An egret is any of several herons, most of which are white or buff, and several of which develop fine plumes (usually milky white) during the breeding season. Many egrets are members of the genera Egretta or Ardea which contain other species named as herons rather than egrets. The distinction between a heron and an egret is rather vague, and depends more on appearance than biology. The word "egret" comes from the French word "aigrette", referring to the long filamentous feathers that seem to cascade down an egret's back during the breeding season.
Several of the egrets have been moved around from one genus to another in recent years: the Great Egret, for example, has been classified as a member of either Casmerodius, Egretta or Ardea.
In the 19th and early part of the 20th century, some of the world's egret species were endangered by relentless hunting, since hat makers in Europe and the United States demanded massive numbers of egret plumes and breeding birds were killed in locations all around the world.
Several Egretta species, including the Eastern Reef Egret, the Reddish Egret and the Western Reef Egret have two distinct colours, one of which is entirely white. Little Blue Heron has all-white juvenile plumage.