Cattle Egret

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Image:Cattleegret.jpg

Common Name: Cattle Egret
Scientific Name: Bubulcus ibis

Size: 20 inches (50 cm)

Habitat: Worldwide; in the tropics, the subtropics and warm temperate zones (wherever there is livestock).

Status: Least Concern. Global Population: 3,800,000 - 7,600,000. This species has a large range, with an estimated global extent of occurrence of 10 million square km (3.8 square miles). Its global population estimated to be 3.8–6.7 million individuals. The expansion and establishment of the species over large ranges has led it to be classed as an invasive species (although little, if any impact has been noted yet).

Diet: Mostly insects found on domestic livestock; particularly flies (adults and maggots), ticks, grasshoppers, crickets and moths, as well as spiders, frogs, and earthworms. Cattle Egrets sometimes feed in shallow water but are typically found in fields and dry grassy habitats, reflecting its greater dietary reliance on terrestrial insects rather than aquatic prey.

Nesting: The sexes are similar, but the male is marginally larger and has slightly longer breeding plumes than the female; juvenile birds lack colored plumes and have a black bill.

They nests in colonies, which are usually found in woodlands near lakes or rivers, in swamps, or on small inland or coastal islands. These nesting areas are sometimes shared with other wetland birds such as herons, egrets, ibises and cormorants. The breeding season varies; within South Asia and northern India nesting begins with the onset of monsoons in May. The breeding season in Australia is November to early January, with one brood laid per season.The North American breeding season lasts from April to October.

The male displays in a tree in the colony, using an range of ritualized behaviors such as shaking a twig and sky-pointing (raising bill vertically upwards), and the pair forms over three or four days. A new mate is chosen in each season and when re-nesting following nest failure. The nest is a small untidy platform of sticks in a tree or shrub constructed by both parents. Sticks are collected by the male and arranged by the female, and stick-stealing is rife. The clutch size can be anywhere from one to five eggs, although three or four is most common. The pale bluish-white eggs are oval-shaped. Incubation lasts around 23 days, with both sexes sharing incubation duties. The chicks are partly covered with down at hatching, but are not capable of fending for themselves; they become endothermic at 9–12 days and fully feathered in 13–21 days. They begin to leave the nest and climb around at 2 weeks, fledge at 30 days and become independent at around the 45th day.

Cool Facts: The Cattle Egret is a popular bird with cattle ranchers for its perceived role as a biocontrol of cattle parasites such as ticks and flies. A study in Australia found that Cattle Egrets reduced the number of flies that bothered cattle by pecking them directly off the skin.

The massive and rapid expansion of the Cattle Egret's range is due to its relationship with humans and their domesticated animals. Originally adapted to a symbiotic relationship with large browsing animals, it was easily able to switch to domesticated cattle and horses. As livestock keeping spread throughout the world it was able to occupy otherwise empty niches such as in various sub-Antarctic islands, including South Georgia, Marion Island, the South Sandwich Islands and the South Orkney Islands. A small flock of eight birds was also seen in Fiji in 2008.

In addition to the natural expansion of its range, Cattle Egrets have been introduced into a few areas. The species was introduced to Hawaii in 1959, and to the Chagos Archipelago in 1955. Successful releases were also made in the Seychelles and Rodrigues, but attempts to introduce the species to Mauritius failed. Numerous birds were also released by Whipsnade Zoo in England, but the species never established.


Found in Songbird ReMix Shorebirds Volume I

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