Effects of forest harvesting on Bufflehead and Common Loon foraging behavior

抄録

We compared foraging behavior of Bufflehead (Bucephala albeola Linnaeus) and Common Loon (Gavia immer Brünnich) on eight lakes in harvested and unharvested boreal mixedwood forest in northern Alberta, Canada. For one summer before (1996) and two summers after (1997, 1998) forest harvesting around three of the eight lakes, we recorded the duration of Bufflehead and Common Loon dives. After logging, forested buffer strips 100 m-wide separated cut-blocks from lakes (‘harvested lakes’). ‘Unharvested lakes’ were surrounded by ≥450 m of undisturbed forest throughout the study. There were no detectable differences in dive duration between harvested and unharvested lakes for Bufflehead or Common Loon. Correlations between environmental variables (water clarity, fish biomass, depth) and the duration of Common Loon dives were not significant. However, the duration of Bufflehead dives differed between lakes, unrelated to forest harvesting. The duration of Bufflehead dives was negatively correlated with water clarity but was not significantly correlated with fish biomass. While our study shows that the foraging behavior of Buffleheads was affected by lake conditions, the utility of aquatic birds as indicators of the effects of forestry on western boreal lakes remains unproven.