Bald Eagle Migration
Not all eagles migrate; those that do have complex migratory patterns. While migrating, eagles ride columns of rising air called thermals and can average speeds of 30 mph (50 kilometers). Effortlessly, an eagle can circle in a strong thermal to a high altitude, and then glide long distances in the direction of its migration until it finds the next column of rising air. Generally, eagles follow seasonal food supplies; as lakes and streams freeze over, bald eagles must go south to find open fresh water or head to the coast.
Adult bald eagles, such as this one, do not migrate with juveniles. Newly fledged eagles migrate before their parents; no one knows how young birds know when and where to travel.
Some fledgling eagles wander in a wide range their first few years. Some return to their origin, while others do not. Only the young eagle knows if this is a conscious decision or if it simply loses its way.
Adult bald eagles begin fall migration when the northern lakes and rivers freeze over. Depending on location, they usually migrate to the coast or large rivers near dams, where the water remains open. Wind currents play a large role in determining their flight pattern.
Many eagles in Florida do not migrate, but remain year-round. Most bald eagles migrate south in the fall to areas with sufficient food, and return north in the spring to nest. In the spring, eagles migrate quickly; during the fall they migrate rather slow, sometimes remaining in an area for a week or so before continuing on.
Eagle with a tracking device.
Navigation - Migrating birds acquire directional information from landscape features and wind direction which can be influenced by major land forms, scents, the stars and sun as well as Earth's magnetic field (increasing evidence indicates that birds collect magnetic field information through specialized eye receptors).
Migrating eagles fly during the day at speeds averaging 30 miles per hour. To help them soar, eagles use thermals, which are rising currents of warm air and up-drafts generated by terrain, such as valley edges or mountain slopes. Soaring is accomplished with very little wing-flapping, enabling them to conserve energy. Long-distance migration flights are accomplished by climbing high in a thermal, then gliding downward to catch the next thermal, where the process is repeated.
Bald eagles tend to migrate in groups. A "stream" of migrating bald eagles can be twenty to thirty miles long, with birds spread out about a half mile apart.