonidae has priority.
The centre of kingfisher diversity is the Australasian region, but the family is not thought to have originated there, instead they evolved in the Northern Hemisphere and invaded the Australasian region a number of times. Fossil kingfishers have been described from Lower Eocene rocks in Wyoming and Middle Eocene rocks in Germany, around 30-40 million years ago. More recent fossil kingfishers have been described in the Miocene rocks of Australia (5-25 million years old). Several fossil birds have been erroneously ascribed to the kingfishers, including Halcyornis, from the Lower Eocene rocks in Kent, which has also been considered a gull, but is now thought to have been a member of an extinct family.
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