are the long-legged freshwater and coastal birds
in the family Ardeidae
, with 64 recognised species
, some of which are referred to as egrets
rather than herons. Members of the genera Botaurus
are referred to as bitterns, and, together with the zigzag heron
or zigzag bittern in the monotypic genus Zebrilus
, form a monophyletic
group within the Ardeidae. Egrets are not a biologically distinct group from the herons, and tend to be named differently because they are mainly white or have decorative plumes. Although egrets have the same build as herons, they tend to be smaller. Herons, by evolutionary adaptation, have long beaks.
The classification of the individual heron/egret species is fraught with difficulty, and no clear consensus exists about the correct placement of many species into either of the two major genera, Ardea
. Similarly, the relationships of the genera
in the family are not completely resolved. However, one species formerly considered to constitute a separate monotypic
family, the Cochlearidae or the boat-billed heron
, is now regarded as a member of the Ardeidae.