Shorebird Use and Mortality at a Large Canadian Prairie Lake Impacted by Botulism

We surveyed the shoreline of a large terminal lake in southern Saskatchewan (Old Wives Lake) for sick or dead birds and estimated shorebird numbers during avian botulism outbreaks. Nearly double the number of shorebirds were present in 1999 compared with 1998. The most commonly observed shorebirds in both years were the Short-billed Dowitcher (Limnodromus griseus) and Long-billed Dowitcher (L. scolopaceus). Water levels were monitored, revealing a greater drawdown effect in 1998. Small species (e.g. Least Sandpiper (Calidris minutilla), Semipalmated Sandpiper (C. pusilla), and Sanderling (C. alba)) were much more common in 1998. Much of the data that exist on shorebird mortality during botulism kills is in the form of unpublished annual agency clean-up reports. These reports suggest that the American Avocet (Recurvirostra americana), yellowlegs (Tringa melanoleuca and T. flavipes), and the small Calidris sandpipers are the most commonly affected species. We suggest some biases inherent in these c...