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DEVELOPMENT OF A BIRD INTEGRITY INDEX: MEASURING AVIAN RESPONSE TO DISTURBANCE IN THE BLUE MOUNTAINS OF OREGON, USA
Citation:
BRYCE, S. A. DEVELOPMENT OF A BIRD INTEGRITY INDEX: MEASURING AVIAN RESPONSE TO DISTURBANCE IN THE BLUE MOUNTAINS OF OREGON, USA. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 38(3):470-486, (2006).
Impact/Purpose:
To use bird assemblage information to assess human impacts to 28 stream reaches in the Blue Mountains of eastern Oregon
Description:
The Bird Integrity Index (BII) presented here uses bird assemblage information to assess human impacts to 28 stream reaches in the Blue Mountains of eastern Oregon. Eighty-one candidate metrics were extracted from bird survey data for testing. The metrics represented aspects of bird taxonomic richness, tolerance or intolerance to human disturbance, dietary preferences, foraging techniques, and nesting strategies that were expected to be positively or negatively affected by human activities in the region. To evaluate the responsiveness of each metric, it was plotted against an index of reach and watershed disturbance that included attributes of land use/land cover, road density, riparian cover, mining impacts, and percent area in clearcut and partial cut logging. Ten of the 81 candidate bird metrics remained after eliminating unresponsive and highly correlated metrics. Individual metric scores ranged from 0 to 10, and bird integrity index scores varied between 0 to 100. BII scores varied from 88.6 for a minimally disturbed, reference stream reach to 30.4 for the most highly disturbed stream reach. The BII responded clearly to varying riparian conditions, and it was sensitive to the cumulative effects of disturbances, such as logging, grazing, and mining, that are common in the mountains of eastern Oregon. Finally, this eastern Oregon BII was compared to an earlier BII developed for the agricultural and urban disturbance regime of the Willamette Valley in western Oregon. The BII was successfully adapted to a different ecological region by modifying metrics to fit hypothesized avian responses to characteristic eastern Oregon stressors. The eastern Oregon BII distinguished differences in condition among stream riparian zones under a human disturbance regime dominated by natural resource activities, where a site¿s departure from regional reference condition was not as sharp or irreversible as it was in the agricultural/urban conditions of western Oregon.