The Herons are
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 in
breeding plumage. 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.
Although herons
resemble birds in some other families, such as the storks, ibises, spoonbills,
and cranes, they differ from these in flying with their necks retracted,
not outstretched. They are also one of the bird groups that have powder
down. Some members of this group nest colonially in trees, while
others, notably the bitterns, use reed beds. A group of them is called a siege.