Compared with other herons, Western Cattle Egrets are noticeably small and compact. They have relatively short legs and a short thick neck. The straight, daggerlike bill is shorter and thicker than other herons. They have medium-length, broad, rounded wings.
Adult Western Cattle Egrets are all white with a yellow bill and legs. In breeding plumage they have golden plumes on their head, chest, and back. Juveniles have dark legs and bill.
Western Cattle Egrets stalk insects and other small animals on the ground in grassy fields. They are much less often seen in water than other herons. They nest in dense colonies of stick nests in trees or emergent wetlands, often mixed with other species of herons.
They forage in flocks in upland areas such as pastures and fields, generally focusing on drier habitats than other species of white herons.
This species began its remarkable range expansion in the late 19th century: spreading across the African continent, Madagascar and the Comoro Islands from 1900; into southern France and the Volga Delta in the 1950s; and, in the Americas, northeastern South America in the late 19th century, the Antilles in the mid-1950s, most of South America between the 1940s and 1970s, and Central and North America between the early 1950s and early 1970s. Its rapid expansion is well documented and studied, encouraging speculation about which aspects of its life history and ecology have most favoured the growth of its range and numbers. Indeed, this uncommon bird has provided a rare opportunity for global-scale comparative studies of its population dynamics and interactions with native colonial waterbirds as well as people.
Of particular interest are the economic aspects of the species' feeding habits and diet, medical and veterinary concerns, breeding colonies considered nuisances, and its status as a bioindicator of environmental conditions. The apparent keys to its spread and success are its dispersing tendencies, gregariousness, diet, adaptability to foraging - especially as humans convert ever larger tracts of landscape to pasture for livestock production and crop fields for rice agriculture - and its reproductive adaptability and success. Although numerous studies have been conducted in many parts of the world, data for its study in its original range are lacking.
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