Portal de Periódicos da CAPES

Factors Affecting Feeding Rates of Anis

1953; Oxford University Press; Volume: 70; Issue: 1 Linguagem: Inglês

10.2307/4081055

1938-4254

Austin Loomer Rand,

Species Distribution and Climate Change

THE Groove-billed Ani, Crotophaga sulcirostris, is a black cuckoo of tropical America. Its habitat is brush and the adjacent grassland and open country. There, usually in small parties, it spends much time walking on the ground, or crawling through the brush looking for its food. This, according to Bent (Life Histories of North American Cuckoos,. . . , U. S. Natl. Mus. Bull. 176: 31, 1940), is largely insects, and to a smaller extent fruit and berries. Frequently anis accompany cattle and mules for the insects these animals frighten into activity. The extent to which anis perch on cattle and pick ticks from them is questioned by Skutch (in Bent, loc. cit.) who suggests the popular belief to this effect is due to confusing the ani with cowbirds which are also black. The ani has also been recorded as following army ants for the insects and other small animals driven from hiding by the ants. They also feed on winged termites, catching them in flycatcher fashion. When in El Salvador from February to July, 1951, working at the Instituto Tropical de Investigaciones Cientificas of the Universidad Autonoma de El Salvador, at San Salvador, I made observations on the feeding rate of the Groove-billed Anis, which demonstrated quantitatively, first, the advantage in their habit of accompanying cows for the insects the cows scared up and, secondly, the increased abundance of their insect food in the wet season. Many of the data that are used below were collected by my son, A. Stanley Rand, who was my assistant in the field. That his data and mine are strictly comparable we demonstrated1 a number of times by both of us watching and recording the activities of the same bird. Anis often feed in shrubbery and about tall grass clumps, where they are difficult to observe, but about San Salvador they also came out onto the grazed open pastures where they were easy to watch. There they had two main methods of feeding. One was by walking about looking for and snapping up insects sitting on the grass. Often the birds would stop and peer, as though near-sighted, at a tuft of grass or at a leaf. Sometimes as insects flew up ahead of a bird they were pursued; sometimes one bird would attempt to take the food from another bird or to seize an insect the other bird had flushed. The second method of feeding on insects in pastures was for the birds to accompany cattle, keeping either by the head or a foot of the grazing beast, and pursuing the insects frightened into activity by the cow. The observations were planned to watch anis feeding without cows for several hours and then with cows for several hours, and to compare