Predatory Warblers and the Control of Spruce Budworm in Conifer Canopies

Abstract

Asked where the greatest diversity of bird life is, most people would say the tropical forests, and they would be correct. Tiny Costa Rica, for example—less than a fourth the size of Minnesota—has more than fifty species of hummingbirds alone. Traveling northward, the diversity of bird life thins, until we reach the North Woods, which has the greatest number of breeding bird species anywhere north of Mexico, on average sixty to sixty-seven species per 5-mile survey route according to the Breeding Bird Survey. The family Parulidae, the warblers, is a major part of this diversity. According to my Peterson Field Guide, there are forty species of warblers in eastern North America; fully twenty-nine of these breed in the North Woods, three quarters of all the warbler species of eastern North America.

The North Woods support twenty-nine species of warblers, the highest diversity of a group of related birds north of Central America. By foraging in different parts of a spruce or fir canopy, some of these warblers can partly control spruce budworm populations.