Three Weeks for a New Feather Coat

An African penguin steps out of the ocean onto a rocky beach in southern Africa. Water rolls off its feather coat. Although this bird does not live on Antarctic ice, the ocean where it feeds can be cold. Its feathers solve an important problem: they help keep cold water away from its skin and slow the loss of body heat.

Small Feathers, Big Job A penguin's coat looks smooth from a distance, but it contains many small feathers packed closely together. Their outer parts overlap like shingles on a roof. This arrangement helps water slide over the surface instead of soaking through. Near the skin, soft, fluffy feather parts hold a layer of air. That trapped air provides insulation, slowing the movement of heat from the warm body to the colder surroundings.

In a close-up diagram of this coat, arrows can point to the outer tips and the fluffy parts below. The caption, "Two jobs in one coat," describes how the feathers resist water outside and trap insulating air underneath.

Daily Feather Care The coat needs regular care. A penguin uses its bill to straighten and clean its feathers, a behavior called preening. It also spreads oil from a gland near the base of its tail. The oil helps keep the feathers in good condition. Careful preening keeps the feather surface working as a close-fitting barrier, rather than a coat full of gaps.

Time for a New Coat Even with care, feathers wear out. About once a year, an adult African penguin goes through a molt, replacing its worn feathers. It replaces nearly its whole coat during one short period, rather than changing a few feathers at a time over many months. New feathers grow beneath the old ones, pushing them out. The penguin may look puffy and untidy during this change.

During its molt, the penguin stays on land for about three weeks. Its changing coat cannot protect it well enough for feeding trips in the ocean. Before the molt begins, the bird eats extra food and stores fat. It uses that stored energy while it waits ashore without eating.

Once the new coat is ready, the penguin can return to the water to find food. Staying ashore may seem like a pause in its busy life, but it is essential. The coat's overlapping feathers, trapped air, daily care, and yearly replacement work together to help this ocean swimmer stay warm and dry.