Northern Prairie Wildlife Research Center
Forest and Rangeland Birds of the United States
Natural History and Habitat Use
Distribution of Birds in the United States
There are several broad patterns in the ecological distribution of breeding birds
in the United States. There is a generally increasing continuum of breeding bird
species from the drier areas of the Southwest and West to the more moist forests
of the Northeast (Peterson 1975). Regions dominated by desert vegetation have
relatively simple avifaunas that contain a few prominent species. Regions with
complex mixed forests contain many rather evenly distributed species, although
much regional variation occurs along this gradient. In the Great Plains, the number
of species increases from Texas to the Canadian border (Cook 1969, Peterson 1975).
This latitudinal increase may reflect patterns of glaciation or a more heterogeneous
landscape on the northern plains, but in general the avian community in grasslands
is organized by the most obvious structural feature, grass height (Cody 1968).
Mountainous regions of the United States have relatively diverse avifaunas,
largely because their considerable topographic relief compresses several different
vegetation zones into a relatively small area, rendering them ecologically diverse
(Cook 1969). Closely related habitats, or habitats with similar physical profiles
or complexities, exhibit similar bird diversities (Peterson 1975).
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