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SITE CHARACTERIZATION USING BIRD SPECIES COMPOSITION IN EASTERN OREGON, USA
Citation:
Ernst, T. L. AND S. A. Bryce. SITE CHARACTERIZATION USING BIRD SPECIES COMPOSITION IN EASTERN OREGON, USA. Presented at Wildlife Society, Burlington, VT, September 6-10, 2003.
Description:
We conducted riparian bird surveys at 25 randomly selected stream reaches in the John Day River Basin of eastern Oregon as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP). At each reach along a kilometer-length transect, we conducted 10 minute bird assemblages to assess the ecological condition of the basin. Here we present the initial step in condition assessment using bird species composition, which is to partition the data into relatively homogeneous units based on bird species assemblages. We examined the distinction and association of 91 bird species by applying a combination of cluster analysis, nonmetric multidimensional scaling (NMS), and multiple response permutation procedure procedure (MRPP). The analyses categorized the sample sites into three distinct bird assemblages (a shrubland assemblage and two forestland assemblages). Using Mantel's test, NMS, discriminant analysis and classification tree analyses, we assessed the relationships between the three groups and associated environmental variables. The shrubland bird assemblages occurred at elevations below 1000 m; they were composed of bird species associated with shrubs such as sagebrush, mockorange, and white alder, and a mix of deciduous and evergreen trees, such as water birch and juniper. The mid- and high-elevation forest bird assemblages occurred at elevations above 1000 m and were composed of species associated with ponderosa pine and spruce-fir forest. The high elevation (spruce-fir) forest bird assemblage experienced higher precipitation than the mid-elevation forest assemblage, a higher riparian canopy density, and, structurally, a higher percentage of the reach with three vegetation layers. These exploratory analyses confirm our intuitive field knowledge about the ecoregional distribution of bird assemblages and provide more detailed information about the elevational preferences of particular bird species.