Most members of this almost worldwide group breed colonially in trees, building large stick nests. Northern species such as Great Blue, Grey and Purple Herons may migrate south in winter, although the first two do so only from areas where the waters freeze.
These are powerful birds with large spear-like bills, long necks and long legs, which hunt by waiting motionless or stalking their prey in shallow water before seizing it with a sudden lunge. They have a slow steady flight, with the neck retracted as is characteristic of herons and bitterns; this distinguishes them from storks, cranes, and spoonbills, which extend their necks.
Some members of Ardea are clearly very closely related, such as the Grey, Great Blue, and Cocoi Herons, which form a superspecies. However, the Great Egret, in particular, has been placed in other genera by various authors as Egretta alba and Casmerodius alba. Nevertheless, this species closely resembles the large Ardea herons in everything but colour, whereas it shows fewer similarities to the smaller white egrets.
The Great Blue Heron (Ardea herodias) is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North America and Central America as well as the Caribbean and the Galápagos Islands. It is a rare vagrant to Europe, with records from Spain, the Azores, England and the Netherlands. An all-white population found only in the Caribbean and southern Florida was once treated as a separate species and known as the Great White Heron.