Study of Bird Migration
A flock of Barnacle Geese during autumn migration
Example of long distance bird migration routes.
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat, or weather.
Sometimes, journeys are not termed
"true migration" because they are irregular (nomadism, invasions, irruptions) or in only one direction
(dispersal, movement of young away from natal area). Migration is marked by its annual seasonality. [1]
In contrast, birds that are non-migratory are said to be resident or sedentary.
Approximately 1800 of the world's
10,000 bird species are long-distance migrants. [ citation needed]
General patterns
Flocks of birds assembling before migration southwards (probably
Sturnus vulgaris)
Migrating waders in Roebuck Bay,
Western Australia
Many bird populations migrate long distances along a flyway . The most common pattern involves flying north in the spring to breed in the temperate or
Arctic summer and returning in the autumn to wintering grounds in warmer regions to the south. Of course, in the
Southern Hemisphere the directions are reversed, but there is less land area in the far South to support long-distance migration. The primary motivation for migration appears to be food; for example, some hummingbirds choose not to migrate if fed through the winter. Also, the longer days of the northern summer provide extended time for breeding birds to feed their young. This helps diurnal birds to produce larger clutches than related non-migratory species that remain in the tropics. As the days shorten in autumn, the birds return to warmer regions where the available food supply varies little with the season.
These advantages offset the high stress, physical exertion costs, and other risks of the migration such as predation.
Predation can be heightened during migration: the Eleonora's Falcon , which breeds on
Example of long distance bird migration routes.
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat, or weather.
Sometimes, journeys are not termed
"true migration" because they are irregular (nomadism, invasions, irruptions) or in only one direction
(dispersal, movement of young away from natal area). Migration is marked by its annual seasonality. [1]
In contrast, birds that are non-migratory are said to be resident or sedentary.
Approximately 1800 of the world's
10,000 bird species are long-distance migrants. [ citation needed]
General patterns
Flocks of birds assembling before migration southwards (probably
Sturnus vulgaris)
Migrating waders in Roebuck Bay,
Western Australia
Many bird populations migrate long distances along a flyway . The most common pattern involves flying north in the spring to breed in the temperate or
Arctic summer and returning in the autumn to wintering grounds in warmer regions to the south. Of course, in the
Southern Hemisphere the directions are reversed, but there is less land area in the far South to support long-distance migration. The primary motivation for migration appears to be food; for example, some hummingbirds choose not to migrate if fed through the winter. Also, the longer days of the northern summer provide extended time for breeding birds to feed their young. This helps diurnal birds to produce larger clutches than related non-migratory species that remain in the tropics. As the days shorten in autumn, the birds return to warmer regions where the available food supply varies little with the season.
These advantages offset the high stress, physical exertion costs, and other risks of the migration such as predation.
Predation can be heightened during migration: the Eleonora's Falcon , which breeds on