Cattle Egret (Bubulcus ibis)

Cattle Egret

[order] CICONIIFORMES | [family] Ardeidae | [latin] Bubulcus ibis | [authority] Linnaeus, 1758 | [UK] Cattle Egret | [FR] Heron garde-boeufs | [DE] Kuhreiher | [ES] Garza Ganadera | [NL] Koereiger

Subspecies

Monotypic species

Genus

The Cattle Egret (Bubulcus ibis) is a species of heron (family Ardeidae) found in the tropics, subtropics and warm temperate zones. It is the only member of the monotypic genus Bubulcus, although some authorities regard its two subspecies as full species. Despite the similarities in plumage to the egrets of the genus Egretta, it is more closely related to the herons of Ardea. Originally native to parts of Asia, Africa and Europe, it has undergone a rapid expansion in its distribution and successfully colonised much of the rest of the world. Despite superficial similarities in appearance, the Cattle Egret is more closely related to 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.
The Cattle Egret has undergone one of the most rapid and wide reaching natural expansions of any bird species. It was originally native to parts of Southern Spain and Portugal, tropical and subtropical Africa and humid tropical and subtropical Asia. In the end of the 19th century it began expanding its range into southern Africa, first breeding in the Cape Province in 1908. Cattle Egrets were first sighted in the Americas on the boundary of Guiana and Suriname in 1877, having apparently flown across the Atlantic Ocean. It was not until the 1930s that the species is thought to have become established in that area. The species first arrived in North America in 1941 (these early sightings were originally dismissed as escapees), bred in Florida in 1953, and spread rapidly, breeding for the first time in Canada in 1962. It is now commonly seen as far west as California. It was first recorded breeding in Cuba in 1957, in Costa Rica in 1958, and in Mexico in 1963, although it was probably established before that. In Europe the species had historically declined in Spain and Portugal, but in the latter part of the 20th century it expanded back through the Iberian Peninsula, and then began to colonise other parts of Europe; southern France in 1958, northern France in 1981 and Italy in 1985. Breeding in the United Kingdom was recorded for the first time in 2008 only a year after an influx seen in the previous year. In 2008 cattle egrets were also reported as having moved into Ireland for the first time. In Australia the colonisation began in the 1940s, with the species establishing itself in the north and East of the continent. It began to regularly visit New Zealand in the 1960s.

Physical charateristics

Slightly smaller, stockier than Snowy Egret. Breeding plumage shows a wash of buff on crown, breast, and back; little or none at other times. Bill relatively short, yellow (orange-pink on nesting birds). Legs may be yellow, greenish, or coral-pink (on nesting birds), or dusky (immature).

Listen to the sound of Cattle Egret

[audio:http://www.planetofbirds.com/MASTER/CICONIIFORMES/Ardeidae/sounds/Cattle Egret.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 82 cm wingspan max.: 95 cm
size min.: 45 cm size max.: 52 cm
incubation min.: 22 days incubation max.: 26 days
fledging min.: 28 days fledging max.: 26 days
broods: 2   eggs min.: 3  
      eggs max.: 8  

Range

Eurasia, Africa, North America, Latin America : South Europe to Iran, Africa, Indian Ocean Is., North and Latin America.

Habitat

The cattle egret is the most terrestrial heron, being well-adapted to many diverse terrestrial and aquatic habitats. Though it does not depend on aquatic habitats to survive, it does make frequent use of them, even when they are not close to livestock-grazing areas. It is also well-adapted to urban areas. In its breeding range, which is similar to its winter range, it often nests in heronries established by native ardeids.

Reproduction

The cattle egret is seasonally monogamous. It pair-bonds, but at the start of the breeding season there can be a temporary group of 1 male and 2 females. Breeding starts when small groups of males establish territories. Soon after this, aggression increases, and they begin to perform various elaborate courtship displays, attracting groups of females. Immediately before pairing, a female will attempt to subdue the displaying male by landing on his back. Eventually, the male will allow one female to remain in his territory, and within a few hours, the pair-bond is secure. The female then follows the male to another site where the nest will be built. Copulation usually also takes place at this second site. There is little display involved with copulation. Some rapes and rape attempts have been documented. (Telfair, 1994)

