Richness Permanent resident birds reach their greatest species richness in portions of California and Texas, states with avifaunas that are relatively unique for North America. The fewest numbers of species occur across Canada and the northern Great Plains south through the Rocky Mountains and Great Basin. Population Trends Positive trends prevail on the Great Plains from Oklahoma northward into southern Canada, and then across the Great Lakes region to New England.
Similar trends predominate in California and portions of Arizona.
Negative trends are apparent from New Mexico and Texas across the southern states to the Carolinas, and along the Appalachian Mountains to Ohio. Negative trends also occur along the central Rocky Mountains and adjacent Great Plains northward into Montana, and locally in the Great Basin from Nevada and Utah into Oregon. This percentage is similar to the woodland bird group, which is not surprising since many permanent residents occupy woodland habitats. However, the geographic patterns of positive and negative trends are markedly different from those of the woodland bird group.