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Bubulcus ibiscattle egret

By Alicia Ivory

Geographic Range

The cattle egret, due to its great range expansion in association with cattle ranching, has become a true 'cosmopolitan' species. It occurs in North America, generally not in the west or far north; and Eurasia, though usually not in the east. It also inhabits Africa, Australia and parts of South America. Cattle egret are native to Africa and southern Spain. (Hancock and Elliott, 1978)

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. (Telfair, 1994)

Physical Description

The cattle egret is a medium sized bird, with a 'hunched' posture, even when it is standing erect. In comparison to other egrets, it is short-legged and thick-necked. The total length of the bird ranges from 46-56 cm, and its wingspan averages 88-96 cm. The basic plumage of the adult of both sexes is pure white, with a dull orange or yellow bill, and dull orange legs. For a brief period of time during the breeding season, however, the plumage of the breeding adults is buffy at the head, neck and back, and the eyes, legs and bill are a vivid red. Because of this coloration, it is sometimes called the Buff-Backed Heron. (Telfair, 1994; Hancock and Elliott, 1978; http://www.coos.or.us/~aigrette/ce.htm; http://www.mbr.nbs.gov/id/htmid/h2001id.html)

  • Average mass
    220 g
    7.75 oz
    AnAge

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. (Telfair, 1994; http://www.coos.or.us/~aigrette/ce.htm)

  • Average eggs per season
    3
    AnAge
  • Average time to hatching
    22 days
    AnAge

Lifespan/Longevity

Behavior

The cattle egret is very gregarious and can be easily identified by its tendency to associate closely with grazing animals. It tends to roost in large colonies, usually with other species of colonial waterbirds. It is strongly migratory. However, distinguishing between migration and dispersal in cattle egrets is very difficult because they have a tendency to wander extensively. It often flocks with other ardeids during migration. They also fly in flocks to and from feeding, breeding, and roosting sites. In flight, it tucks its neck in close to its body, or holds it in an S-shape. Even at rest, the neck is rarely extended. It walks in a swaying manner, much like a goose. Some individuals may 'leapfrog' over one another while moving across the feeding area. It is capable of evasive manuvers and usually doesn't swim unless it is pursued. The cattle egret is usually silent when it is away from its roost, and it has no special flocking or flight calls. It gives most calls at the breeding colony, and its voice is a simple, husky, quiet 'rick-rack.' Individuals defend their perch sites. Outside of the breeding season, there is little aggressive behavior, but during the breeding season, encounters are intense. The erection of the crest is indicative of the bird's level of antagonism. At the colony site, the male may defend one or two territories. After pairs are formed, together both members defend the nesting territory. There is no territorialism at the feeding sites, as they feed almost exclusively in flocks. (Telfair, 1994; http://mbr.nbs.gov/id/htmid/h2001id.html)

Communication and Perception

Food 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. (Telfair, 1994; Hancock and Elliott, 1992)

Economic Importance for Humans: Positive

Some ranchers rely on cattle egrets for fly control more than they do pesticides.

Economic Importance for Humans: Negative

Cattle egrets may transmit parasites and other disease organisms to livestock and people, but this is very speculative. Some heronries are considered nuisances when near structures used by humans due to noise, odor, concern over health hazards, and potential danger to aircraft. (Telfair)

Conservation Status

The cattle egret is the most plentiful ardeid in many areas of the U.S. Its range continues to expand as a result of widespread landscape conversion to pasturelands, where these birds forage with cattle. (Telfair, 1994)

Other Comments

The cattle egret now outnumbers the combined populations of all other egrets and herons found in North America. No other egret spends as little time near water than does the cattle egret. ( http://www.coos.or.us/~aigrette/ce.htm)

It is sometimes called by names of the animal it associates with, such as Elephant Bird, Rhinoceros Egret, or Hippopotomus Egret.

Three subspecies are recognized: B. i. ibis, B. i. seychellarum, and B. i. coromanda. (Telfair, 1994)

Contributors

Alicia Ivory (author), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

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Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

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oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Hancock, J. and H. Elliot. The Herons of the World. Harper and Row Publishing, New York, 1978.

Telfair, R.C. II. 1994. Cattle Egret (Bubulcus ibis). In The Birds of North America, No. 113 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.

http://www.coos.or.us/~aigrette/ce.htm

http://www.mbr.nbs.gov/id/htmid/h2001id.html

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