THE CATTLE EGRET

(Bubublus ibis)

The Cattle Egret (Bubulbus ibis) is a non indigenous species to the south east of United States. This bird is native to the Old World from Africa to India and presumably "invaded" North America in the late nineteenth century. [Cattle Egret] Interestingly this bird is the smallest and most widely distributes egret species in the world (Forbush, 1939). Since its exodus to North America, the Cattle Egret population has thrived. This is most likely due to the lack of natural predators and relatively little competition from other species in their community. [Texas A&M - Cattle Egrets]

Perhaps the most interesting aspect of Cattle Egret biology is their feeding behavior. As suggested by their common name, the cattle egret lives in a commensalistic relationship with cattle. These birds feed by following cattle around pastures and feeding on the insects raised by the cattle. The insects that they feed on include beetles, grasshoppers, flies and even ticks of the backs of cows. It has even been discovered that cattle egrets consume up to six hundred insects a day; equal to half of their body weight. [Cattle Egret] These insects are "stirred up" by the shuffling of the feet of the cattle. The amazing abundance and expansive colonization of North America by the Cattle Egret is thought to be the result of the world wide boom in intensive cattle farming and the creation of habitat for Cattle Egrets in cleared field for agriculture and development. [NWF - Int'l Wildlife Magazine - African Egrets]

The other reason for the expansive success of the Cattle Egret relative to other egrets and herons may be attributes to the fact that Cattle Egrets do not require water and wetland habitat for nesting.[NWF - Int'l Wildlife Magazine - African Egrets] More typically Cattle Egret are more limited by the availability of habitat with an adequately abundant insect populations.

It is thought that this interesting bird evolved with wild grazing animals in Africa [McCann Book Chapter 4] As human infringement on natural habitat has increased, the Cattle Egret has easily adapted to the new habitats created by increased agriculture. This species has benefited from human agricultural endeavors and exploited the new habitat created by these practices. Cattle Egrets have been seen foraging behind other large animals (such as horses, bison, buffalo, etc.), behind worker cutting sugar cane, behind bulldozers in city dumps, and even on highways eating insects that have been knocked down by passing cars. Cattle Egrets feed behind any animal (or machine!) that travels slow enough so that the egrets can follow closely behind the "host" and prey upon the insects that are stirred up by the movement. [NWF - Int'l Wildlife Magazine - African Egrets] These opportunistic egrets have been tremendously successful and have adapted to the new environment and habitat changes created by human practices.

At nightfall, Cattle Egrets leave the pastures where they feed and spend most of their day and fly to roost. [Cattle Egret] Cattle Egrets do sometimes compete for nesting areas and nest materials with other egrets, those native to North America. [NWF - Int'l Wildlife Magazine - African Egrets] They have also affected the feeding behaviors of other species including the Little Blue Heron who have learned to follow the Cattle Egret in to the cattle pastures and feed behind the cows.

There is some concern about the prolific expansion of the Cattle Egret to the New World. While the competition between native herons and Cattle Egrets seems to be of little importance, Cattle Egrets do feed, on occasion, on the eggs and nestlings of ground-nesting birds. [USFWS - Wading Bird Habitats] Therefore, there are conservation issues revolving around the expansion of the Cattle Egret population that can be presumably attributed to the creation of suitable habitat by human practices.

Cattle Egrets are the smallest of all Egrets. It is only about fifty centimeters in length. It is all white in color except during breeding season when yellow/orange plumes appear around the head neck and back .[Cattle Egret] This bird is interesting in it adaptability, feeding behavior, expansive migration and possible ecological impacts on other species.

Works Cited:

Forbush, E.H., Natural History of The Birds of Eastern and Central North America. Cambridge, Mass., 1939.