Any reproduction or re-use is strictly prohibited without the express written permission of the Executive Director of the Sanctuary. Bill Hilton Jr. Feathers, not flight, are the distinguishing characteristic of birds. In addition to providing a rigid airfoil for flight, feathers insulate a bird from summer heat and winter cold. Along with body oils, feathers help waterproof birds, and shield their skin from dust and debris. The various colors of feathers may serve to hide or advertise a bird's presence.
Larger species tend to have more feathers than smaller species.
Outside the tropics, birds tend to lose some of their feathers over the course of each breeding season, replacing them only in fall-just in time for winter. The number of feathers varies little among members of the same species. Although almost all raptors are born with a relatively thin coating of down feathers, most develop a second thicker coat of down within days of hatching. By the time they are ready to fledge, young birds have acquired most of their first year's plumage. In most raptors, feathers cover all but small portions of the faces, feet, and toes of adult birds, but there are exceptions.