The water kingfishers or Cerylidae are one of the three families of kingfishers, and are also known as the cerylid kingfishers. All six American species are in this family.
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: