Taxonomy
There are two subfamilies: the Bucorvinae contain the 2 ground-hornbills in a single genus, whereas the Bucerotinae contain all other taxa. Traditionally they are within the order Coraciiformes (which includes also kingfishers, rollers, hoopoes and bee-eaters). In the Sibley-Ahlquist taxonomy, however, hornbills are separated from the Coraciiformes and make an order of their own, Bucerotiformes, with the subfamilies elevated to family level. Given that they are almost as distant from the rollers, kingfishers and allies as are the trogons, the arrangement chosen is more a matter of personal taste than any well-established taxonomic practice. All that can be said with reasonable certainty is that placing the hornbills outside the Coraciiformes and the trogons inside would be incorrect.
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