Excerpt: Living on the Wind
Follow a myriad of migrants on their winged journeys.
That would be remarkable enough even if the blackpoll took the most direct course. But it doesn't. Instead, like the American golden-plovers, they cross first a continent, and then an ocean. As August wanes, most of the Alaskan birds travel east, across the boreal forests of Canada, all the way to the Maritime provinces and the coast of New England. For a blackpoll born on the banks of the Alagnak, that alone is a journey of roughly 3,000 miles. While some of them then hug the shore toward Florida, it appears that many blackpolls strike out south over the open ocean, departing the Northeast coast at dusk, ordinarily picking a night with a brisk, northerly tailwind after the passage of a cold front. They will need the help. For the next forty or fifty hours, the tiny songbirds will fly over the western Atlantic, wings buzzing at twenty flaps a second, climbing to altitudes of more than 5,000 feet. They will show up on weather radar as they pass Bermuda and the Greater Antilles, glowing green specks that form diffuse blobs on the monitors, like ghosts beneath the moon.
The warblers follow a curving track, steered and abetted by the wind. At first, the northwesterlies carry them out to sea, the wind's push adding to the 20 miles per hour that the warblers can fly on their own. Midway, somewhere around Bermuda, the northwesterlies fail and the migrants come under the influence of the subtropical trade winds, which blow from the northeast. The tiny birds are shepherded back to the southwest, toward South America, finally making landfall along the coast of Venezuela or Guyana, an overwater trip of about 2,000 miles--a passage with no rest, no refueling, no water, during which each will have flapped its wings nearly 3 million times. "If a Blackpoll Warbler were burning gasoline instead of its reserves of body fat, it could boast of getting 720,000 miles to the gallon," note two researchers.
Nor are the birds finished; although some blackpolls do winter in the rain forests of northern South America, others continue south as far as northern Bolivia and western Brazil, another 1,500 miles or so. Then, in April and May, they reverse course, making a less-spectacular but still daunting traverse of the Gulf of Mexico or the western Caribbean and returning to their breeding grounds via the interior of North America. In all, the elliptical round trip for an Alaskan blackpoll warbler may cover eleven or twelve thousand miles.
I have seen blackpolls crowding the spruce woodlands of coastal Maine in late September, the gathered multitudes of the northern woods, and heard their slightly buzzy call notes in the dark as they set off over the sea, staking their lives on an exhausting journey through storm-raked skies. Knowing that some have already come from as far as the Alaskan Peninsula is humbling. Yet, to my thinking, the most astonishing of all the migrants that leave Beringia each fall are two kinds of long-legged shorebirds, the bristle-thighed curlew and the bar-tailed godwit, some of which cross not just part of the Atlantic but the entire width of the Pacific Ocean.
From LIVING ON THE WIND by Scott Weidensaul. Copyright (c) 1999 by Scott Weidensaul. Used by permission of North Point Press, a division of Farrar, Straus, and Giroux, LLC. www.fsgbooks.com