Boyd’s Bible Dictionary:
An unclean bird, thought to be the beautiful migratory hoopoe
Concise Bible Dictionary:
Hoopoe
This is generally supposed to refer to the Hoopoe, which rendering the RV has adopted. It is judged to be the Upupa epops. It feeds upon all sorts of insects, and its nest has a very unpleasant smell, either of which facts would be a sufficient reason for its being classed among the unclean birds (Lev. 11:1919And the stork, the heron after her kind, and the lapwing, and the bat. (Leviticus 11:19); Deut. 14:1818And the stork, and the heron after her kind, and the lapwing, and the bat. (Deuteronomy 14:18)). It has a conspicuous crest on its head, which it seems proud of displaying.