June 24, 2008

Study: Birds Are Migrating Earlier

U.S. scientists say many birds are migrating earlier because of global warming, but some might not be able to keep pace with changing climate.

Researchers at Boston University and the Manomet Center for Conservation Sciences analyzed changes in the timing of spring migrations of 32 species of birds along the coast of eastern Massachusetts since 1970. Their findings show eight of 32 bird species are passing by Cape Cod significantly earlier on their annual trek north than they were 38 years ago.

The scientists believe the reason for the earlier migration is global warning, since temperatures in eastern Massachusetts have risen by 2.7 degrees Fahrenheit since 1970.

Species that winter in the southern United States are generally keeping pace with warming temperatures and earlier leafing of trees. But birds wintering farther away in South America are not changing migration times despite the rising temperatures in New England.

The scientists conclude such long-distance migrants will probably experience environments increasingly different from the ones for which they are adapted, resulting in a mistiming with their insect food supply. That might be causing some of the recently documented declines among songbird populations.

The study appears in the journal Global Change Biology.