Bird migration takes place two times a year. Generally it happens in the spring and autumn of the year in the temperate regions. In the tropics, movement happens during the dry and rainy seasons.
Food is a driving force. Birds migrate in temperate regions to places with better sources of food. In the tropical regions the reason is to move to areas with less or more water.
The birds that live in the northern parts of the United States over the winter live mainly on seeds, tree buds and dry berries. Live flying insects are scarce in northern regions in winter. So, most flying insect-eating birds migrate.
The majority of those insect-eaters that remain north in winter are small birds that live mainly on insect eggs and the developing young of insects.These birds include chickadees, nuthatches, titmouse and woodpeckers.
Where Do They Go?
The great majority of birds migrate in a generally north-south direction. Most birds that bred in Canada and the northern United States fly south for the winter. Many migrate as far south as South America. The seasons south of the equator are opposite those in North America. Therefore, North American birds that migrate to southern South America arrive in time for that region’s summer. And plenty of insects.
Bird migration can take place day or night.Some species migrate by day. Others fly at night. Bird migration usually starts at dawn or dusk. Birds can travel alone or in flocks, depending on species.
How Do They Migrate?
We don’t completely know how birds navigate. But, scientists have experimented and made several suggestions. Birds may use several compass techniques to find their way.
- an internal compass that tells which way is north, south, east, west, etc.
- birds posses magnetite in their beaks which measures the strength of the earth’s magnetic field
- the sun as a directional aid
- the star patterns as a compass
- polarized light compass – using the patterns of polarized skylight at dawn and dusk
These methods and others we may not know about help birds to find their way. Many birds use flyways or routes to migrate from one area to another.
No South American birds migrate to North America. They fly only as far north as the tropics, spend the winter there and then return south for the summer.
Most waterfowl, such as ducks and geese only migrate short distances. The generally nest and overwinter on the same continent.
Shorebirds tend to migrate in flocks and usually at night.