Quest for food, refuge drives broad-winged hawk migration
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The day was autumn-perfect with a few high clouds, a brilliant azure sky, and a zephyr coming off the nearby Chesapeake Bay. We had just departed the Blackwater National Wildlife Refuge on a lovely late September afternoon. Soybean and cornfields were newly harvested. Pumpkins and apple orchards were just reaching their prime. For a few hours, the world’s troubles were forgotten.
As the road traced the edge of a loblolly pine forest, we spotted a raptor perched on a telephone pole. We eased the car onto the berm and pulled out binoculars.
The crow-sized bird looked like a wrestler, all compact power, its large head set close to its heavily barred chest. The belly, too, had messy rows of brown against a white background. The head was brown with a hint of red. The tail was short.
The hawk cast a look at us before flying along the edge of the forest and disappearing into it. The flight showed large black-and-white bands on the tail and short, broad wings.
The broad-winged hawk (Buteo platyterus) lives in the forest, just below the canopy. With incredible dexterity, it navigates the tangle of branches and undergrowth with ease. Here, it builds its nest, usually in the first big crotch of a mature tree. The mating pair produces one brood of up to five birds a year.
From this interior forest location, the pair sets up a territory that keeps them at least 1.5 miles distant from their nearest broad-winged neighbors. They need the area to feed themselves and their nestlings.
Voles, toads and frogs are favorite foods. The hunting hawk perches on a branch, or, as we had witnessed, on a pole adjacent to the forest edge. From that vantage, the hawk swoops down on its prey, which might include grasshoppers, crickets and caterpillars. Snakes and nestlings of other birds are also on the broad-wing’s diet.
More than half of all broad-wings breed and live for months in the expanse of woodlands that stretch from Alberta to Canada’s Maritime Provinces. Most of the remainder inhabit forests in the Eastern United States. A small percentage lives permanently in the Caribbean and parts of Mexico.
Broad-winged hawks overwinter in Central and South America. Each year, they migrate an average of 4,350 miles, one-way, to their southern homes. Their annual pilgrimage affords birders a bonanza of opportunities to see these handsome hawks.
As we watched the broad-wing disappear into the Blackwater forest, I pictured it on its migration, perhaps just days away.
Across thousands of square miles, broad-wings empty out of their territories. Previously isolated families join neighbors, searching for thermals — those rising columns of warmer air that form over heated lands. The hawks congregate in large kettles — swirling masses of raptors rising effortlessly on columns of warm air.
At Hawk Mountain, one of the nation’s oldest and most studied sites, thousands of raptors are counted each fall. There are scores of similar sites, like Waggoner’s Gap near Carlisle, PA, where 20,000 raptors of all species are counted annually. By the time all of these birds get to Mexico, the numbers are staggering.
At Veracruz, they are squeezed into a narrow, 30-mile wide corridor between mountains and the sea. There, vast cauldrons of raptors join in swirling, dizzying columns, rising hundreds and thousands of feet above the sunbaked 100-degree plains. Powerful updrafts lift birds until they finally give way to cooler air. Then, endless ribbons of raptors unspool across the Mexican sky, gliding for miles to the next kettle.
Biologists estimate there are 1.7 million broad-winged hawks alive today. Counts at Veracruz the last few autumns have recorded 1.4 million broad-wings each year.
Taking small cues from adjacent birds, raptors make tiny adjustments to their wings and tail to maximize their efficiency as they rise on fickle currents of air. These efficiencies are crucial. The broad-wings’ wide, rounded wings are ideally suited for the rapid twists and turns required of a forest dweller, not 4,000-mile migrations.
Relying on the collective wisdom of the kettle, broad-wings are able to effortlessly gain great heights and then soar for miles without flapping their wings. It takes weeks of 70-mile increments each year to go from a Blackwater forest to a winter home in the Amazon.
As the solitary broad-wing entered the loblollies, I knew that its quiet life would soon give way to the biological imperative to move to South America for sustenance and refuge.
Then, the world’s troubles started tugging at me again.
Across the globe, vast streams of migrants are on the move, too, refugees from harsh conditions, ranging from famine to endless violence. We marvel at the heroic annual flights of raptors across the landscape. But we should also respect the undaunted humans who face an equally challenging migration across the globe.
- Category: Wildlife + Habitat
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