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
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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Update: June 2012