Bird communities of northern forests: Patterns of diversity and abundance

Abstract

Diurnal bird communities in Southeast Alaska and adjacent Canada, censused in 1992-1994, sometimes had higher diversity and abundance in deciduous than coniferous forest. However, variation within each broad vegetation type and among years obscured any general pattern. Furthermore, rarefaction curves did not differ between forest types and a wider comparison between the communities of deciduous and coniferous forests in western North America was variable in both magnitude and direction. Thus, there is little evidence for a general trend toward greater diversity in bird communities of western and northern deciduous forests. Both deciduous and coniferous forests of the far north are geologically young, and there was some evidence that deciduous forest, at least, may not be saturated with bird species. Certain species were missing or shifted from conifer habitat elsewhere to deciduous habitat in our area. Coastal islands with coniferous forest and mainland patches of deciduous habitat supported about as many species as expected from the number of individuals present. A small number of bird species dominated the community at each site, but the dominant species differed considerably among locations. Proportional similarity of coastal and interior forest was low, except for locations at the north end of the Inside Passage, which supported species characteristic of both coastal and interior forests. The similarity of community composition in deciduous and coniferous stands was also low, especially on the coast.