By Tina Yerkes, Ph.D.
Duck and goose migrations raise as many questions as there are answers Another beautiful weekend has arrived, and we set off on a canoe trip to a river that we have never visited. The conversation in our car is predictable and goes something like is: To my husband I say, "Do you have the map and the directions?"
His reply: "Kind of." My retort: "What do you mean 'kind of'? You don't have directions, do you?" "I know where I'm going" is his reply. I quietly hold my tongue because in an hour I know we will be lost and he will refuse to stop at a gas station and ask for directions.
If we cannot find our way across the state without a map, how do birds navigate such long distances from their wintering grounds to their breeding areas and back again to the wintering grounds? How do some return to the exact same place where they had a nest the previous year, or to the exact same wintering ground? Are ducks and geese different in their navigation behavior?
Birds use several visual and nonvisual orientation mechanisms to navigate. Some of the visual cues include the sun, polarized light, the stars, and even landmarks. How many of us wear polarized sunglasses when we fish? Do you realize that birds can use the axes of polarized light to determine the position of the sun and perform sun compass orientation? Birds that navigate at night obviously cannot use polarized light, but the stars can provide a good road map for nighttime migrants, and many waterfowl species do utilize star orientation for navigation.