Forest songbird abundance and viability at multiple scales on the Monongahela National Forest, West Virginia.

摘要

Songbird-habitat relationships were investigated using three interrelated studies, each at multiple scales, on the Monongahela National Forest, West Virginia. In each study I used landscape (25 km2), transect (2500 m), and point (50-m radius point count plot) scales.;In the first study, I investigated bird abundance and species richness at these scales in four major forest types: mixed mesophytic, northern hardwoods, red spruce, and dry oaks. At the landscape scale, forest types differed in bird abundance (p = 0.07) and species richness (p = 0.08). Abundance of forest-interior species, Neotropical migrants, and nine key indicator species were greatest in the mixed mesophytic (p 0.05). Bird abundance and species richness differences at the transect scale were significant (p 0.001) and were related to differences in stand height and canopy structure. Relatively little variation in bird abundance or richness occurred between points within a transect, even though transects were oriented to capture the maximum variation in elevation. Environmental variables explained much more variation at the transect than at the local scale.;The second study compared bird abundance (through point counts) and viability (through nest search survival data) across mixed mesophytic landscapes ranging from 42% to 81% forest core area. Nest search plots were long and narrow (200 m by 2000 m), and superimposed over point count transects. Forested core area and edge density showed little relationship to bird abundance or viability at landscape or transect/plot scales. A distinct edge effect was found up to 25 m from edges; at greater distances the relationship of nest survival to distance from edge was ambiguous. Nest survival was greater at edges of regenerating clearcuts than along roads, possibly because of greater concealment.;In the third study I compared bird abundance and species richness in upland versus riparian zones. Riparian zones were areas within 50 m of first- and second-order mountain streams. Overall, more birds were found on upland than on riparian sites; this was true at landscape, transect, and point scales. Abundance of Acadian flycatchers, Louisiana waterthrushes, wood thrushes, and hooded warblers was greater along streams, however.;Results of these studies suggest that this national forest is providing abundant habitat for Neotropical migrants and interior species. Of the four forest types, mixed mesophytic was generally associated with the greatest numbers of Neotropical migrants and interior species. Forest fragmentation effects were evident only at the local scale, and distinct only within 25 m of edges. With the exception of a few species, bird abundance and species richness in the riparian zones investigated were little different from those on upland sites.