The tree kingfishers or wood kingfishers, familyHalcyonidae, are the most numerous of the three families of birds in the kingfisher group. There are between 56 and 61 species of tree kingfisher in around 12 genera, and include several species of kookaburras. The kingfishers are quite well-known: the vagueness of the counts reflects controversies in the taxonomy of this family more than any gross lack of data on the birds themselves; the present arrangement of genera seems to be well warranted by molecular analyses, although the relationship of many genera to one another is still unresolved (Moyle, 2006) [1]
The family appears to have arisen in Indochina and the Malay Archipelago and then spread to many areas around the world. Tree kingfishers are widespread through Asia and Australasia, but also appear in Africa and the islands of the Pacific and Indian Oceans.
^ Moyle, Robert G. (2006): A Molecular Phylogeny of Kingfishers (Alcedinidae) With Insights into Early Biogeographic History. Auk123(2): 487–499. HTML fulltext (without images)