Relationship of riparian reserve zone width to bird density and diversity in southeastern British Columbia

Abstract

British Columbia forestry guidelines require riparian management areas of 20 to 50 m width between small streams and cutblocks, composed of reserve zones (no timber harvest) and/or management zones (limited timber harvest). Guidelines in Kootenai National Forest, Montana, limit forest harvesting for 30 m adjacent to permanent streams. As one step in providing a basis to assess such guidelines, we compared (1) habitat structure between spruce-dominated riparian forest and pine-dominated upland forest, (2) breeding bird characteristics (density of detections, species richness, species diversity and species equitability) between riparian and upland forest, and (3) breeding bird characteristics between riparian reserve zones of various widths (averaging 70, 37, or 14 m wide). The study occurred in the Montane Spruce biogeoclimatic zone of southeastern British Columbia. In relation to upland forest, riparian forest had greater tall shrub and canopy cover, but fewer live trees. Snag density, low shrub cover, and coarse woody debris did not differ at P lt 0.05. The two habitat types did not differ in mean bird species richness per site, but riparian forest had greater species diversity and species equitability, greater density of all species combined, and greater density of three individual species. The density of all birds combined, all riparian-associated birds combined, and three of the four riparian-associated species increased with increasing reserve zone width. Species diversity and species equitability did not differ significantly among treatments. The widths of riparian management areas required under current British Columbia and Kootenai National Forest guidelines are considerably narrower than the widest category of reserves investigated in this study (70 m). Our data indicate that prescribed riparian management areas under current guidelines will have lower densities of total birds and of riparian-associated birds than if reserves were required to average 70 m in widthKinley and Newhouse "Relationship of riparian reserve zone width to bird density and diversity in southeastern British Columbia." Northwest Science. 1997; 71(2): 75-8