Taxonomic name: Bubulcus ibis (Linnaeus, 1758)
Synonyms: Ardea ibis, Ardeola ibis, Bulbucus ibis
Common names: Afrikaanse koereiger, buff-backed heron, cattle egret, depulgabuey, elephant bird, garcilla bueyera (Spanish), garcilla garrapatera, garcita de ganado, garrapatera, garrapatosa, garza de ganado, garza de vaquèra, garza ganadera (Spanish), héron garde-boeufs (French), hippopotomus egret, Indian cattle egret, rhinoceros egret
Organism type: bird
Bubulcus ibis are small stocky herons that associate with grazing species of mammals both domestic and wild. They have strong migratory instincts and disperse thousands of miles in the direction of their choosing. They are, for the most part, self-introduced. They have been observed 'feeding on' native species of birds. They are known to host ticks that could introduce and spread certain tick-borne diseases.
Cattle egrets (Bubulcus ibis) are relatively small, stocky herons, with thick short necks (shorter than body), completely white in colour, except when breeding, at which time they are adorned by orange buff plumes on their crown, back and foreneck. The bill is yellow with a heavy jowl of feathers underneath and the legs are yellow to green and the eyes are light yellow when not breeding. During the breeding season the bill and legs are pink to orange-red and the eyes become a shade of bright red and the lores become purple-pink. Juveniles have black bills. Males and females typically grow to between 51-56cm in length and weigh around 360g (Birds of New Zealand, 2005; Cornell Lab of Ornithology, 2003; and GSMFC, 2005).
Ardea alba, Egretta caerulea, Egretta thula
agricultural areas, estuarine habitats, ruderal/disturbed, urban areas, wetlands
Cattle egrets (Bubulcus ibis) are common around marshes, farms, highway edges, pastures, ploughed fields and other altered habitats. They are strongly migratory and juveniles may disperse thousands of miles in random directions (GSMFC, 2005).
Cattle egrets are able to thrive in areas densly populated by other species, and this makes them potentially able to over-crowd and out-comepete native birds for nesting areas. A number of articles point out however, that cattle egrets seem to have little or no impact on native bird species they live with. They are known to nest next to and amongst native birds with little or no observable conflict occuring, and because their nesting time is after native Herons, this further reduces threat of competition. Lastly, their diet, which is mostly insects and land invertebrates, does not overlap with native Heron's diets, which are fish and aquatic invertebrates. (GSMFC, 2005)
Some ranchers rely on cattle egrets (Bubulcus ibis) for fly control more than they do pesticides (Ivory, 2000).
Native range: Africa, Asia, and Europe (Marion et al. 1993; and GBIF, 2006).
Known introduced range: Australasia-Pacific, North America, South America (Birds of New Zealand, 2005; Bergman et al. 2000; and Bella & Azevedo, 2004).
Introduction pathways to new locations
Natural dispersal: The cattle egret Bubulcus ibis is able to disperse thousands of kilometers in a matter of days through its own migrational patterns and instincts (CAST, 2002).
Cattle egrets (Bubulcus ibis) are opportunistic feeders and typically forage in flocks often associated with grazing animals and pick off parasites on the large herbivores. They may also follow tractors or lawnmowers waiting for insects and other prey items that are flushed out. They feed mostly on relatively large insects, especially grasshoppers, crickets, flies and moths as well as spiders, frogs, crayfish, earthworms, snakes and rarely also fish, birds eggs and even nestling birds. B. ibis also scavenge for edible refuse in garbage dumps. Egrets will fly long distances to catch insects trying to escape fire (Cornell Lab of Ornithology, 2003; and GSMFC, 2005).
GSMFC (2005) reports that, "Bubulcus ibis are promiscuous, with males frequently engaging in extra-pair copulation. They begin to breed at age two or three (Kaufman, 1996). Cattle egrets are colonial breeders, and are frequently found in mixed colonies with other species of herons and egrets. Males establish pairing territories within the colonies and carry out elaborate displays for females. Nests are typically built in aquatic habitats in trees or shrubs of swamps or islands. Nesting materials typically include reeds, shrubs and elder twigs. Males bring most of the material for the nests and females build the nests. Nests are platforms or shallow bowls often with protruding green leafy twigs. Nest building and mating usually lasts three days. Immediately following mating, cattle egrets begin to lose their breeding colours."
Cattle egret (Bubulcus ibis) clutches vary from 1 to 9 pale blue eggs, but typically consist of 3 to 4 eggs. The incubation period can last between 21 and 26 days. Depending on food availability, of the three to four eggs laid, usually only one or two are raised successfully, with later hatching chicks at a decided disadvantage. Young begin to fly in 25-30 days and become independent after about 45 days. B. ibis often nest in colonies with other egrets. Nests are in trees and three white eggs are laid. Both adults incubate and feed chicks by regurgitation. Youngsters scramble onto nearby branches as early as two weeks but do not fly until six or seven weeks of age (Birds of New Zealand, 2005; and GSMFC, 2005).
Reviewed by: Expert review underway: Michel Gauthier-Clerc, Station Biologique de la Tour Du Valat France
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Saturday, 27 September 2008