Resident Nongame Waterbird Use Following Biomanipulation of a Shallow Lake

Abstract

Abstract: We examined the use of Lake Christina, Minnesota, USA, by nongame waterbirds following an autumn 2003 application of rotenone to eliminate its fish base and enhance migrating canvasback (Aythya valisineria) habitat. The only nongame waterbirds observed attempting to nest in 2004 were black terns (Chlidonias niger), but they failed to hatch any young. We recorded 246 Western grebes (Aechmophorus occidentalis) on Lake Christina in the spring of 2004, but by mid‐June most had left the lake. During this period, few fish were available, and we suggest that although the emergent vegetation was suitable for nesting, the lack of food prevented colony formation. In spring 2005, small fish were again available on the lake, and numbers of all nongame species were greater than in 2004. We located 315 western grebe nests, of which 198 hatched ≥1 young (63% of all attempts). Landscape‐level manipulation may enhance habitat for some species but also has the potential to exclude trophic levels from future use and should be considered when manipulating large‐scale systems.