Distribution, abundance, and habitat association of riparian-obligate and -associated birds in the Oregon Coast Range

We studied the abundance, distribution, and habitat associations of the aqu atic-foraging riparian-associated vertebrate community along four stream ba sins transecting managed forests in the Oregon Coast Range, 1992-1994. The riparian-associated community we observed consisted primarily of birds with few observations of mammals. Belted kingfishers (Ceryle alcyon), American dippers (Cinclus mexicanus), great blue herons (Ardea herodias), and mallar ds (Anas platyrhynchos) comprised >85% of these observations, but we observ ed only one group (greater than or equal to 1 individual observed together) from this community for each kilometer of stream surveyed. Bird abundances among years were not different tall P > 0.05). Species distribution was af fected by stream order, stream basin, and season in each species, but to va rying degrees. Belted kingfishers, common mergansers (Mergus merganser), gr eat blue herons, green herons (Butorides striatus), and mallards were more abundant in larger, 6(th)-order streams than in smaller, 4(th)-order stream s (P < 0.05). Dippers used step channel units disproportionally more and ri ffles disproportionately less than expected (P < 0.5). Similarly, kingfishe rs used fewer rimes and more pool channel units than was expected (P < 0.5) . Key habitat components that were predictive of use were species specific. Most notably, the presence of a forested riparian area, streamside trees, and valley walls that constrain the stream were important predictors of use by the three most abundant species; dippers, kingfishers, and great blue h erons. Monitoring programs to assess populations of these species in mounta inous habitat must be sensitive to the potential effects of stream order, b asin, and season and encompass a large spatial and temporal extent.