Carolyn McClelland, age 13, of Austin, Tex., for her question:

DO BIRDS MOLT?

Some animals molt. Molting is the process in which worn out hair, skin or feathers is shed by an animal. Birds shed their feathers once a year. Some kinds of birds even shed their feathers three times each year.

Each complete molt in birds takes from four to six weeks.

Birds have a very systematic way of molting. The feathers fall out, one after another, in a regular order. As they fall out, they are replaced in a correspondingly regular order with new feathers.

Because the molting is regularly spaced in some birds, they are able to fly during molting periods. When a bird has two molting seasons, the first is to replace bedraggled winter plumage and the second is to deck the bird out for the mating season.

The process of molting varies with different animals. Many mammals shed their hair once a year, usually in spring. Scaly reptiles, such as snakes and lizards, and shellfish, such as lobsters and crabs, also undergo molts. They replace their outer coverings with new ones.