Fall Migration - Annual Life Cycle

How Ducks Migrate

Birds migrate long distances from wintering grounds to breeding areas and back again to the wintering grounds with visual and nonvisual cues. Visual orientation mechanisms that ducks use include the sun, polarized light, stars, and even landmarks. Birds use the axes of polarized light to determine the position of the sun and perform sun compass orientation. Navigation at night requires migrants to use stars to orient their direction. Crafty experiments performed in planetariums have shown scientists that some birds actually use a stellar map to find their way around in the night. Landmarks may be important for navigation, not as compasses, but as directional cues. Coastlines, mountain ridges and waterways such as the Mississippi River are major topographic features that may be considered landmarks.

One nonvisual cue that aids in navigation is the Earth's magnetic field. When the Earth's magnetic field is obstructed migrating birds often change or alternate direction and altitude. Homing, another nonvisual cue, is a bird's ability to find its way home when released in an unfamiliar place or direction. 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 therefore has not been full resolved.