The
Herons are the long-legged freshwater and coastal
birds in the family
Ardeidae, with 64 recognised
species, some of which are referred to as
egrets or
bitterns rather than herons. Members of the genera
Botaurus and
Ixobrychus 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 and
Egretta. 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.