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Historically, snow geese migrated across extensive grasslands and wintered in coastal marshes where they fed on roots and tubers of aquatic plants. While much of this coastal marsh habitat has been destroyed through development, agriculture - rice farming in particular - has grown tremendously, and provides an abundant and highly nutritious food supply.

At the LaPerouse Bay snow goose nesting colony, low fences exclude molting adults and goslings, allowing scientists to compare grazed and ungrazed areas. These exclosures have been in place for 13 years. Note lack of vegetation and topsoil outside the exclosures, where geese have removed virtually all plants.

This food source has increased overwinter survival and possibly even productivity. On the northern prairies an abundance of waste corn, wheat and other grains sets the table for high survival of young-of-the-year geese on their first migration south, and provides a ready source of nutrition breeding geese need to acquire en route to the arctic each spring.

Other factors may also be involved. Changes in long-term weather patterns in the arctic have been correlated with increases in production. Humans have provided countless refuges and management areas where migratory birds can feed and rest all across the continent. This "gravy train' of easy living has likely helped to increase survival rates and productivity. At the same time, waterfowl hunter numbers have declined and fewer geese are harvested each year.