great egret

The great egret (''Ardea alba''), also known as the common egret, large egret, or (in the Old World) great white egret or great white heron is a large, widely distributed egret. The four subspecies are found in Asia, Africa, the Americas, and southern Europe. Recently it is also spreading to more northern areas of Europe. Distributed across most of the tropical and warmer temperate regions of the world, it builds tree nests in colonies close to water.

Taxonomy and systematics

Like all egrets, it is a member of the heron family, Ardeidae. Traditionally classified with the storks in the Ciconiiformes, the Ardeidae are closer relatives of pelicans and belong in the Pelecaniformes, instead. The great egret—unlike the typical egrets—does not belong to the genus ''Egretta'', but together with the great herons is today placed in '' Ardea''. In the past, however, it was sometimes placed in ''Egretta'' or separated in a monotypic genus ''Casmerodius''.

The Old World population is often referred to as the "great white egret". This species is sometimes confused with the great white heron of the Caribbean, which is a white morph of the closely related great blue heron.

The scientific name comes from Latin ''ardea'', "heron", and ''alba'', "white".

Subspecies

Four subspecies are found in various parts of the world, which differ but little. Differences among them include bare-part coloration in the breeding season and size. The smallest subspecies, ''A. a. modesta'', is from Asia and Australasia and some taxonomists consider it to be a full species, the eastern great egret (''Ardea modesta''), but most scientists treat it as a subspecies.

* ''A. a. alba'' Linnaeus, 1758 – nominate, found in Europe and across the Palearctic.
* ''A. a. egretta'' Gmelin, JF, 1789 – found in the Americas
* ''A. a. melanorhynchos'' Wagler, 1827 – found in Africa
* '' A. a. modesta'' Gray, JE, 1831 – eastern great egret, found in India, Southeast Asia, East Asia and Oceania

Description

The great egret is a large heron with all-white plumage. Standing up to tall, this species can measure in length with a wingspan of . Body mass can range from , with an average around . It is thus only slightly smaller than the great blue or grey heron (''A. cinerea''). Apart from size, the great egret can be distinguished from other white egrets by its yellow bill and black legs and feet, though the bill may become darker and the lower legs lighter in the breeding season. In breeding plumage, delicate ornamental feathers are borne on the back. Males and females are identical in appearance; juveniles look like nonbreeding adults. Differentiated from the intermediate egret (''Ardea intermedia'') by the gape, which extends well beyond the back of the eye in case of the great egret, but ends just behind the eye in case of the intermediate egret.

It's flight is slow with its neck retracted. This is characteristic of herons and bitterns, and distinguishes them from storks, cranes, ibises, and spoonbills, which extend their necks in flight. The great egret walks with its neck extended and wings held close. The great egret is not normally a vocal bird; it gives a low, hoarse croak when disturbed, and at breeding colonies, it often gives a loud croaking ''cuk cuk cuk'' and higher-pitched squawks.

Owing to its wide distribution across so much of the Americas, as well as Africa, Europe and Asia, the great egret shares its habitat with many other similar species. For example, the little egret (''Egretta garzetta''), intermediate egret (''Ardea intermedia''), Chinese egret (''Egretta eulophotes''), and the western reef heron (''Egretta gularis''). In the Americas, the snowy egret (''Egretta thula'')—a medium-sized heron that shares the same habitat as the great egret—is one such species. The snowy egret is readily distinguished from the great egret because it is noticeably smaller, and it has a more slender bill which is black in color and yellow feet, whereas the great egret has a yellow bill and black feet. Another species that—in North America—is easily confused with the great egret is the white morph of the great blue heron (''Ardea herodias''). The great blue heron is a bit larger, and has a thicker bill than that of the great egret.

Distribution and habitat

The great egret is generally a very successful species with a large and expanding range, occurring worldwide in temperate and tropical habitats. It is ubiquitous across the Sun Belt of the United States and in the Neotropics.

Conservation

In North America, large numbers of great egrets were killed around the end of the 19th century so that their plumes, known as " aigrettes", could be used to decorate hats. Numbers have since recovered as a result of conservation measures. Its range has expanded as far north as southern Canada. However, in some parts of the southern United States, its numbers have declined due to habitat loss, particularly wetland degradation through drainage, grazing, clearing, burning, increased salinity, groundwater extraction and invasion by exotic plants. Nevertheless, the species adapts well to human habitation and can be readily seen near wetlands and bodies of water in urban and suburban areas.

The great egret is partially migratory, with northern hemisphere birds moving south from areas with colder winters. It is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

In 1953, the great egret in flight was chosen as the symbol of the National Audubon Society, which was formed in part to prevent the killing of birds for their feathers.

On 22 May 2012, a pair of great egrets was observed nesting in the UK for the first time at the Shapwick Heath nature reserve in Somerset. The species was a rare visitor to the UK and Ben Aviss of the BBC
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