Did you know? (Bird migration facts)

Billions of birds seasonally undertake the perilous journey of migration.

It is difficult to visualize a Swainson's Hawk, weighing only about two pounds, migrating from its breeding site on the Saskatchewan prairies to wintering ground in southern Argentina.

Equally amazing is a semipalmated sandpiper, weighing only an ounce, migrating from the Canadian Tundra to northern South America.

It is hard to believe a Ruby Throated Hummingbird, weighing only 1/6 ounce, flying from its nesting area in New Hampshire to wintering grounds in Costa Rica.

Migration is not just the seasonal movement of birds during spring and fall to avoid harsh weather. This is just part of the story.

Migration evolved as a way for animals to exploit resources that are seasonally abundant and to avoid times or places where life sustaining resources are scarce.

Many species can tolerate cold temperatures if food remains plentiful. However, if it is not available, the birds must migrate. The availability of food is the driving force in the evolution of migration patterns.

To fly long distances a bird must carry plenty of fuel. Fat is the currency of migration because it provides the greatest amount of energy per unit of weight. The more fat a bird has the farther it can fly. Fat is indispensable. Without it, a migrant cannot fly or survive long periods of inclement weather.

Birds are extremely sensitive to weather and atmospheric patterns. They purposefully select times and altitudes with the best wind directions and the best wind speeds.

The majority of birds migrate at night. However, hawks make their seasonal moves during day time hunting in the late afternoons.

More birds are active during migration at night due to internal clocks, ecology, endocrinology, neurobiology, physiology and evolution according to researchers. Actually, very little is known about the intricacies of migration.

Migratory flight is a result of an infinite number of decisions. To complete it successfully, birds must make many decisions and all must be correct ones. Such decisions include: what time of day or night to fly; what speed to travel; how high to fly; which direction to fly; and where to land.

Migration continues to intrigue scientists, and they continue to study the subject finding out more each year.

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