Tracking fall migration across Southwest Montana

By Tyler Allen for explorebigsky.com

With a powerful pair of binoculars scanning the
northern skyline, wildlife biologist Brian Connelly
froze as he spotted a dark object above Ross Peak.
“Got one . . . Above the second knuckle of Ross,
coming in fast!”
The female Cooper’s Hawk took two strong wing
beats and within minutes was gliding powerfully
past Ross Peak, riding the thermal lift from a hot
September day, just before noon in the Bridger
Mountains.
For 21 years, the helicopter pad on the ridge at
Bridger Bowl has served as an observation deck to
track the fall migration of raptors through Southwest
Montana. Equipped with binoculars, keen
eyesight, and lightning-fast identification skills,
two wildlife biologists spend late August to late
October watching the flight path of North American
birds of prey.
Situated directly in a migration path called the Rocky
mountain flyway, the Bridger observing station will
count anywhere from ten to 100 raptors in a day. An
average of 2,400 birds of prey will fly over the Bridgers
during the fall migration, mostly seen between 10
a.m. and 2 p.m., when the heat of the sun creates the
greatest thermal lift. The more lift that birds take advantage
of means less energy expended during their
long journey south.
The Bridger site is one of many scattered throughout
the western U.S. Data collected here are compiled
with other locations (most of them administered by
an organization called Hawkwatch International),
to track changes in populations and species distribution
of migrating raptors. But the Bridger location is
unique for a number of reasons, one of them being a
very charismatic and very large bird: the golden eagle.
More golden eagles are counted over the Bridgers
than at any other observing station in the United
States. Over 1,000 of these impressive creatures,
which have a wingspan up to seven feet, are counted
here every fall. On their way to New Mexico, Texas
or northern Mexico from summer breeding grounds
in Canada, they’re visible with the naked eye soon
after they pass over Sacagawea Peak.
Two decades of observation here has shown a decline
in the population of these magnificent birds.
In the early 1990s, 1500-1800 golden eagles were
counted every season. Now the number of individuals
using this flight path has dwindled to just over
1,000.
This reduction is likely attributed to habitat loss in
their southern wintering grounds, with oil and gas
development playing a major role, says Steve Hoffman,
Executive Director of Montana Audubon and
founder of Hawkwatch International.
Something else that distinguishes the Bridger site
is its accessibility. The close proximity to Bozeman
allows it to reach a broader segment of the public.
Bridger Bowl ski area has played a helpful role supporting
this station throughout the years, allowing
access to the patrol shelter atop the ridge in case a
storm rolls in, as well as continued sponsorship of
the Bridger Raptor Festival every October.
While the public is welcome on the observation
deck any day of the counting season, Raptorfest
usually attracts 60-80 hardy hikers up to the ridge
during the second weekend in October. This annual
migration celebration educates and inspires families
in Southwest Montana. One of the biggest draws is
the allure of seeing live raptors – injured birds that
cannot be released back into the wild – in the hands
of bird biologists. This can instantly change the way
kids look at wildlife, and maybe change the way
they view and interact with nature for the rest of
their lives.
So with a pair of binoculars, and a sturdy pair of
shoes, you can join our local raptor experts this fall
as they watch one of this continent’s great migrations.