These are all specialist fish-eating species, unlike many representatives of the other two families, and it is likely that they are all descended from fish-eating kingfishers which founded populations in the New World. It was believed that the entire group evolved in the Americas, but this seems not to be true. The original ancestor possibly evolved in Africa - at any rate in the Old World - and the Chloroceryle species are the youngest ones.
Not longer than 5 million years ago - possibly as recently as 2.9 million years ago -, an Old World giant kingfisher became the ancestor of the Belted and Ringed Kingfishers, and later, another species related to the Pied Kingfisher became the ancestor of the Chloroceryle green kingfishers after colonizing the Americas. While the evolutionary history of the Water Kingfishers in regard to their internal relationships is well resolved, it is not entirely clear whether they evolved from river kingfishers or tree kingfishers, and whether they immigrated across the Atlantic or the Pacific Ocean (though the former seems more likely).
There are 9 water kingfisher species in three genera:
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 Australasia. 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. In Britain, the word 'kingfisher' normally refers to the Common Kingfisher.