On the Wing with David Gessner

The remarkable Osprey
What are those huge birds

Every year, Cape Cod's enormous and beautiful ospreys launch themselves on a precarious 8,000-mile round-trip journey to South America. A curious author joined them for what would be the ride of his life.

By David Gessner
"What are those huge birds" remarked a passenger on the ferry to The Vineyard.

I resisted playing the know-it-all. Ospreys, the only raptors that dive fully into the water for fish, were nearly wiped out in New England by our postwar use of the pesticide DDT. But we are in the middle of an osprey renaissance, and, thanks to their booming population and outgoing nature, the birds have become a visible presence on Cape Cod and other coastal areas. Ospreys are easy to observe at their large shaggy nests (they are pack rats, filling the sides of their homes with string, plastic bags, and, in the case of one Cape nest, a naked Barbie doll). But if you get too close, they might drive you off with a dive-bombing maneuver and their characteristic warning cries.

Because of the way the ospreys defend and commit to their nests, most observers think of them as homebodies. But there is another side to osprey life and another half of the year, during which “our” New England birds become world travelers. Ospreys are one of only six bird species to appear on every continent except Antarctica, and each September, they launch themselves on a precarious 3,000- to 4,000-mile journey to their wintering grounds on Amazonian rivers and Venezuelan lakes, returning north again in March.

I first got to know ospreys by studying them at their nests on the Cape, but I wanted to learn more about their hidden winter lives. So one year, instead of saying goodbye to the birds, as I had in the past, I followed them south on their epic migration down the East Coast to Cuba and beyond.

My trip kicked off on September 9, 2004, with a visit to a nest at Gray’s Beach in Yarmouth. As soon as I pulled into the parking lot and stepped out of the car, I heard it: the high-pitched kew kew kew that means osprey. Soon I was looking through my telescope at a bird standing on a nest above the marsh, ripping into a fish dinner. The bird’s brown-spotted necklace suggested it was a female, and its checkered feathering and orange eyes identified it as just-fledged. The bird’s huge talons pinned the flounder, and as it ate, it established a familiar osprey rhythm: dipping down to tear at the fish, then lifting its head back up before slurping strands of pink insides like spaghetti.

Born in May, this bird had emerged slimy, black, reptilian, no more capable of flight than a rock. Its transformation over the next month, from a miniature dinosaur stuck full of pinfeathers to an approximation of an adult bird, occurred at a pace that seemed like time-elapsed footage. That this awkward-looking creature had, after many clumsy attempts, learned to fly seemed surprising; that it had learned to dive for fish with any competence even more so. But that it was now, after barely earning its wings, ready to embark on a trip to South America and back, without the guidance of parents, was nothing short of astounding.

My original goal had been to follow the general course of osprey migration, not specific birds. But by happy coincidence, a North Carolina biologist named Rob Bierregaard had put satellite tracking devices on five birds on Martha’s Vineyard, so by simply checking the Internet, I could follow those individuals, too. Maps of osprey journeys show that their migrations are individualized to the point of quirkiness. For instance, a tagged bird that Bierregaard had named Tasha began her trip south the same day I did. Tasha was a youngster making her first migration, and she soon revealed her bold personality. Juveniles’ initial migratory flights are often tentative and short, but when Tasha took off from her summer nest on the Vineyard, she made a beeline south over the Elizabeth Islands and Buzzards Bay, keeping offshore and landing only briefly on Block Island before heading off again. Long Island would have been the natural place to rest, with plenty of good fishing nearby, but the winds were with her, and she must have felt the momentum of travel. She didn’t stop until she’d flown over New York City and crossed the Hudson to northern New Jersey.

Tasha could cover such long distances without exhausting herself because her mode of travel was one perfected by ospreys over millenniums: soaring. “Ospreys migrate for food,” says Keith Bildstein, a raptor authority and director of conservation science at the Hawk Mountain sanctuary in Kempton, Pennsylvania. “But they also do it because they can. Ospreys are built to soar.” Soaring allows raptors to move quickly and with relatively little energy from one good hunting ground to another, even if those hunting grounds are thousands of miles apart. To fly these long distances, the birds lift on columns of hot air called thermals, which form above treeless spots like beaches and parking lots, where heat rises off the earth. Or they use updrafts, which occur when wind hits the side of a mountain, creating a ski-jump effect. After the thermals and updrafts have lifted the birds nearly out of sight, they can pull in their wings and shoot forward for miles without having to expend effort by flapping.

But how does a young bird like Tasha first “get” the idea of thermals? Instinct, of course, but that’s too easy an answer. The popular birding writer Pete Dunne speculates that one way juveniles discover the phenomenon is simply by accident. Tasha might be flying along when suddenly she feels a little lift under her wings and – aha! – starts to understand. The elevator is going up, and she is on it. The next time may not be quite so accidental, and, according to Dunne, she may even keep an eye out for the airborne dust and rising debris that indicate a thermal. She may also be on the lookout for other raptors that have been scouting thermals.

