Riding the Edge of Winter
From Oak Harbor, Ohio, Kenn writes: In fall, most birds migrate south before they would have to. Most migratory birds in North America leave their northern nesting grounds and start southward long before the weather begins to turn bad, long before the food supply begins to dwindle. The birds apparently are keyed to changes in the length of the day, not to local conditions, so they fly away from their summer homes while resources are still abundant. But there are exceptions. Not surprisingly, one of the exceptions is the surprising Sandhill Crane. Cranes are different from most birds in the nature of their migration anyway: their routes are learned, not instinctive. A baby Indigo Bunting, to cite an example of a typical migrant, is born with an instinct to migrate to Central America in fall without any help. A baby Sandhill Crane is born with an instinct to follow its parents in the fall. Cranes learn their routes and their stopover sites and their wintering sites, and they can change ...