Comfort Behavior in Birds

As spring migration picks up the pace, all of us are excited about the return of Maine’s migratory breeding birds. Particularly during migration, birders eagerly try to see as many species as possible in a morning. It’s great fun to find that wayward Kentucky Warbler or Blue Grosbeak. However, I suggest that a closer, leisurely look at even the most common birds can be rewarding.

Like other animals, birds need to keep their skin clean and healthy. Feather maintenance is a priority as well. Most of these body-care behaviors are said to be stereotyped; that is, the birds do these same behaviors in the same way all of the time.

One of the most widely recognized stereotyped behaviors birds use to keep clean is bathing. A bird typically takes a bath by first immersing and then suddenly raising the head and then rapidly beating the wings. This bathing behavior is inborn. Young Northern Goshawks on the bare ground are induced to try to bathe when they see a brood-mate splashing in water.

In arid environments, birds take dust baths rather than water baths. It is thought that the dust removes some of the oils from the bird’s skin, which would otherwise cause matting of the feathers.

Usually, birds engage in preening after taking a bath. Preening involves the application of waxy oils to the feathers to preserve feather moisture and flexibility, waterproof the feathers and clean the feathers. The waxy oils are produced by the preen gland or uropygial gland, located on the rump at the base of the tail.

To preen, a bird rubs its bill against its preen gland to pick up some secretions from the preen gland and then uses its bill to apply the waxy oils to all the feathers of its body.

The preen glands of some birds also produce secretions that protect the feathers from feather-digesting bacteria and fungi. Other secretions may deter feather lice. In a group of birds called the hoopoes, the preen gland produces a foul-smelling substance that deters mammal predators. Hoopoes are the skunks of the bird world!

Birds spend a considerable amount of time preening. Many birds will preen their feathers once an hour. While preening, the wing and tail feathers are drawn through the bill to restore their shape. Feather parasites may be removed by preening as well.

Herons and egrets produce a peculiar type of feather called powder down. The powder down feathers are never molted but rather grow continuously. The claw of the middle toe of each foot has a comb-like undersurface that is used to crush the tips of the powder down feathers. The talcum-like powder down is spread over the feathers with the comb-claw. The powder down apparently has the same function as oil from the preen gland. The preen glands of herons are vestigial (like a human appendix) and therefore herons do not oil their feathers.

A less known form of feather and skin maintenance in songbirds is called anting in which a bird treats its feathers with ants or some other substitute material. Many ants give off pungent chemicals when they are disturbed. These chemicals serve to kill feather lice and other skin and feather parasites.

Some birds that engage in anting behavior do so passively. For instance, American Crows will spread its wings and sit down on an ant colony. The angry ants crawl through the crow’s feathers, reducing the number of parasites.

In active anting, a birds picks up one or more ants in its bill and then actively jabs them among its feathers. The bird usually ants more vigorously on the underside of its body, particularly under the wings and tail. Sometimes, an anting bird eats the ants after anting; at other times, the ants are released. Birds that practice active anting behavior include the orioles, jays and starlings.

Some songbirds don’t rely on ants for anting. Beetles, bugs, wasps, raw onion, vinegar, cigarette butts, walnut juice, lime fruit, orange peeling and mothballs may be picked up for use in anting.

Anting in Common Grackles has been observed a number of times with ants and substitute materials, including mothballs. Group anting by grackles has been described in Ohio. A woman had put out a large number of mothballs in her flower gardens to keep rabbits out. Grackles discovered the mothballs and began using them to ant. Up to two dozen grackles were seen anting at once!

Anting has been reported widely in the songbirds. Over 250 species from over 40 families have been reported to ant.

[This column originally published on May 5, 2007]