Wednesday, October 03, 2007

How Do Birds Migrate Such Long Distances?

The two main reasons birds migrate are for food and for a safe place to breed.There are several factors that go along with making such a dangerous trip. Its been shown that in some birds, changes in day length cause glands in the birds'bodies to produce hormones that produce changes birds’ physiology. These physiological changes prepare them for migration.
The migrating birds need to use as many things to their advantage to save energy for flying as much as possible. Birds utilize the winds to their favor. They do this so they can go long distances and burn minimal energy. Flying such long distances is an extreme energy cost to the bird but they use the environment to their advantage. They may shift altitude to find the best wind "conveyor belt". Winds at high altitude may blow in the opposite direction from wind on the ground, and usually areblowing strongly. Migrating birds usually fly at about 500-2000 meters above the ground. Larger birds, such as Canadian geese, rely on hot air rising from the ground in the mornings to gain altitude by simply soaring. These birds usually migrate during the day. They may also follow strong updrafts along ridges.

Besides depending on fat reserves for energy, migrating birds also need to eat alot to fuel their regular feather molts. Their feathers must be in tip-topcondition for their long migration trips both to the south for the winter, and back to the north in the summer. Different species molt at different times; but most molt just after breeding and before the migration to warmer areas.
Studies suggest birds orientate themselves to the compass points using the position of the sun during the day, and the stars at night. They can also sense magnetic north. They also use other clues such the way the land is laid out. They use their sense of smell, and focus on the scent of the sea and the sound of the waves on the shores. They also depend on the winds through mountain passes.

The most interesting fact about migrating birds is that it is an innate behavior, and they automatically know where to go, along using environmental cues to help them along the way. There are several species of migrating birds that abandon their young as soon as they fledge (grow their flight feathers). Later the young make the trip to the south on their own without any help from the parents.

Posted by Marielle Livesey (2)


At 5:37 AM, Anonymous SAF said...

Interesting blog, it is amazing how birds are born with an ability to sense magnetism.


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