Cattle egret (Bubulcus ibis)
|Also known as:||Buff-backed heron|
|Synonyms:||Ardea ibis, Ardeola ibis|
|Size||Length: 46 – 56 cm (2)|
Wingspan: 88 – 96 cm (2)
Male weight: 390 g (3)
Female weight: 340 g (3)
Classified as Least Concern (LC) on the IUCN Red List (1) and listed on Appendix III of CITES (4).
The only species in its genus, the cattle egret gains its common name from its habit of commonly wandering alongside herds of cattle. It is stocky in build, has a slightly hunched posture and white-grey plumage. In the breeding season, the feathers on the head and back turn an orange-red and, remarkably, the irises and bill turn the same orange-red. The sexes differ in size and appearance, but only slightly (3); the male is marginally larger and has longer breeding plumes during the mating season. The cattle egret is generally a quiet bird; however, it can sometimes give a coarse, throaty call, especially during the mating season (3).
The cattle egret has an incredibly large range and can be found nesting in North America, South America, Europe, Africa, Asia and Australia (5). Remarkably, this bird has not always been found across all these regions; it is believed to have originated in central Africa and then spread to many other parts of the world during the 19th century as human activities, such as the expansion of agriculture and the cattle industry, created suitable habitat for this species (3).
The cattle egret is found in open, grassy areas, such as pastures, meadows, marshes, flood plains and swamps. The species has a preference for freshwater and is rarely found near marine environments (6).
The cattle egret is an opportunistic feeder, with a diet that consists mainly of a variety of insects, spiders, frogs and worms. It follows large grazers such as plains zebras (Equus quagga) and water buffalos (Bubalus bubalis) to find its meals more quickly (7); when a grazer pulls up grass to eat, it also exposes organisms in the soil below. These are easy pickings for the egret and as the bird does not hinder the grazer, the relationship is a successful one. The cattle egret can also forage for food by itself without aid from grazers but the process is much slower and requires more energy (3).
Breeding generally takes place near water sources and in colonies, and starts with males competing with each other using animated sexual displays. If a male is successful in finding a mate, the pair will produce one brood for the season, laying between one and five eggs in a nest made from sticks that the male has collected and the female has arranged. The males will find a new mate each season (3). Studies have shown that there is intense sibling rivalry over food and more aggressive chicks tend to prevail, sometimes even resulting in the weakest chick dying of starvation (8).
This species of egret is described as a ‘partially’ migratory bird (6); whether a group will migrate depends on the climate and the food availability in the area. In the northern hemisphere the cattle egret tends to migrate from cooler to warmer climates in the winter, and return in the summer when temperatures increase. In Australasia, the cattle egret travels from mainland Australia to New Zealand and Tasmania between February and April, and remains there until October or November (9).
Whilst the cattle egret is, globally, an abundant and widespread species (5), this bird still faces threats in some parts of its range. It has a tendency to form large colonies in and around towns and villages, and the resulting smell and noise means that this species is often considered a public nuisance, resulting in pressure to remove it (5). Within its breeding range, the drainage of lakes for irrigation and the construction of hydroelectric power plants can result in the degradation and destruction of suitable wetland habitats (6). In addition, as a result of the cattle egret feeding from agricultural fields, the consumption of pesticides and other contaminants may be having an adverse affect in some areas (6).
As this bird has a large range and population numbers are believed to have increased over the past century throughout Africa, South West Europe, South and East Asia, the cattle egret is currently of little conservation concern (6) (10).
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- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
IUCN Red List (March, 2010)
Cornell Lab of Ornithology: All About Birds (November, 2009)
- McKilligan, N. (2005) Herons, Egrets and Bitterns, Their Biology and Conservation in Australia. CSIRO Publishing, Collingwood, Australia.
CITES (March, 2010)
- Kushlan, J.A. and Hancock, J.A. (2005) Herons. Oxford University Press, Oxford.
BirdLife International (March, 2010)
- Burger, J. and Gochfeld, M. (1993) Making foraging decisions: host selection by cattle egrets Bulbicus ibis. Ornis Scandinavica, 24(3): 229-236.
- Fujioka, M. (1985) Food delivery and sibling competition in experimentally even-aged broods of the cattle egret. Behavioral Ecology and Sociobiology, 17(1): 67-74.
- Bridgman, H.A., Maddock, M. and Geering, D.J. (1998) Assessing relationships between cattle egret migration and meteorology in the southwest Pacific: a review. International Journal of Biometeorology, 41(4): 143-154.
- del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Volume 1: Ostrich to Ducks.Lynx Edicions, Barcelona.