Most migratory songbirds are attracted to forests of the north due to the availability of soft, easy-to-eat caterpillars. The blue-headed vireo has the added adaptations of a short bill and strong muscles for munching beetles with hard outer shells. This increases the bird’s prey options—especially when nestfuls of young birds need to be fed.
The blue-headed vireo prefers to breed in areas with conifers such as hemlock. Because the vireo arrives in breeding areas early in the spring, most other trees have not yet produced leaves for camouflage and protection. The vireo uses hemlocks for courtship and the first nests of the season, moving into other trees as leaves begin to appear.
Because of this dependence on hemlock, the blue-headed vireo’s population may eventually be affected by the spread of an invasive insect, the hemlock wooly adelgid. This pest is rapidly spreading throughout the northeast, damaging and killing the hemlock trees on which vireos depend. Ecological data collected by research stations such as Powdermill is helping scientists monitor the impact on the blue-headed vireo and other species in the face of threats such as the adelgid invasion.