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After effects flock of birds download4/13/2024 The seasonal abundance of insect food and greater day length allowed them to raise more young (4–6 on average) than their stay-at-home tropical relatives (2–3 on average). Why make such an arduous trip north in spring? One idea is that through many generations the tropical ancestors of these birds dispersed from their tropical breeding sites northward. They also incorporate responses to weather, geography, food sources, day length, and other factors.įor birds that winter in the tropics, it seems strange to imagine leaving home and embarking on a migration north. They’ve evolved over thousands of years and are controlled at least partially by the genetic makeup of the birds. While short-distance migration probably developed from a fairly simple need for food, the origins of long-distant migration patterns are much more complex. The pattern of migration can vary within each category, but is most variable in short and medium distance migrants. Despite the arduous journeys involved, long-distance migration is a feature of some 350 species of North American birds. Long-distance migrants typically move from breeding ranges in the United States and Canada to wintering grounds in Central and South America.Medium-distance migrants cover distances that span a few hundred miles.Short-distance migrants make relatively small movements, as from higher to lower elevations on a mountainside.They are able to find adequate supplies of food year-round. One way to look at migration is to consider the distances traveled. The term migration describes periodic, large-scale movements of populations of animals. As winter approaches and the availability of insects and other food drops, the birds move south again. Escaping the cold is a motivating factor but many species, including hummingbirds, can withstand freezing temperatures as long as an adequate supply of food is available. Here’s more about how migration evolved.īirds that nest in the Northern Hemisphere tend to migrate northward in the spring to take advantage of burgeoning insect populations, budding plants and an abundance of nesting locations. The two primary resources being sought are food and nesting locations. Why do birds migrate?īirds migrate to move from areas of low or decreasing resources to areas of high or increasing resources. Of the more than 650 species of North American breeding birds, more than half are migratory. But geese are far from our only migratory birds. Geese winging their way south in wrinkled V-shaped flocks is perhaps the classic picture of migration-the annual, large-scale movement of birds between their breeding (summer) homes and their nonbreeding (winter) grounds.
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