Of the more than 5 billion individual birds that migrate south for the winter, it’s estimated that about half (mostly young birds from the previous breeding season) do not make it back to their breeding range in spring.
While the benefits of migration are substantial, migratory species pay a price for them. Likewise, migratory raptors can prey on spring’s bounty of rodents, fruit- and nectar-feeding birds find fresh meals, and fish-eating seabirds and plant-eating waterfowl also benefit by traveling to where the getting is good. Thus, insect-eating birds benefit from an incredible seasonal abundance of food. In Arctic regions, for example, huge numbers of insects take advantage of warmth and long sunny days to fulfill their own breeding and feeding needs. By migrating farther north, however, birds can exploit a new crop of insects and nectar-laden flowers. Why, then, don’t migrants stay put in springtime? Because staying means competing for a limited supply of nest sites and food during the breeding season, when birds need a plentiful supply of protein-rich food to feed their young. By migrating to tropical regions, however, they can tap into resident birds’ year-round supply of food.
Nor can a nectar-feeder, such as a hummingbird, rely on flowers. Insect-eating land birds, for example, can’t depend on a steady supply of insects during a northern winter. Birds that migrate do so because it’s proven to be an effective strategy for survival and reproduction. On any day, birds are migrating somewhere, but spring and fall are the busiest seasons-a time when billions of birds wing their way through the skies, day and night. This Whimbrel is stopping to feed as it makes its way from its winter home in the Caribbean to the Arctic tundra, where it will breed and raise its young with its lifelong mate. Place: A tidal marsh near the coast of North Carolina.Ī large bird probes in the mud with its downward-curving bill, searching out worms, crustaceans, and mollusks.
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