A LITTLE OSPREY-TALITY GOES A LONG WAY - From Florida's Sanibel Island to Oregon's Willamette Valley, people are putting out the welcome mat for ospreys and the birds are flourishing

National Wildlife, Oct-Nov, 2001 by Doug Stewart

STANDING IN A SKIFF alongside a towering bald cypress tree in the shallow waters of central Florida's Lake Istokpoga, biologist Mike McMillian grips one end of a climbing rope. High above, clipped onto the other end, is a woman named Lourdes Rojas, decked out in rock- climbing gear.

McMillian and Rojas are researchers at Florida's Archbold Biological Station, a private nonprofit research facility. In the past decade, they have banded more than 500 ospreys as part of a study of the birds' breeding and travel habits. On this day, Rojas is preparing to reach into a huge osprey nest at the top of the cypress and extract a pair of chicks hunkered down inside, ringed by fish skeletons. Mom and Dad don't like this one bit. They sweep in tight circles just over Rojas' head, peep-peep-peeping in protest.

"That's the female," says McMillian of the larger, closer adult. "See that dark band across her chest? If one of them goes after Lourdes, it'll be her." The ospreys now stop peeping and start honking their "I'm-mad-now" call. Rojas is unfazed as she gently places chick number one inside an old pillowcase.

"I had an adult throw a fish at me last week," she yells down while lowering the pillowcase on a rope to McMillian. "That was a first."

The osprey is one of wildlife biology's great success stories in this country. From remote Lake Istokpoga to the sandy tourist mecca of Sanibel Island in Florida, and from the Chesapeake Bay to Oregon's Willamette Valley, osprey populations in the United States are growing, in some cases spectacularly. In the 1950s and 1960s, the eggshell- thinning effects of DDT devastated the raptors' numbers in North America. But with the chemical banned, osprey populations since the early 1980s have more than doubled in many regions. Today, by some estimates, more than 15,000 breeding pairs of the birds range throughout the nation.

Few raptors are as charismatic as ospreys. With their huge nests and dramatic fish-hunting skills, they're easy to identify and watch, and relatively tolerant of human activity. In fact, they've come to rely on human activity--in particular, the erection of artificial structures on which to build their giant nests (which makes observing them that much easier). Human interference, which nearly wiped out the species, is now helping it flourish again.

Ospreys, or fish hawks, inhabit every continent except Antarctica. In this country, roughly half of the birds nest along the East Coast or the Gulf of Mexico. The Chesapeake Bay alone hosts roughly 1,500 breeding pairs. Other large populations of the raptors are found in the Pacific Northwest, in the Northern Rockies (where they feed on reservoir fish) and near the Great Lakes.

If ospreys have a utopia, it could be Lake Istokpoga, home of what may be the densest concentration of nesting ospreys--more than 700 at last count--in the world. The 28,000-acre lake's undeveloped shores are lined with majestic, moss-draped bald cypress trees, and one after another holds an osprey nest--sometimes two. The trees' relatively sparse upper branches offer an unencumbered nest site with a 360-degree view. The heavily buttressed trunks are surrounded by water, which repels raccoons as effectively as a castle's moat. The lake, moreover, is shallow and teeming with large fish. Ospreys, unlike pelicans and many other fish-eating birds, dive feetfirst and so have to nab fish swimming near the surface or in shallow water. Because ospreys haul their catch home one at a time--in their talons, not their mouths-- small fish aren't worth the chase.

In the skiff, McMillian gingerly examines the day's first osprey chick. Warm and fishy smelling, the nestling calmly appraises its captor with large orange eyes. The chick is perhaps five weeks old, yet already weighs close to four pounds, as much as a typical adult. This is one well-fed baby. "If I were holding an adult like this, I'd be ripped to shreds by now," says McMillian. Two or perhaps three nestlings are a typical brood for ospreys.

In general, ospreys like to build their nests in the tops of dead trees, if any are available. (In marshes or on small islands where raccoons, great horned owls and other predators are absent, ospreys may nest in low trees or even on the ground.) Nests are an impressive tangle of sticks, sometimes reinforced with the odd bicycle tire or bit of fishing net. A big nest can weigh half a ton.

Difficult to build, a nest is typically maintained and enhanced year after year by the same pair of birds. But this doesn't mean ospreys mate for life. "It's probably more accurate to say each individual is attached to a nest and defends it against others of its own gender," says Mark Martell of the University of Minnesota's Raptor Center. "It may not make much difference to either bird if the same partner comes back or not." What's important is hatching eggs.

Osprey pairs don't migrate together. Males and females head south in the fall at different times and go to different places. For six years, Martell has followed the travels of more than 100 ospreys that he fitted with satellite transmitters. "The big surprise has been in South Florida," he says. Ospreys there were thought to stick around all year, enjoying the fish and warm weather. Some do indeed stay in the area. "But it turns out," he notes, "that some go to Bolivia and Brazil."