By Richard M. Kaminski, Ph.D.
Dr. Frank C. Bellrose, renowned scholar of waterfowl migration, wrote in his classic book, Ducks, Geese and Swans of North America, “Most of the 775 species of birds in North America migrate, but because waterfowl are highly visible in migration, they epitomize this phenomenon to most people. And to most hunters, waterfowl migration is an eagerly awaited event because of the drama they witness from a blind and the satisfaction it brings to them.”
My passion for waterfowl “hatched” near my hometown, Manitowoc, Wisconsin, on Lake Michigan, where I witnessed countless migrating ducks, geese, and swans from beach and boat blinds. As Mary Hopkins sang, “Those were the days, my friend. We thought they’d never end.”
Indeed, those days of spectacular skeins of migrating waterfowl have not ended, though some redistributions of the birds have occurred along the flyways. Breeding waterfowl populations have been up and down, generally every other decade since I began waterfowling in the 1950s with Pa’s pump gun and paper reloads. These population dynamics are normal. Waterfowl populations rebound with improved habitat conditions as most North American waterfowl species have proven to us repeatedly, and most recently during the 1990s. So long as changing seasons and waterfowl habitats exist along the flyways, waterfowl migrations also will persist. However, waterfowl abundance and their habitats will not be constant; we should expect changes in both time and space.
Although some facets of waterfowl migration remain puzzling, research has fused certain pieces of the puzzle. Because we are currently experiencing or anxiously awaiting fall migration, I’ll summarize some of our knowledge on why, when, and where waterfowl migrate during fall in North America.
Why do waterfowl migrate? According to Dr. Bellrose, “the biological reason for migration is survival.” Additionally, survival is a prerequisite for reproduction. These two life-history components are all that matter to waterfowl and all wildlife. Hence, through eons and natural selection, waterfowl have evolved behavior to avoid intolerable conditions (e.g., cold and ice, food inaccessibility, disturbance, predation, etc.). They move from one location to find suitable habitats and resources elsewhere, ultimately to survive and produce offspring. Thus, most species of North American waterfowl endure the physical perils and energetic costs of migration each fall by leaving their breeding grounds and flying hundreds to thousands of miles to wintering grounds to survive and subsequently reproduce in spring.