Migrating swallows

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(Host) The return of the swallows to Capistrano is a well-known sign of spring. Commentator Ted Levin says that here in Vermont, when the swallows begin their migration south, it’s a sure sign of fall.

(Levin) August is a restless month. Birds are everywhere and busy. A few days ago, I saw a mixed flock of swallows – barns and trees and banks – feeding above the Connecticut River. They coursed low over the water, swept up as though caught by the wind, veered from side to side, then dropped down and repeated the entire process. Since each bird was engaged in a different phase of this feeding pattern, the swallows appeared chaotic, like ping pong balls bouncing all over the place.

After watching the flock for several minutes I realized that the swallows were not only cleaning the air of flying insects, they were drifting slowly south. Migration had begun. And it dawned on me that I haven’t seen a tree swallow swooping over our pasture for several weeks and the bank swallow colonies on the river are deserted.

All this activity does not portend an early autumn or a severe winter, it only reflects the impeccable timing of swallow migration. They leave as they always have, when the decreasing amount of daylight reaches a critical point, triggering a hormonal and physiological response that initiates what German ornithologists call zugunruhe, or migratory restlessness.

Migratory restlessness is characterized by both hyperactivity and the increased inability to rest at night. Birds engaged in migratory restlessness direct prodigious amounts of energy and time to a single activity – eating. The result is the accumulation of large deposits of fat just under the skin, fuel for the great flight ahead.

Swallows have already begun to build up along the outer beaches of the Atlantic Coast. Last week off the coast of Long Island I watched small groups of barn swallows trickle across Jones Inlet and skim over the rooftops of Point Lookout. They moved steadily westward toward New York Harbor.

Barn swallows winter from Panama to southern South America, one of the longest migrations of any North American land bird. Less inclined to jet set, tree swallows winter in the southern United States and Mexico. During mild winters they can be found north to Cape Cod, feeding on the waxy fruits of bayberry. When a cold fronts spills out of Canada, it pushes the tree swallows on the Atlantic Coast farther south, often to lands end.

Several years ago, I was in the Everglades when frost swept through, singeing the leave of tropical plants. The next morning thousands of tree swallows appeared above the rim of Florida Bay. I had not seen a single swallow prior to the cold front.

Today, the skies of Vermont are being drained of swallows, swept clean by elemental forces that dominate the Western Hemisphere. I don’t lament their passing; I only regret that while they were here, I hardly paid attention.

This is Ted Levin of Coyote Hollow in Thetford Center.

Ted Levin is a writer and photographer specializing in natural history. His most recent book is “Liquid Land: A Journey Through the Florida Everglades.” He spoke from our studio in Norwich.

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