For instance, many species of migratory birds are insect eaters. During the cold winters of the United States and Canada, when insects are scarce, migrants that have flown south thrive in areas with warmer temperatures and abundant bugs, like the tropics of Mexico and Central and South America. In the spring and summer months, when days are warmer and longer in North America, these same birds return to take advantage of the rich abundance of insects that help fuel their breeding and rearing of young. A migratory corridor is simply a series of areas that provide food, shelter, and water for the migratory birds, whose tremendous physical exertions demand frequent refueling. Unlike some other species, birds do not require continuous migratory corridors.
Birds can stop overnight in a pond in a suburb or city, as well as a wetland, rice field, or lake.
Still, migratory journeys are most successful when migratory corridors remain as intact and undisturbed as possible. As human populations grow, and as we move into and change wild areas, these migratory corridors, and their important resources, are becoming less and less continuous. The breaking up of migratory corridors makes a bird's long journey even more difficult. Although some birds have adapted to be able to use areas that have been changed by human activity, the best resources remain in wild areas. Careful conservation planning is necessary to help preserve the right kind of natural areas in just the right places in order to keep migratory corridors connected.