Jim Gilbert's Journal
September 17, 1999
Fall Bird Migration
Much has been written about the reasons birds migrate. The bottom line is that because of seasonally fluctuating food supply and birds being mobile animals, the natural consequence is migration. The birds that move in the right direction survive. Night-migrating birds such as the indigo bunting are able to navigate by the stars. Night migrants include some larger birds, such as the secretive rails and the American woodcock, and most small insect-eating birds, such as wrens, most thrushes, kinglets, vireos, wood warblers, tanagers, orioles and most sparrows. Many of the small night migrants, while feeding by day, also move slowly during daylight hours.
Day migrants get compass directions from the sun and use landmarks such as the Mississippi River. Hawks, eagles, vultures, cranes and pelicans migrate by day. Also, crows, jays, most blackbirds and the eastern bluebird migrate by day. Small birds of strong flight, such as swifts, swallows and hummingbirds usually migrate by day, although swifts and hummingbirds can migrate at night.
Loons, grebes, ducks, geese, shorebirds, nighthawks, herons, the eastern kingbird, American robin and many gulls can be both day and night migrants.