How do Birds Migrate?

For centuries people have marveled as some birds mysteriously disappear each fall. As late as the 16th century people thought birds hibernated! Rather than ending the mystery, the discovery of migration has prompted even more questions.

Why do birds migrate? Many bird species travel north in spring to take advantage of the longer days and abundant food sources, both of which aid in raising young.  Cold weather in the fall reduces food sources, requiring birds to move where food is plentiful.

Many factors help birds migrate. Genetics may explain the direction, timing and distance of migration for some species. But others, like geese and cranes, learn migration routes through social contacts with family and other flock members.

Birds use landmarks like rivers, mountains and forests to orient themselves over familiar territory. The sun acts as a daytime compass, and birds are able to compensate for its movement to keep a straight course. On overcast days, at night, or over featureless oceans, birds use the stars and the earth’s magnetic field to guide them.

Many birds have heightened senses that may assist in navigating. Some birds have magnetic material in their bills which allow the birds to sense the Earth’s magnetic field like a compass needle. The eyes of other species are very sensitive to polarized light which aligns with the magnetic field. Seabirds have heightened senses of smell and memory for those odors which help them find their way across the oceans.

Bird migration is a complex truly amazing phenomenon which continues to excite and puzzle backyard bird watchers and ornithologists alike!