Primary Investigator:
Rob Baden, M.Sc. Candidate
Supervisors:
Dr. Scott Petrie, Long Point Waterfowl Executive Director
Dr. Jack Millar, University of Western Ontario
Dr. Michael Schummer, Long Point Waterfowl Scientist
The lower Great Lakes have historically been an important staging and wintering area for waterfowl. Recently, increasing numbers of diving and sea-ducks have wintered on the lower Great Lakes, including Lake St. Clair and the Detroit and St. Clair Rivers. Waterfowl that over-winter in northern climates encounter weather conditions that may limit access to food resources.
Rob is investigating the tradeoffs associated with wintering at northern latitudes in two diving ducks, Canvasbacks and Redheads, by analyzing changes in each species’ lipid and protein reserves, diet, Rob measures a Canvasback prior and foraging behaviours throughout winter. Canvasbacks (n = 148) to dissection and Redheads (n = 66) were collected from Lake St. Clair and the Detroit and St. Clair Rivers from 8 November 2008 to 7 March 2009; birds from a 2008 winter die-off were also included in the study.
Initial results showed that mean body mass, lipid, and protein levels of Canvasbacks and Redheads were well above values recorded for each species collected during the 2008 winter die-off. Few of the birds collected during 2008/09 had lipid levels less than 10% of their body weight. Increases in body mass and lipid levels during February and early March, prior to spring migration, suggest that food availability was not limiting during the winter of 2008/2009.
Diets of these two diving duck species did not vary much throughout winter. Canvasbacks primarily consumed tubers of wild celery, whereas Redheads consumed muskgrass and the stems and leaves of various pondweed species. Both species foraged almost exclusively in shallow, open water habitats on Lake St. Clair during the fall and early winter, and moved to open, fast water areas of the St. Clair and Detroit Rivers as the lake froze in January. Zebra mussels occurred in a small percentage of the collected birds’ diets and were likely ingested accidentally.
January temperatures during 2008 were warmer than the long term average, and resulted in a larger number of birds remaining in the Lake St. Clair region until temperatures plummeted in late January and early February. The increased foraging pressure on food resources by staging birds in January, and the below average temperatures in February are likely factors that contributed to the starved birds found during the winter of 2007/2008. January temperatures during 2009 were colder than normal, but moderated above long term averages in February and March. Overall, Canvasbacks and Redheads fared well during the winter of 2008/2009 in the Lake St. Clair region. Access to food resources, limited mainly by ice, appears to be the main obstacle for these over- wintering duck species.