Waterfowl Feathers

By David Brakhage

When you are out hunting or watching ducks, the coloration of the birds' feathers is one of the first things you notice. Each species has its own distinctive plumage, which is invaluable when trying to identify birds in the field. A drake pintail's long twin tail feathers, white underparts, and soft brown topside can be easily distinguished from a male wood duck's squared-off tail feathers and multicolored plumage.

Feathers are indeed among the defining characteristics of waterfowl and other birds. Birds, in fact, are the only animals that have feathers. And while feathers have many specialized functions, their most important jobs are to protect birds from the elements and to enable flight. In bitter cold, wintry conditions feathers are a duck's first line of defense.

Waterfowl have three types of feathers: contour, flight, and down. Contour feathers collectively serve as a protective outer shell. Each feather is composed of a central shaft with a continuous series of paired vanes that line up on opposite sides of the shaft. Tightly interlocking barbules line the edge of each vane and hold them together like Velcro. They overlap one another much like shingles on a roof, forming an almost impenetrable barrier to wind and moisture. Feathers are also held in place by specialized muscles just under the skin. Using these muscles waterfowl can fluff up their feathers and move them back into position at will.

Located on a bird's wings and tail, flight feathers are a variation of contour feathers that are designed to withstand the stress and strain of flight. Because they must support a bird's weight in flight, they are connected directly to ligaments or bone for greater structural integrity. Unlike body feathers, flight feathers have vanes of unequal width and are always narrower on their leading edge. This characteristic, which is especially obvious in primary flight feathers, helps provide lift and forward propulsion in flight.

Down feathers serve as an inner layer of insulation that traps warm air against a bird's body. They have a short shaft and no interlocking barbules, giving them a light, fluffy appearance. Before the advent of modern synthetic insulation, duck and goose down was widely used by people to line blankets, clothing, and sleeping bags. Even today, the warmth-to-weight ratio of eider down is still unsurpassed when dry.

Interestingly, smaller birds often have more feathers than do larger ones. Swans are a notable exception because of their long necks, which are covered with a large number of small feathers. Roughly 80 percent of the feathers on a tundra swan are found on the bird's head and neck.

Female waterfowl also use down to line their nests and keep their eggs warm. During the egg-laying process, hens pull more and more down from their body, creating a bare patch on their abdomen. This "brood patch" allows females to more efficiently transfer heat from their bodies to the eggs. When hens leave the nest for brief periods during incubation, they pull a layer of down over their eggs with their bills to protect them and keep them warm while they are away.

Feathers are a marvel of natural engineering, but they require constant care and must be replaced periodically to maintain peak performance. Waterfowl spend a couple hours each day just caring for their feathers. An oil gland at the base of the tail secretes a preening fluid that keeps feathers soft and pliable, which in turn prevents them from breaking, keeps them waterproof, and enhances their aerodynamics. Waterfowl use their bills to distribute this fluid throughout their feathers while preening. Ducks and geese also use their bills to realign their feathers and reconnect any Velcro-like barbules that have become separated.

But even with regular preening and other care, feathers break and wear out. Any feather that is pulled out or lost completely is replaced right away; broken and worn feathers aren't replaced until the birds molt. Molting, the natural process in which birds routinely replace some or all of their feathers, varies in timing and frequency among waterfowl species. All ducks and geese undergo a simultaneous wing molt, when flight feathers are replaced. During this period waterfowl are completely flightlessusually for a month or sountil new flight feathers grow in.

Ducks replace their contour feathers at least twice a year. During winter and spring many male ducks have gaudy breeding plumage, which serves to attract prospective mates. Shortly after the breeding season, however, males undergo a body molt, replacing their showy "alternate" plumage with drab "basic" or "eclipse" plumage. These henlike feathers help conceal drakes while they are flightless during the wing molt. But as soon as drakes can fly again in late summer, they begin a second molt and gradually develop their breeding plumage as fall progresses.

Female ducks molt as well, but differences between their basic and alternate plumage are far more subtle. Hens molt into their basic plumage just before nesting and keep this plumage until after the wing molt and brood-rearing activities are complete. Geese typically undergo just one complete molt a year, which has a much less noticeable effect on the birds' appearance.

Everyone who enjoys viewing ducks appreciates their colorful and in many cases iridescent plumage. Hunters have the privilege of examining these remarkable feathers in hand. The next time you bag a duck or goose, take a few minutes to explore the bird's many different kinds of feathers and their colors and patterns. You'll once again be reminded of the wonders of nature.

Chemical coloration is produced by pigments that either absorb or reflect wavelengths of light. White feathers, for example, have little or no pigment, so all wavelengths are reflected. In contrast, black feathers contain the dark pigment melanin, which absorbs light.

Iridescence is a structural phenomenon associated with the barbules on feather vanes. Iridescent feathers have numerous, overlapping barbules that reflect and absorb light in varying amounts. The result is a lustrous shine that changes color depending on the intensity of the sun and the angle at which the feathers are observed.