Bird migration

Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds. Many species of birds migrate. Migration carries high costs in predation and mortality, including from hunting by humans, and is driven primarily by availability of food. It occurs mainly in the northern hemisphere, where birds are funneled on to specific routes by natural barriers such as the Mediterranean Sea or the Caribbean Sea.

Types of Migration

Bird migration is not a simple phenomenon and can be classified into different types based on distance, season, or the birds' behavior:

• Long-distance migration: Birds that breed in the northern parts of the world and migrate to warmer southern climates.
• Short-distance migration: Birds that move only over short distances, from higher to lower altitudes or from one region to another.
• Partial migration: When only a portion of a population migrates, while the rest remain at the breeding site.
• Irruptive migration: Unpredictable movements which occur in some years but not others, often in response to food availability.

Mechanisms and Control

Birds navigate during migration using a variety of methods. They can use the sun during the day, the stars at night, and the earth's magnetic field at any time. Some species also use olfactory cues and landmarks. The exact mechanisms of how birds navigate and control their migration patterns are complex and involve a combination of genetic predisposition, learning, and environmental factors.

Evolution of Bird Migration

The evolution of bird migration is believed to be closely linked to bird ecology and life histories. Changes in climate and habitat availability over millions of years have likely shaped the migratory habits of bird species, selecting for traits that maximize reproductive success and survival.

Conservation Issues

Bird migration faces numerous threats from human activities. Habitat destruction, climate change, hunting, and collisions with man-made structures pose significant risks to migratory birds. Conservation efforts are crucial to protect migratory routes and stopover sites that are vital for the survival of these species.

See Also

• Bird conservation
• Flyway
• Ornithology