The boreal forest stretches across the Northern Hemisphere in Canada, Asia, and Europe. Scientists compared the bird communities in Europe, Siberia, western Canada, and eastern Canada.
Although the bird species were quite different at the different study sites, the bird communities were all dominated by small songbirds that gleaned insects from the leaves. Most of the birds are migratory, taking advantage of a flush of insects in the breeding season and avoiding the harsh, snowy winters by migrating to warmer, southern regions.
In the European sites the chaffinch (Fringilla coelebs) is by far the most common bird and dominates the bird community. The other sites were dominated by a variety of warblers. It is unclear why the chaffinch is so successful in Europe, but deforestation may be a factor. It is one of the few forest birds to winter in agricultural areas.
This article summarizes the information in this scientific paper:
Greenberg, Russell S. 1999. Warblers, finches, and tits: the structure of boreal forest foliage-gleaning guild. The Condor, 101: 299-310.
Teachers, Standards of Learning, as they apply to these articles, are available for each state.