Migration Mysteries

Our wintering songbirds will soon depart for parts north; one morning, we’ll wake up and they’ll be gone, having flown hundreds of miles through the night while we slept. It’s not until relatively recently that we’ve begun to understand the mysteries of migration. In the 17th century, one outlandish theory that held currency was that the birds flew to the moon for the winter. Aristotle thought that swallows spent the winter buried in mud.

I recently spoke with Rebecca Heisman — author of the new book Flight Paths, about bird migration and the scientists who figured out some of what really goes on — who will be in town on April 19 for a free talk sponsored by the Santa Barbara Audubon Society and the Santa Barbara Public Library.

Just how do nocturnal migrants navigate? Heisman: Birds actually have a number of different ways to navigate, so that if one isn’t feasible on a certain day, they can use other ones. There were really cool experiments done decades ago, where they put birds under planetariums [and] projected the night sky, which could be rotated in different ways. They showed that birds can orient themselves using the stars in the night sky. They can orient themselves using the position of the sun as well, using sunrise and sunset. Some birds have been shown to be able to use the appearance of landmarks on the ground below. And then birds can also sense their magnetic field: They have sort of an internal compass where they can sense magnetic north, so they have a lot of different ways that they can use to figure out where they’re going.