The reason for bird migration is easy to understand: Take mobile animals and a seasonally fluctuating food supply, and the natural consequence is migration. Long ago and to this day, the birds that moved — or move in the right direction — survive.
Birds that migrate at night, such as indigo buntings, are able to navigate by the stars. Day migrants get compass directions from the sun and use landmarks such as the Mississippi River. Night migrants include some larger birds, such as the secretive rails and the American woodcock, and most small insect-eating birds. Think wrens, most thrushes, kinglets, vireos, warblers, tanagers, orioles and most sparrows.
Hawks, eagles, vultures, cranes and pelicans migrate by day. Also, crows, jays, most blackbirds and the eastern bluebird migrate join them. Small birds with strong flight — swifts, swallows and hummingbirds — are day-migrators usually migrate by day, although swifts and hummingbirds can migrate also at night.
Loons, grebes, ducks, geese, shorebirds, nighthawks, herons, and the eastern kingbird migrate by day and night. The American robin and many gulls move at all hours.
Of the 240 species of birds that nest in Minnesota, only about 24 are wholly nonmigratory. Some include several species of grouse and owls, four species of woodpeckers (downy, hairy, red-bellied and pileated), the white-breasted nuthatch, northern cardinal, house sparrow and ring-necked pheasant.
Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.
