Cattle Egret (Bubulcus ibis)
Manta Rota, Faro, Portugal
[order] Ciconiiformes | [family] Ardeidae | [latin] Bubulcus ibis | [UK] Cattle Egret | [FR] Héron garde-boeufs | [DE] Kuhreiher | [ES] Garza Ganadera | [IT] Airone guardabuoi | [NL] Koereiger
spanwidth min.: 82 cm
spanwidth 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.: 32 days
eggs min.: 3
eggs max.: 8
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).
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.
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.
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
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.
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.