Global Warming?
Quite a few species whose winter ranges once ended just south of us are now
being seen more regularly or in larger numbers on the count. This trend is more
likely due to a change in seasonal distributions than to population increases.
Good examples are ..
Snow Geese,
Hooded Mergansers,
Common Mergansers,
Great Blue Herons,
Eastern Bluebird,
American Robin,
Fox Sparrow, and
White-throated Sparrow.
Rough-legged Hawk numbers have plummeted since the early eighties. This
species is a winter resident, so perhaps the recent milder winters have
resulted in fewer birds coming this far south.
West Nile Virus
American Crows suffered a dramatic decrease in 2002 which corresponds to the
arrival of the West Nile virus in northern Illinois.
Pheasants and Coyotes
Ring-necked Pheasants have undergone a gradual decline since the mid
nineties. This is probably due to an increase in local coyote populations which
occurred at about the same time.
Rising populations
Canada Geese dramatically increased their numbers through the eighties to
become the most abundant species in the count circle. Since then the numbers
have remained stable despite large year to year fluctuations.
Cooper's Hawk numbers have increased dramatically since the early nineties.
This reflects increased numbers throughout the year.
Both
Herring and
Ring-billed Gulls increased sharply during the early nineties.
Mourning Doves and
Red-bellied Woodpeckers increased their numbers dramatically in the late
nineties.
The House Finch Invasion
Purple Finches declined sharply in the late eighties this is about the time
when the closely related
House Finches expanded its range into the region.
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