birds and ants -- 7/29/15

Today's selection -- from What Good are Bugs? by Gilbert Waldbauer. Many birds use ants to kill the parasites that plague them:

"The amazing behaviors by which many birds, including some quail and a multitude of perching birds, use or solicit ants to free their bodies of lice and parasitic mites are known as anting, Birds ant in two quite different ways. Many use the active method of anting, picking up ants with their bills -- usually crushing them -- and wiping them against their plumage to anoint it with ant secretions that are toxic to mites and lice. But a few birds, mainly some crows, thrushes, and finches, use the passive method of anting. They squat or lie on an ant nest and allow the insects to board their bodies and roam, unharmed, through their plumage to search for and destroy external parasites.

"In a brief 1947 note in the journal British Birds, W. Condry described passive anting by an inexperienced, hand-reared carrion crow. He placed it on the ground near a large slab of stone under which there was a horde of ants. After he turned over the stone, the crow immediately became obviously excited. It hesitated for a few seconds but then 'stepped into the middle of the swarming ants ... When some of the ants found their way via his legs to his feathers. the bird showed apparent pleasure and slowly settled down among the ants like a brooding hen, with wings outspread and tail fanned.' Then, in Condry's words, it acted as if 'swooning,' slumping down and lowering its head until it was flat against the ground. Condry concluded that his crow's behavior was innate, programmed in the genes. After all, it had never before seen an ant or another bird anting.

A black drongo in a typical anting posture

"Active anting coats the plumage with noxious secretions. In fact, birds use only ants that secrete formic acid or other toxic fluids. In an article in the Wilson Bulletin, Leon Kelso and Margaret Nice wrote that, in a little-known article in Russian, Vsevolod Dubinin reported that he found drops of liquid that smelled of formic acid on the feathers of steppe pipits that had been actively anting to rid themselves of mites. The pungency of all substitute substances that birds sometimes smear on their plumage when ants are unavailable leaves little doubt that their purpose is to deter parasites. Among those listed by Lovie Whitaker and other researchers are toxin-oozing millipedes; grasshoppers, which regurgitate a noxious brown liquid; wasps; raw onion; lime fruits; burning matches or tobacco; prepared mustard; vinegar; and mothballs.

A. H. Chisolm vividly described anting by a flock of starlings in Australia:

Each bird snatched up an ant from a gravel path and dabbed it quickly first under one wing and then under the other, after which the insect usually was dropped ... All the actions of the Starlings were very rapid. Two birds in particular nearly fell over backward while rearing up smartly and applying ants beneath their tails. I saw no evidence of the insects being eaten. When the birds departed, the path was bespattered with dead and maimed ants, some 50 percent of which had their abdomens burst, while the others were more or less intact. The species was ... a type that bites and sprays quickly, which possibly helps to explain the rapidity of the Starlings' actions.

"Some birds, according to K. E. L. Simmons, of the Department of Psychology of the University of Bristol in England, are more sophisticated and use ants with considerable finesse. The Pekin robin holds an ant by its thorax, leaving free the abdomen, which contains the formic acid glands and the mechanism that sprays the acid. Depending upon from which side of the bill the abdomen protrudes, the bird turns its head and applies the ant to the appropriate wing. At first it uses the ant as a 'bug bomb,' holding the struggling creature so that it sprays formic acid onto the undersurface of the flight feathers. But eventually the ant dies. Then the bird daubs the fluids that ooze from the ant's crushed body onto its feathers."



Gilbert Waldbauer


What Good Are Bugs?: Insects in the Web of Life


Harvard University Press


Copyright 2003 by the President and Fellows of Harvard College


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