Ducks generally possess two different plumages, a basic (eclipse) plumage and an alternate (breeding) plumage. For males, these can be quite different. Alternate plumage serves to clearly identify the bird as a member of its species and to attract a mate. Therefore, we see the colorful plumages of males during winter and spring. However, once the job of finding and maintaining a mate is done, males soon find a suitable habitat to replace the wing feathers. During wing molt, ducks cannot fly and are extremely vulnerable to predation. Hence, the males also replace the colorful body feathers with drab basic (eclipse) plumage, enabling them to hide more easily while they cannot escape trouble by flying. There is more than meets the eye with feathers. They are complex structures that perform a variety of important functions. Indeed, feathers are one portion of the anatomy to which birds (and people) give particular attention, and one of many avian features that elicit our awe and appreciation.
Because of crafty experiments performed in planetariums, scientists know that some birds actually use the stellar map. Presented with the normal night sky in a planetarium, a caged spring migrant bird will orient itself to the north. If you switch the orientation on the planetarium so that the North Star is actually south, the bird moves toward the south instead of moving in the direction of true north as it should.
Landmarks may be important for navigation, not as compasses, but as directional cues. If asked how to get to Ducks Unlimited's national headquarters in Memphis, I would say: "Turn right at Starbucks and make a left at that good Mexican restaurant." If you ask my husband, he would tell you: "Go west on Wolf River Road and head south on One Waterfowl Way."
Using landmarks to give directions makes sense to me and is probably common among nighttime migrants, which respond to major topographic features, such as coastlines, mountain ridges, and major waterways such as the Mississippi River. One of the nonvisual cues that is believed to aid bird navigation is the earth's magnetic field. Now don't try this at home, but when magnets were placed on the heads of captive birds, they did not fly in the correct direction even on sunny days.
One investigator noted a change in direction and altitude of migrating birds when a powerful underground antenna was turned on, interfering with the earth's magnetic field. Even more interesting than a bird's ability to navigate is its ability to "home." Homing is the ability to find home when a bird is released in an unfamiliar place or from an unfamiliar direction. How waterfowl actually do this is not at all clear.
They likely imprint information about their home breeding and wintering areas and use navigational cues to return to them. Ducks and geese differ in their rates of homing. Adult female ducks often return to former breeding sites. As many at 75 percent of adult female canvasbacks return to their breeding area each year, often nesting in the same pothole where they nested the previous year.
This is also true of cavity-nesting species such as wood ducks, buffleheads, and goldeneyes. Blue-winged teal, on the other hand, have one of the lowest homing rates of all ducks: From 5 to 15 percent return to their former home.
Geese are different because they pair for life. In geese, because pair bonds are long lasting, both males and females home to the same breeding area.
Family units including the mother, father, and goslings will stay together for up to a year. They go to the same wintering area and return the next year to the same breeding area as a family. The young goslings likely learn their migration routes and breeding and wintering areas from their parents.
In young, new pairs, the male will follow the female to her birthplace. If re-pairing does occur, the male goose will follow the female to her breeding area.
The ability to navigate over many miles from breeding to wintering grounds is an amazing adaptation. It is likely that most birds use a combination of visual and nonvisual cues, as well as homing. Navigation and migration behavior is very difficult to study and therefore has not been fully resolved, but we quest for answers with great enthusiasm every fall when the birds return to the same wintering ground, or every spring when I see the same female wood duck nesting in her old box from the year before.
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