By Christine Gianas Weinheimer EBS CONTRIBUTOR
YELLOWSTONE NATIONAL PARK — Humans have long been fascinated by birds of prey. Their graceful passage through the sky, hunting prowess and impressive wingspans make them awe-inspiring to watch. Luckily for us, a great time and place to see raptors on the wing is autumn in the Greater Yellowstone Ecosystem.
Increasingly colder temperatures and shorter days trigger the
birds’ instinct to migrate from this area in late August or early September and
continuing through early October. You’ll see resident birds migrating as well
as those passing through on their route between their nesting territories and
their winter ranges in the southern United States, Central America or South
America.
The north-south ridges of the Bridger and Gallatin mountain
ranges are ideal places to witness the fall migration of hawks, eagles and
other raptors, as are the wide-open valleys of Yellowstone National Park. The park’s
Hayden Valley is a popular destination to view birds of prey, especially Swainson’s
hawks.
We asked Brad Bulin, senior naturalist for the Yellowstone
Forever Institute, for some tips on viewing the fall raptor migration in
Yellowstone and the surrounding area. He said that knowing a little about how
birds migrate will provide you with clues as to the best places and times to
see them.
“Most raptors migrate during the daytime, when thermals—or
columns of rising air—form as the sun warms the ground below,” Bulin said,
adding that the birds “ride” these thermals, enabling them to conserve a great
deal of energy as they gain altitude without flapping their wings.
Because air currents rising up the side of a mountain are particularly
strong, large numbers of raptors roughly follow the north-south ridges of the Continental
Divide as a migration corridor.
“Afternoons tend to be better than mornings, after the wind
picks up. Right after a storm comes through is probably the best time. During a
cold front, the winds blow counterclockwise,” he said. “That north-to-south
wind direction is exactly what the raptors need.”
When in Yellowstone, he suggests positioning yourself anywhere
with a wide-open view of the sky. “Hayden Valley, Dunraven Pass, Mount Washburn
and Swan Lake Flats are all located along migration routes and are good places
to spot raptors,” Bulin said.
He advises using binoculars and constantly scanning the sky
and ridgelines, as well as tall trees. “If the weather is not conducive to
flying—if it’s raining or there’s very little wind—look up in the trees to spot
raptors waiting to continue their long journey south.”
Christine
Gianas Weinheimer lives in Bozeman and has been writing about Yellowstone for
17 years.
