Historical and Current Distribution and Populations of Bird Species in Prairie-Oak Habitats in the Pacific Northwest

Abstract

The loss and degradation of prairie-oak habitats has resulted in significant changes in bird species breeding distributions and populations. Among the 49 species highly associated with prairie-oak habitats, 21 have experienced extirpations, range contractions, and/or regional population declines. Three species have been regionally extirpated as breeding species since the 1940s, including Lewis's woodpecker, which historically occurred throughout the region. Eleven species have experienced local or ecoregional extirpations and/or range contractions. The predominant pattern of range contraction starts at the northern edge of a species range and moves southward. Nine species have relatively small regional populations, six with limited distribution in the Klamath Mountains ecoregion, and three with small and patchily distributed breeding populations throughout the region. There are nine species with significantly declining regional population trends with a high degree of confidence based on Breeding Bird Survey data, and five with similar declines using Christmas Bird Count data. Several other species may be declining based on a lower degree of confidence in the data or anecdotal observations. These include both endemic subspecies, streaked horned lark and Oregon vesper sparrow, which have regional population estimates of <2,000 and <3,000 birds, respectively. Six species have expanded their range in prairie-oak habitats in the last 50 years. The predominant pattern of range expansion starts at the northern edge of a species range and moves northward. Recommended actions to support prairie-oak bird conservation include range-wide and local inventories and monitoring to determine status, and evaluations and implementation of reintroductions or federal listings as appropriate.