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Birds Migrate Earlier, But Some May Be Left Behind As Climate Warms Rapidly (June 22, 2008) — Many birds are arriving earlier each spring as temperatures warm along the East Coast of the United States. However, the farther those birds journey, the less likely they are to keep pace with the ...
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www.sciencedaily.com/releases/2007/03/070302082310.htm
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In North America, the ratio of migratory to nonmigratory birds varies greatly from region to region. In high arctic regions (northern Alaska, northern Canada, and Greenland), where many shorebirds and water fowl nest, the entire population often consists of migratory birds who are only ... On to Why Birds Migrate Page 2...
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www.paulnoll.com/Oregon/Birds/migrate-why.html
www.paulnoll.com/Oregon/Birds/migrate-why.html
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Why do birds migrate?; The reasons are complex and not fully understood. But a simple explanation is food and a safe place to breed. Birds which breed in the summer in the extreme north such as the Arctic benefit from an abundance of food as plants and insect life flourish in the long daylight hours;
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www.naturia.per.sg/buloh/birds/migration.htm
www.naturia.per.sg/buloh/birds/migration.htm
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They migrate because of climate change, food or when they are ready to breed
http://wiki.answers.com/Q/Why_do_birds_migrate
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Bird Migration 2, When do birds migrate and How do they know where they are going ... Speed - birds often fly faster when on a migratory flight then they do during ordinary flight. Thus distances of 200 to 400 miles a day are commonplace among long distance migrants. Some birds, however, migrate more slowly, e.g.
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www.earthlife.net/birds/migration2.html
www.earthlife.net/birds/migration2.html
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Tucson AZ (SPX) Mar 07, 2007 - Why do some birds fly thousands of miles back and forth between breeding and non-breeding areas every year whereas others never travel at all? One textbook explanation suggests either eating fruit or living in non-forested environments were the precursors needed to evolve migratory behavior.
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www.terradaily.com/reports/Why_Do_Birds_Migrate_999.htm...
www.terradaily.com/reports/Why_Do_Birds_Migrate_999.html
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Not so, report a pair of ecologists from The University of Arizona in Tucson. The pressure to migrate comes from seasonal food scarcity. ... "If you are faced with food scarcity, you have two options," Boyle said. "You can either forage with other birds or you can migrate."
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www.eurekalert.org/pub_releases/2007-03/uoa-wdb030107.p...
www.eurekalert.org/pub_releases/2007-03/uoa-wdb030107.php
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Why birds migrate we can only conjecture. Without doubt the growing scarcity of food in autumn is the controlling factor with many of them; and this would seem to be an excellent reason for leaving the region of their summer sojourn. ... Some North American birds migrate southward only a few hundred miles to pass the winter,
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www.oldandsold.com/birds/bird-study-19.shtml
www.oldandsold.com/birds/bird-study-19.shtml
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Birds migrate because food in their habitat is scarce, not because of a picky diet. ... It's food scarcity, not dietary preferences, that motivates birds to migrate thousands of miles back and forth between breeding and non-breeding areas each year, new research shows.
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www.livescience.com/animals/070302_hungry_birds.html
www.livescience.com/animals/070302_hungry_birds.html
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