Cattle egret

The cattle egrets (formerly genus Bubulcus) are a cosmopolitan clade of herons (family Ardeidae) in the genus Ardea found in the tropics, subtropics, warm temperate, and increasingly in cooler temperate zones. As currently treated, the clade contains two species, the western cattle egret and the eastern cattle egret, although some authorities (particularly in the past) regarded them as a single species. Despite the similarities in plumage to the egrets of the genus Egretta, they have recently been found to be genetically embedded within the genus Ardea, and are now included there. Originally native to parts of Asia, Africa, and southernmost Europe, the two species have undergone rapid expansion in their distribution and have successfully colonised much of the rest of the world in the last century.

They are white birds adorned with buff plumes in the breeding season. They nest in colonies, usually near bodies of water and often with other wading birds. The nest is a platform of sticks in trees or shrubs. Cattle egrets exploit drier and open habitats more than other heron species. Their feeding habitats include seasonally inundated grasslands, pastures, farmlands, wetlands, and rice paddies. They often accompany cattle or other large mammals, catching insect and small vertebrate prey disturbed by these animals. Some populations are migratory and others show postbreeding dispersal.

Adult cattle egrets have few predators, but birds or mammals may raid their nests, and chicks may be lost to starvation, calcium deficiency, or disturbance from other large birds. Cattle egrets maintain a special relationship with cattle, which extends to other large grazing mammals; increased human livestock farming is believed to be a major cause of their suddenly expanded range. Cattle egrets remove ticks and flies from cattle and consume them. This benefits both organisms, but it has been implicated in the spread of tick-borne animal diseases.

Before the description of the Bubulcus by Charles Lucien Bonaparte in 1855, the western cattle egret had already been described in 1758 by Carl Linnaeus in his Systema Naturae as Ardea ibis, while the eastern cattle egret was described in 1783 by Pieter Boddaert as Cancroma coromanda. Their former generic name Bubulcus is Latin for herdsman, referring, like the English name, to their association with cattle. The species name ibis is a Latin and Greek word which originally referred to another white wetland bird, the sacred ibis, but was applied to the western cattle egret in error. The epithet coromanda refers to the Coromandel Coast of India.

The eastern and western cattle egrets were first split by McAllan and Bruce in 1988, but were regarded as conspecific by almost all other recent authors until the publication of the influential Birds of South Asia. The eastern cattle egret breeds in southern and eastern Asia and Australasia, and the western species occupies the rest of the cattle egret's range, including southwestern Asia, Europe, Africa, and the Americas. According to the IOC birdlist, they are both monotypic species. Some authorities have recognised a third taxon in the Seychelles, A. i. seychellarum, which was first described by Finn Salomonsen in 1934, but this is now considered synonymous with typical A. ibis.

Despite superficial similarities in appearance, the cattle egret is more closely related to the other members of the genus Ardea, which comprises the great or typical herons and the great egret (A. alba), than to the majority of species termed egrets in the genus Egretta. Rare cases of hybridisation with little blue herons (Egretta caerulea), little egrets (E. garzetta), and snowy egrets (E. thula) have been recorded.

An older English name for cattle egrets is buff-backed heron.

The cattle egrets are stocky herons with a wingspan of 88–96 cm (34+1⁄2–38 in); they are 46–56 cm (18–22 in) long, and weigh 270–512 g (9+1⁄2–18 oz). They have a relatively short, thick neck, a sturdy bill, and a hunched posture. The nonbreeding adults have mainly white plumage, a yellow bill, and greyish-yellow legs. During the breeding season, adults of the western cattle egret develop orange-buff plumes on the back, breast, and crown, and the bill, legs, and irises become bright red for a brief period prior to pairing. The sexes are similar, but the male is marginally larger and has slightly longer breeding plumes than the female. Juvenile birds lack coloured plumes and some have a black bill briefly after fledging. Birds in the Seychelles, argued by some to be a valid subspecies A. i. seychellarum, were first reported to be smaller and shorter-winged than the other forms, but are not outside the range of variation found elsewhere in western cattle egret, particularly in eastern Africa. They also have white cheeks and throat, like A. ibis; the nuptial plumes, first reported to be golden as in A. coromanda, are also within the range of variation in typical A. ibis, and less extensive than in A. coromanda.