Bird Migration Basics

Bird migration for hummingbirds begins when the autumn months arrive. The hummingbirds head south on their yearly winter bird migration. Bird migration is the mass movement of birds between widely separated areas they occupy at different seasons. In North America, migration is traveled to and from the northern breeding grounds and southern wintering grounds, yet there are birds that move past areas where there is plenty of food and through climates they could easily survive in.

Why Do Birds Migrate?
Birds instinctively know when, where and how to travel during their migrations. Man has not discovered the reasons or the methods of the migration of birds though.

An anonymous treatise was published in London in 1730, which claimed the theory that birds went to the moon every winter. Another theory was that small birds were carried across the ocean on the backs of larger birds. One theory stated that birds hibernated like bears. Aristotle held the theory of transmutation, which suggested that birds changed into other species as the seasons changed.

Some ornithologists believe that birds began migration patterns because of the ice age. Some claim all bird species originated in the tropics and moved northward, hunting better food supplies and then moved south again to escape harsh winters.

When Do Birds Migrate?
Some birds migrate only by day like ducks, geese, swifts, swallows, herons and hawks. They are strong birds and people note their passage. Daylight movement is called diurnal migration.

Nocturnal migration is the movement of weaker flyers or shy and secretive species during the night. They feed in the day and move at night. Thrashers, thrushes, vireos, warblers, creepers, cuckoos, wrens, rails, bitterns, tanagers and sparrows make up this group.

Where Do Birds Go?
Altitudinal migration refers to movement of mountain dwelling species, such as pipits, chickadees, juncos or siskins. These are birds that, rather than taking long flights south, fly to valleys and lower altitudes and lowlands to wait out the winter.

Some species are permanent residents of their area. Bobwhite, ruffled grouse and house sparrows are a few examples of the birds that remain in their native area throughout the year.

Transient visitants are birds that just visit on their way to another region. They do not nest or settle for a season in the area, but may be sighted there. Birders refer to birds that come and go for breeding, nesting and wintering as summer residents, summer visitants or winter visitants, as the case may be.

How Fast and Far Do Birds Fly?
The majority of birds fly 20 to 40 miles per hour, depending on weather conditions. Ducks and geese generally fly in the 40 to 55 miles per hour range. Herons are slow flyers at less than 20 miles per hour. Ducks, hawks, swifts and a few other birds can fly much faster.

Most birds take a casual approach to migration, flying a few hours to eight hours during a stretch. Most don't travel every day. Some take only days to move hundreds of miles, while others spend weeks on the same distance. Mallards and Lesser Yellowlegs have been clocked at over 300 miles per day, while a Lincoln's sparrow averaged about 50 miles in a day's time.