Riparian and upland breeding-bird assemblages along headwater streams in Michigan\u27s Upper Peninsula

Comparative studies of riparian and upland bird communities have focused primarily on larger streams (greater than second order). We examined breeding-bird assemblages in relation to their proximity to small head-water streams in northern hardwood forests of the Otter River watershed in Michigan\u27s Upper Peninsula, USA. At 10 study sites, we used fixed-radius point counts to survey bird assemblages and measure forest habitat characteristics along riparian and upland transects. Forest structure and composition differed between riparian and upland areas, with more conifer stems and higher conifer basal area on riparian transects. We detected 46 bird species during 1999 and 2000. During each year, total bird abundance was similar for riparian and upland areas, whereas bird species richness and evenness was higher in riparian areas. When we pooled bird species by foraging guild, we found that foliage-gleaning birds were more abundant in riparian areas. We found 12 bird species exclusively in riparian areas and only 2 species exclusively in the uplands. The northern parula (Parula americana) and Black-burnian warbler (Dendroica fusca) were among 5 species more abundant on riparian transects, whereas the least flycatcher (Empidonax minimus) and red-eyed vireo (Vireo olivaceus) were among 5 species more abundant on upland transects. Although the vegetative gradient between riparian and upland habitat was subtle along these first- and second-order streams, breeding-bird assemblages differed between riparian and upland forests. This suggests that individual bird species respond to vegetative features of even narrow riparian areas. Managers working in northern and mixed-hardwood forests therefore should consider maintaining habitat diversity in the form of native conifers, even on the smallest first-order streams