Cattle egrets nest is large colonies with other wading birds. Pairs sometimes reuse old nests, or build new ones with live or dead vegetation. They will build in any place that can support a nest. Both sexes participate in nest-building: the female usually builds with materials brought by the male. They often steal sticks and other materials from neighbors’ unattended nests. Material is continuously added to the bulky nests during incubation and after hatching. Throughout mating, nesting, and incubation, a Greeting Ceremony is given whenever one mate returns to the nest to join the other. The Greeting Ceremony involves erection of the back plumes, and flattening of the crest feathers. Eggs are laid every 2 days, and the female does not become attentive to the nest until the last egg is laid. The eggs are light sky blue, turning lighter as time passes. Clutch size is usually 3-4 eggs, although extremes of 1 and 9 have been recorded. Incubation is carried out by both sexes, and lasts 24 days. During the first week, nestlings are easily overheated, and so the parents shade them from the sun beneath their wings. Both parents brood constantly for the first 10 days. The parents may accept chicks from other broods only if they are less than 14 days old. Begging for food becomes very aggressive in days 4-8, and the nestlings are very competative with one another. Siblicide is uncommon, though sibling aggression is strong. Most of the chicks’ growth is completed in the nest, but by 14-21 days, the chicks are capable of leaving the nest and climbing in vegetation, and are thus referred to as ‘branchers.’ At this stage, they remain nearby and continue to beg for food. At 45 days, they are independent, at 50 days they can make short flights, and at around 60 days, they fly to foraging areas.

Feeding habits

It has been calculated that an individual cattle egret can obtain up to 50% more food and use only two-thirds as much energy catching it by associating with cattle, as well as with other large ungulate species. Thus it is a very opportunistic and non-competitive feeder. It commonly associates with livestock, wild buffalo, rhino, elephant, hippo, zebra, giraffe, eland, and waterbuck. Due to their practice of perching on these animals’ backs, cattle egrets are often grouped incorrectly with ‘tick-birds.’ In Australia, they have also been observed to associate with horses, pigs, sheep, fowls, geese, and kangaroos. In the Carribean they even follow the plough, capturing exposed earthworms. The cattle egret’s major prey is active insects which are disturbed by the grazing activities of the cattle egret’s host animals. It eats mostly grasshoppers, crickets, spiders, flies, frogs, and noctuid moths. It is a very active forager, usually feeding in loose aggregations of small or large flocks of mixed sex and age, varying from tens to hundreds of individuals. It may forage in smaller groups or singly. When feeding, it usually walks in a steady strut, followed by a short dart forward, and a quick stab. If they prey animal is small, it is immediately swallowed. If it is larger, it may be jabbed or dipped in water a few times, but it is not dismembered

Video Cattle Egret

httpv://www.youtube.com/watch?v=RVgQq-v1lzM

copyright: youtube


Conservation

This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km2. It has a large global population estimated to be 3,800,000-6,700,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
Bubulcus ibis breeds mainly in Iberia but also patchily elsewhere in southern Europe,
which accounts for less than a quarter of its global breeding range. Its European
breeding population is relatively small (<150,000 pairs), but underwent a large increase between 1970-1990. The stronghold populations in Spain and Portugal continued to increase during 1990-2000, and populations were stable or increased elsewhere in its European range.
The Cattle Egret is a gregarious bird. The species nest in colonies (up to 10 birds to thousands) in trees or in bushes near lakes and ponds, sometimes with other herons. Searching food is collective, in small groups, they take advantage of disturbed insects by cattle. Cattle Egrets also flies in flocks, but unlike geese or other waders known for their strict aligning, they fly in uncoordinated formations. Most of the populaitons are resident, with some dispersion after the breeding season.
Cattle Egret status Least Concern

Migration

Extensive post-breeding dispersal. Many populations in tropical parts of America, Africa and Asia essentially sedentary, with far-reaching dispersive movements in search of suitable feeding conditions, often in connection with rains. In North America, populations of Eeast winter in Central America, West Indies and North South America. Those from South West move mainly towards Mexico. Populations of South West Europe partially migratory, wintering in South Iberian Peninsula and to lesser degree in North Africa. North African breeders fairly sedentary, with some movements South down coast. Birds breeding between Turkey and Caspian Sea apparently migrate to Middle East, Arabia and Iran. Populations of North East Asia migratory: birds ringed in Japan recovered in Philippines; others ringed in Taiwan have turned up in Japan, Philippines, Borneo and Carolinas Islands. Influx for winter noted in Thailand and Malaysia. Australian populations partially migratory, wintering mainly in South East Australia: Tasmania and New Zealand. Some that breed in North West Australia move to South West. Highly prone to vagrancy over long distances, reaching Alaska, Scandinavia, Iceland, many oceanic islands and even Antarctica.

Distribution map

Cattle Egret distribution range map

Literature

Title Age differences in Cattle Egrets Bubulcus ibis foraging with wild ungulates in Kenya
Author(s): Burger J. & Gochfeld M
Abstract: The foraging behavior of adult and juvenile Cattle..[more]..
Source: ARDEA 77 (2): 201-204

download full text (pdf)

Title Extramarital and pair copulations in the Cattle Egret
Author(s): Masahiro Fujioka, Satoshi Yamagishi
Abstract: The copulatory behavior of the Cattle Egret (Bubul..[more]..
Source: The Auk 98: 134-14

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Title CATTLE EGRETS BUBULCUS IBIS AT SEA IN THE SOUTH ATLANTIC OCEAN
Author(s): JOS

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