Forest Preserve District of Cook County, Illinois
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Waterfowl Migrations
Nature Bulletin No. 615-A   October 30, 1976
Forest Preserve District of Cook County 
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Every autumn, McGinnis Slough -- a 315 acre sanctuary in our Palos preserves -- is visited by many thousands of waterfowl and provides some fascinating spectacles. Frequently, near sundown, flock after flock of ducks, coming from the north, set their wings and glide down upon the water. Meanwhile, other flocks are rising, circling, and then disappearing southwesterly toward the Illinois River Valley. Flocks of Canada geese, and sometimes a few whistling swans, also stop to rest and feed on this refuge.

The annual migrations of vast numbers of waterfowl have always awed and mystified mankind. When the sky is full of ducks as far as we can see, or when we hear a distant honking and discover a great V of geese overhead, we wonder where they came from, where they go, and how they find their way so surely back and forth, each spring and fall.

Some ornithologists like to believe that birds have a sixth sense -- a "sense of direction" -- which is absent or poorly developed in humans. Others surmise that they have "magnetic awareness " -- a sort of compass-like sense; or that they navigate by the sun. Still others insist that birds are guided by "inherited memory, " or "hereditary knowledge," or merely by a convenient "instinct. " None of these theories explains, satisfactorily, their behavior under all conditions. The manner in which birds find their way over thousands of miles of migration routes to their wintering grounds and back to the very spot where they nested or were hatched the previous year, continues to be a mystery.

Since 1885 the U. S. Fish and Wildlife Service has been accumulating information on the migrations of waterfowl. Much of it is based on the records of a great number of banding stations and other cooperators such as the Illinois Natural History Survey, and the Delta Waterfowl Research Station in Manitoba, Canada. Since 1910, several million ducks and geese have been banded and several hundred thousand "returns" have been received -- records of where and when banded birds were killed by hunters, captured by other banding stations, or recaptured by the original station in subsequent years.

This information established the fact that waterfowl, with few exceptions, move south and north between their traditional breeding places and wintering grounds through regular migration routes. Further, that there are four flyways in North America; the Atlantic, Mississippi, Central, and Pacific.

The Mississippi flyway is used by a great variety of ducks and geese with breeding territories that extend from the Dakotas and Wisconsin to the Arctic and from Hudson Bay to Alaska. Their principal wintering grounds are along the lower Mississippi and the Gulf coasts, although some birds -- notably blue-winged teal -- go to the West Indies or northern South America.

Cook County is located near the eastern edge of that flyway. During six years of trapping and banding ducks at McGinnis Slough, we demonstrated that black ducks from Ontario, as well as mallards and several other species from the north and northwest, stop here on their way to the Mississippi Valley. Also that blue-winged teal, from Saskatchewan and Manitoba, habitually stop here on their southeasterly migrations. Of 26,415 birds banded, and 3,393 reported as killed or captured, 659 had returned to McGinnis and been recaptured. Perhaps that is because we lie at the head of the DesPlaines and Illinois river valleys angling toward the Father of Waters. Perhaps this is a traditional stop-over learned long ago when so much of the Chicago region was swamp land. Nobody knows.

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