Mysterious Migration

Cooper's Hawk, adult © Rick and Nora Bowers/VIREO

Raptors usually start to return to Manitoba in February and continue to arrive in waves right through April. I was in Ecuador for much of this period; so, when I returned I couldn’t wait to get out and enjoy the show. When a clear, sunny day with south winds arrived, I dropped everything and headed for the St. Adolphe Bridge. At this site south of Winnipeg I can often see as many as a thousand or more hawks and eagles on a good day. This day was almost a complete bust. Six Bald Eagles, a Cooper’s Hawk, and a couple of Sharpies and Kestrels. Big whoop!

This, I discovered, was not unusual. The entire 2012 raptor migration season has been a bust in Manitoba. Far fewer Red-tailed Hawks, for instance, have passed over the St. Adolphe Bridge than ever before. At Windygates, in the Pembina River valley south of Morden and near the American border, the situation is more carefully monitored. Rigorous daily tallies from February through April indicate that 9,000 fewer raptors passed the observation points this year than in 2011.

Red-tailed Hawk adult, Western, dark morph © Greg Lasley/VIREO

These diminished figures have led to all sorts of speculation.

An unusually mild winter, with almost no snow accumulation, and an early onset of spring probably minimized the thermals that raptors rely on. Perhaps higher winds blew much of the straw and chaff off farm fields, resulting in fewer places for rodents to hide and a dearth of the usual stopover, refueling points for the raptors. Drought in the southern US, especially Texas, could also have affected migration.

American Kestrel adult female © Richard Crossley/VIREO

Whatever the causes, our raptors may have been hit by a triple whammy — displaced on their wintering grounds, contending with troublesome weather systems on their routes north, and spread out because of the lack of snow cover here, they may have altered their migratory routes or patterns or styles. They may be here and gone, having used non-traditional ways of getting into the province and farther north.

Or they may not be here yet. Or their numbers may have been dramatically reduced.

Only time will tell. What’s happened to the raptors in your area?

Gene Walz

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2 Responses to “Mysterious Migration”

  1. We live near St. Louis, MO. Most winters (to March), we see up to several hundred Bald Eagles along the Mississippi. This year – very, very few. It was a huge disappointment – we are avid eagle spotters. I have noticed a slight decrease in the number of Red-Tailed Hawks I see. I have noticed no change in the Kestrals, Cooper’s Hawks & Turkey Vultures.

  2. Ana Grace Schactman says:

    We live in a suburb of St. Louis and have a wild yard full of native plants and trees. This habitat attracts many songbirds, so Cooper’s Hawk and Barred Owls have made this the site for regular meals.

    In my travels around the city and county I constantly notice raptors on the wing, on light posts, and in tall trees. This year we have also noticed vultures flying over some areas of the city.
    Last fall, as I drove home one late afternoon, I saw a kettle of about 20 hawks over one of the inner ring suburbs. They may have been Broad Shouldered. It was hard to focus on the traffic with my head out the window, so I pulled over, and over, and over as they sailed overhead!

    The constant sprawl into rural areas around here has forced the wild birds and animals to adapt to urban living. Many of the park departments around the area have been planting native plants and trees, to hold soil and use less water, and to require less maintenance, and have thus, begun to create better habitats for many species of birds, animals and pollinators.
    This year, we are having a very early spring, with most trees and plants blooming before their normal time. My red buckeye is valiantly waiting for hummingbirds to come to pollinate it, and the dogwoods bloomed then dropped their flowers before the leaves filled in.

    I did hear that the mild winter did not force the Eagles to come as far south to fish. We always go to Riverlands Environmental Demonstration Area on the Mississippi flyway at Alton, Illinois in the winter. Sometimes a hundred eagles congregate below Dam #26 to feast in the churning open waters, when the river is frozen over. This year we only saw a few eagles, but there were some nesting on the bluffs up stream.

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