Abstracts

Presented by Luke Fara - Email: lfara@usgs.gov

Previous studies suggest that long-tailed duck (LTDU; Clangula hyemalis) populations are in decline and further efforts have been made to better understand their population distributions. Long-tailed ducks rank high in priority with the Sea Duck Joint Venture and have been a focal species in large-scale wintering telemetry projects in eastern North America. However, LTDUs radiomarked on the Atlantic coast and Lake Ontario have shown very little use of Lake Michigan, where recent aerial surveys indicate a large overwintering population. To address information needs on the spatiotemporal patterns of migration, breeding ground affiliations, winter site fidelity, and habitat use of LTDUs wintering on Lake Michigan, we radiomarked 25 LTDUs and followed their movements. Of the 25 radiomarked LTDUs, 13 survived >60 days and provided information on habitat use and migration. Long-tailed ducks used relatively shallow waters closer to shore during daylight hours (average across all birds 22.3 m and 5.4 km, respectively) but moved to deeper waters well offshore at night (average across all birds 61.0 m and 11.9 km, respectively) while using the open water of Lake Michigan. Most LTDUs moved southward on Lake Michigan as winter progressed and then relocated to Green Bay and the northern third of Lake Michigan before spring departure. James Bay and Hudson Bay served as primary stopover sites during spring and fall migration, and the territory of Nunavut, Canada was used during the breeding season. Spring departure of radiomarked LTDUs from Lake Michigan occurred in mid-May and fall arrival occurred in late October and early November. Movement information will aid managers dealing with key conservation issues, such as delineating and managing the eastern population of LTDUs, site planning for future offshore wind energy development on Lake Michigan, and evaluation of food web links associated with avian botulism type E on the Great Lakes.