In this manner, lifting and soaring, Tasha made her way along the coast to a barrier island in North Carolina, where near-hurricane winds forced her to lay low for a couple of days. Having watched ospreys on the marshes of Cape Cod during northeasters, I tried to imagine how Tasha would have responded to the storm. Though ospreys look large, their hollow bones give them little ballast; most actually weigh less than 4 pounds. Tasha would have flattened herself against the ground in a futile effort to avoid the winds, eyes squinting and feathers blowing back over her.

Migration is the most dangerous time of year, and for birds caught in the air – or worse, over the sea – during a storm, it’s all over. But when the weather lifted, so did Tasha. She rode tail winds to Bald Head Island, which became a launchpad for her long over-water flight to Florida, skipping South Carolina and Georgia entirely.

When Tasha arrived at Lake Okeechobee in south-central Florida, gathered gangs of ospreys let her know that she was on the right migratory track. She might have been forgiven if the warm weather, shallow waters, and abundant fish had tempted her to stay. But after a day or two, something prodded her to move again. On the afternoon of September 23, Tasha pushed off, leaving the United States behind. By the middle of the next day, she had put in another 190 miles and was flying down the mountainous green spine of Cuba.

My own mode of transportation was usually a rental car, not wings, but I took roughly the same route along the East Coast as Tasha. As well as watching ospreys, I watched osprey people, like the group of virtual birders I met on Long Island, part of a Web community that followed the daily (and nightly) life of a pair of osprey parents via a camera and microphone secured above their nest. By streaming continuous video on their computers, members of the group could eventually identify the cries of individual birds without looking. It was like Real World with ospreys, and as one member told me, “You get hooked on the plot and can’t stop watching.” Ornithology is one of the few fields in which amateurs can still make significant contributions, and this avid group had observed examples of active night behavior and sibling rivalry among osprey chicks that no scientist had noted before.

My goal had been to follow an osprey migration through Cuba, but I discovered that it was easier for a bird to enter that country than a human being, especially an American human being. By the time I managed to get a flight in, Tasha and the rest of Bierregaard’s tagged birds had already made their way across the island and down to South America. All except one. This bird, an adult male, had gotten a late start by staying on Martha’s Vineyard to feed his single offspring, which couldn’t seem to learn how to fish. Because it looked as if I might end up in Cuba at the same time as this dedicated father, I dubbed him Fidel and followed his daily travels.

Cuba is a central path in the greater osprey highway. Most other migrating birds, being hydrophobic, take the safer route to South America through Mexico, but ospreys use Cuba as their port of entry to the Caribbean. One of the people who helped discover this osprey route was Cuban scientist Freddy Rodriguez Santana. During my visit, we stood together atop La Gran Piedra in eastern Cuba and watched dozens of migrating ospreys stream overhead. The birds rode the updrafts of the Sierra Maestre, lifting and soaring past Guantanamo Bay and over to Haiti, before turning south and making the long over-water flight across the Caribbean.

It turned out that I had just missed Fidel in Cuba, but I followed him electronically as he headed to Colombia before crossing the equator and flying deep into the Amazonian watershed, nearly to Brazil. Then he stopped suddenly, on a small river, a tributary of the Rio Negro, a jungle world of vines and crocodiles quite different from his Martha’s Vineyard summer home. If he was like most adult ospreys, he would stay within just a dozen miles of this spot until late winter before beginning the trip back.

As well as tracking the birds online, I followed them physically throughout the year, including to Venezuela. Though I saw hundreds of ospreys during my trip, I never caught sight of any of the satellite birds Bierregaard had tagged. Tasha’s tracking device had stopped working over the Dominican Republic, so there was little chance I would ever see her. But I did finally catch up with Fidel in May 2005, back at his nest above the cliffs of Gay Head on Martha’s Vineyard. As I watched him through my telescope, I felt my own trip had given me some small understanding of the great cycle of exodus and return he had just undertaken. Though my adventure was over, Fidel was back where he had begun, already feeling the pressure of the year ahead, the need to mate and incubate so that his young could hatch and learn to fly and fish in time to make their own trip south. For me, this was an ending; for Fidel, it was just another beginning.

Excerpted from Soaring With Fidel: An Osprey Odyssey From Cape Cod to Cuba and Beyond, by David Gessner (Beacon Press, 2007). Reprinted with permission.
Mr. Gessner writes a blog for Cape Cod TODAY here.
He will be giving a talk and having his first Cape Cod book signing at the Cape Cod Museum of Natural History on June 2 at 2PM. Immediately following, all museum guests are invited to view the OspreyCam in the Marsh View Room where our resident Osprey couple will be expected to become parents.

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