The Cause
There doesn't seem to be a single answer to explain the cause of this phenomenal
snow goose population growth. Much evidence suggests changes in winter food
availability is a primary factor.
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.
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.
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