THROUGH THE WOODS: Our magnificent osprey

WHILE DOING THE ALAN DEVOE Bird Club Century Run Bird Count on Saturday, the one where each birder tries to find 100 species of birds in one day, Marion Ulmer and I decided to checkout Stockport Landing at the end of Station Road. Both adult bald eagles were at their huge nest out on the island, and there were lots of fishermen on the Hudson River. Fish were running and an osprey was circling over the Stockport Creek. It dove and came up with a huge fish. It is amazing how much weight they can carry in their talons.

Suddenly one of the bald eagles attacked the osprey and grabbed its fish. This tactic of theft caused Benjamin Franklin to object to the eagle becoming our national emblem. The osprey is possibly North America’s best studied bird of prey, and the only raptor that eats almost exclusively live fish, and at times has been referred to as the fish hawk. Despite this restricted diet, Osprey have nested in a variety of habitats. Their prominent stick nests are found from mangrove islets of the Florida Keys to Alaskan lakes to New England salt marshes to the saline lagoons of Baja, Mexico, and from Carolina cypress swamps to the redwood coasts of California. All but southernmost populations are migratory, leaving their breeding grounds in late summer for rain forest rivers and fish rich seacoasts and lakes in Central and South America. Then they return north each spring as waters warm, and more fish become accessible.

Osprey. Photo by Nancy Jane Kern

An osprey nesting in central Quebec and wintering in southern Brazil might fly more than 125,000 miles in migration during its 15-to 20-year life. This makes the Osprey a very intelligent, hardy, and adaptable bird. Osprey dive feet-first for their fish, going down into the water to a depth of about three feet or less. This restricts them to surface schooling fish and to those in shallow water, with the latter most available. Because of this the North American osprey tend to breed in larger numbers where shallow waters abound. In many of these regions artificial nest sites have helped breeding pairs. Historically osprey built their nests atop trees, rocky cliffs, and on the ground if free of predators. While some continue to use natural sites, many have shifted to artificial sites such as channel markers in harbors and along busy waterways, on towers for cell phone and utility lines, and hundreds of nesting poles erected just for this species.

This shift has been dramatic in many regions, with about 90–95% of pairs choosing artificial sites. Factors causing this have been predation, loss of trees and development of shorelines. For several years, an osprey has been building a nest on a very tall power line tower at Schodack Island State Park. Last week the bird was back, and the nest looks like it will be a success.

During the 1950s–1970s populations were drastically decreased. About 90% of the pairs nesting along the coast between New York City and Boston disappeared during this period. Studies showed high levels of contaminants (especially DDT) in eggs, causing severe eggshell thinning resulting in poor hatching success. Osprey studies provided key evidence to help block continued use of long-lasting pesticides like DDT, and osprey populations have recovered. By the year 2000 many U.S. and Canadian populations were approaching historical numbers. The osprey is a survivor. I am so happy to find their fierce yellow eyes looking back at me from around our area, and to watch their spectacular dives into our waters. And maybe best of all, they have shown us what good care for our environment can do.

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