Brrr-irds: Adaptations help feathered friends

Some Americans dread winter and will travel to warmer parts of the country to wait it out.

Others enjoy the cold and can’t wait for the first snow. Most just adapt, adding layers or staying indoors in front of a warm fire.

Birds face the winter similarly.

Many birds, about 340 species, do leave North America to winter in Mexico, Central America, South America and the Caribbean. But plenty remain year round.

Look outside on a blustery winter day and you’ll still see songbirds flitting at feeders and ducks swimming in icy creeks. Nearly one million waterfowl fly to the Chesapeake region from northern breeding grounds. Winters here suit them just fine.

Birds, like mammals, are warm-blooded, meaning they must maintain a constant body temperature as the temperature around them changes. To do this, they spend much of their time feeding so they can generate enough heat.

Meat-eating birds, like hawks and owls, may stay put if prey is available.

Birds that can switch from a primarily insect diet to a seed diet can stay put throughout the winter.

To survive severe weather, birds have developed adaptations.

One feature that sets birds apart from other animals is feathers. Birds’ bodies are covered with an outer layer of fairly stiff but flexible contour feathers and an under layer of fluffy down feathers. The contour feathers provide protection against wind, rain and snow. The down feathers act as a layer of insulation.

Tightly knit together and overlapping, feathers protect the skin and hold a layer of air over the bird’s body. Because birds control the position of their feathers through muscular movements, they are able to “puff” themselves up.

Many birds have an oil gland located at the base of their tail. Secreted oil is rubbed over the feathers with the beak or bill. This preening creates a shield that helps block wind and repel water. Ducks, geese and swans can survive in water that is close to freezing because the amount of oil in their feathers makes them waterproof.

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Office in Annapolis.

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