One or Michigan's most important IBAs is the Detroit River and its adjacent open water IBAs: Lake St. Clair, and western Lake Erie basin. Up to 10% of the world's Canvasbacks have been counted within this ecosystem during fall migration and early winter, and thousands of other diving ducks, Tundra Swans, and American Coots use this area as a migration stopover each year. It is usually very difficult to photograph these huge associations, but Jerry Jourdan has produced a fine panoramic here:
In spending just 60 seconds estimating the number of individuals in the photo by groups of 100 I estimate there are at least 4,500 individuals present in this photo. This is very good practice for obtaining numerical estimates of large flocks of birds. I also recommend this very helpful counting utility and eBird's estimation tips. And as always, be sure to report your counts of all species to eBird, where the information will instantly become available to the IBA program and all conservation agencies, with the click of one button.