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BIRD GUILDS AS INDICATORS OF ECOLOGICAL CONDITION IN THE CENTRAL APPALACHIANS
Citation:
O'Connell, T. J., L E. Jackson, AND R. P. Brooks. BIRD GUILDS AS INDICATORS OF ECOLOGICAL CONDITION IN THE CENTRAL APPALACHIANS. ECOLOGICAL APPLICATIONS 10(6):1706-1721, (2000).
Description:
As part of the U.S. Environmental Protection Agencys (EPAs) Environmental Monitoring and Assessment Program (EMAP), we developed an indicator of biotic integrity based on songbird community composition. Because songbirds occur in a wide variety of habitat types, the bird community index (BCI) is intended to integrate ecological conditions across a large physiographic region exhibiting diverse land-cover attributes and intensities of human use. Comprised of multiple biological metrics, our indicator is an index that ranks bird communities according to the proportional representation of 16 behavioral and physiological response guilds. Relative proportions of "specialist" and "generalist" guilds, viewed as indicators of structural, functional, and compositional ecosystem elements, determine condition. We developed the BCI from 34 reference sites in central Pennsylvania that represent a gradient of ecosystem condition from near pristine to severely degraded. Upon satisfactory demonstration that the BCI could discriminate between categories of ecosystem condition, we applied the BCI to independent samples of 126 sites across the Mid-Atlantic Highlands Assessment (MAHA) area. Sites were selected using EMAP?s probability-based sampling design, and therefore represent the total land area in the region. To verify the BCIs discriminatory properties, we compared the BCI assessment to independent gradients of landscape disturbance applied to both the 34 reference sites and the 126 MAHA sites. The BCI identified four categories of biotic integrity in the MAHA area. Our assessment indicated that 16% of the area is in excellent condition, 27% is good, 36% is fair, and 21% is in poor condition. Urban and agricultural sites differ in their respective guild compositions, but are not separable by overall BCI score. Forested sites supporting the two highest-integrity categories contain different site-level vegetation attributes, but cannot be separated by landscape-level land-cover composition. This research also defined thresholds of land-cover change where significant shifts in BCI categories were observed.