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Three major factors combine to influence
hawk migration in the Great Lakes
region.
Lakes
As the raptors move south from their eastern Canadian breeding grounds,
they are blocked by the north shore of Lakes Erie and Ontario. Thermals
do not form over water so the birds are forced in one of two directions:
east around Lake Ontario or west around Lake Erie. Those that move west
follow the north shore of Lake Erie, until they reach the mouth of the
Detroit River. Turning back is not an option so they are forced to cross
the 4-mile span to southeast Michigan, specifically Lake Erie Metropark
and Pointe Mouillee State Game Area. They lose altitude as they cross the
water, making it easier for them to be observed.
Thermals
Many species of raptors utilize thermals
to varying degrees during migration. Thermals are columns of rising
air caused by heating of the earth by the
sun. A bird will soar and gain altitude in
a thermal, set its wings, and glide to the
next thermal using little energy.
Weather
Weather is a key influence on hawk migration.
During the autumn months, cold fronts descend
from the north. After these fronts pass through
the region, a series of weather events fall
into place:
Light winds with a north component
Clearer skies
Increasing barometric pressure
Decreasing humidity
These factors combine to provide ideal weather
for hawk migration. Once the cold front passes,
it may be minutes, hours, or days, before
large flights can be seen.
Each of the three months of the hawk watch
has its own appeal.
September: Sheer Numbers
For those most interested in viewing sheer
numbers, September is the month
to visit.
Broad-winged Hawks pass through
by the tens
of thousands. The second and
third week are
the most productive, with the
peak centering
on September 19th.
Swainson's Hawks are expected
as well. Osprey
and Bald Eagles are seen almost
daily (whether
or not they are counted varies:
check our
protocols.). The majority of
migrant Sharp-shinned
Hawks and American Kestrels are
also seen
in September.
October: Variety
The pace shifts in October. Huge numbers
are unlikely, but the variation
in species
increases. Red-shouldered
Hawks, more Red-tailed
Hawks and more Cooper's
Hawks are observed.
Peregrines peak the first
week, while Turkey
Vultures are highest the
second week (thousands
in one day). On two occasions,
both in October,
all 16 regularly occurring
species have been
recorded.
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November: Worth the Wait
By November, species diversity is low, but
Golden Eagles, Northern Goshawks
and Rough-legged
Hawks make the chilly days worthwhile.
Where can I find the counter?
Sites for hawk observation shift due to changes in wind speed and direction. The following is a guide to help direct you to the correct site.
Lake Erie Metropark Boat Launch: used with west, northwest, north, northeast, east, and southwest winds.
Pointe Mouillee State Game Area Headquarters: used with northwest, north, and strong northeast winds.
The vast majority of hours logged by SMRR are from the LEMP Boat Launch. If in doubt, check there first.
Gear, Comfort and Conveniences
If you have a scope, bring it, but you'll
want binoculars, too. Dress appropriately.
Large temperature swings in a
day are possible.
In September, heat and humidity
can get high.
Conversely, November's cold winds
and snow
flurries can be bone chilling.
Comfortable
shoes make standing for hours
more bearable,
but a lawn chair is even better.
Parking
is available at both watch sites.
Heated
restrooms are available at LEMP
boat launch;
unheated at PMSGA. There are
no food concessions
at either site. Although local
restaurants
are within driving distance,
birds are notorious
for ignoring the lunchtime lull!
A sack lunch
with a thermos, hat, bug spray
and sunscreen
are all good ideas.
Choosing the right binocular.
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