<ir temperature begins to drop and clouds blanket the sky with increasing frequency, some of us see the browning of leaves and steady disappearance of birds and other wildlife as a sign of the coming darkness of winter. Fall bird migration may not be the same inspiring sign of welcome change as spring migration, but it can be just as impressive. So if you find yourself out in the Arb walking, jogging, or just finding a place to enjoy the outdoors, try to notice some of the birds around you and think about what they might be doing here.
The most noticeable birds during the fall migration are the birds of prey. Hawk migration is already well underway. On any day Red-tailed Hawks, Northern Harriers, Cooper’s Hawks, Turkey Vultures, and other species can be seen flying over Arboretum prairies. Sunny days with winds from the north are the best time to spot migrating hawks because they rely on thermals, rising columns of warm air caused by the uneven warming of the earth’s surface and lower atmosphere, to keep themselves aloft as they cruise south to the warmer climes of Mexico and the American Southeast. The raptor migrations over the prairies are mirrored by Bald Eagle migration along the Cannon River. Bald Eagles nest just north and south of the Arb along the Cannon River and are seen frequently near West Gym and over the flood plain forests of the Lower Arb.
In winter, Bald Eagles gather in large concentrations along the Mississippi River near La Crosse, Wisconsin, and Bald eagles coming from the North and west follow the Cannon as a guide to locate the Mississippi River.
Songbirds tend to migrate in waves when the wind and weather conditions are favorable for long distance flying. Most songbirds migrate at night, and can fly for up to 400 miles without stopping if the conditions are right. How songbirds navigate during migration is complex, but like Bald Eagles, songbirds use waterways to guide their migration. The Mississippi flyway is one of four major North American migratory flyways, and if the wind blows out of the northeast in the fall, or the southeast in the spring, large “fallout” events can occur in which birds are blown from their main migratory flyways toward Northfield, where they will usually pause for a day or two along rivers and streams to replenish their stores of energy and continue their migrations.
While it’s already a bit late in the year for major fallout events, warblers can be seen on campus through the end of October along Spring Creek and the Cannon River. Watch for Orange-crowned, Blackpoll, Palm, and Yellow-rumped Warblers, along with permanent residents like White-breasted Nuthatches and Black-capped Chickadees throughout the fall.
If you need help identifying a bird you’ve seen in the Arb, checkout the Arb website’s bird identification resource at http://apps.carleton.edu/campus/arb/current. There should be an update for fall birds coming in the next few weeks.