Ospreys -Spring 2018

by: Virginia Andrews

Coming from above, loud, emphatic.

Nothing embodies spring like the long, drawn-out call of a hovering Osprey. The return of this big charismatic bird of prey means open water and the turn of a new season.

Alone in the genus Pandion, the Osprey has returned in more senses than one. A long-distance flier that migrates deep into the jungles of South America to avoid the northern winter, it may have traveled as many as 2,000 miles over the course of a couple of weeks. Dodging storms, bucking unfavorable winds, catching food as it can along the way, each return is an athletic feat. The prize is a chance to raise a family, to ensure the species will go on.

With light-weight backpack transmitters, researchers have followed Ospreys as they migrate, as they fish in their winter homes, and as they use the waters of the north. Every successful year is a story of survival.

But it is not just a seasonal return. The Ospreys of New England have also come roaring back from near extirpation. Roger Tory Peterson watched them as they raised their young near his home in Lyme, Conn. through the middle years of the 20th century. Suddenly there was a precipitous decline. Prior to 1940, there were about 1,000 pairs nesting between Long Island and Cape Cod. By 1970 there were less than 100 in the entire region. Without warning, they had become unable to reproduce. Like any good scientist, Peterson and other researchers wondered why.Something, it seemed, had gone wrong with their eggs. The shells were too fragile to bear the weight of incubation by the adult. Some lacked shells altogether and were laid “sunny side up,” which however delightful as a breakfast order, is no good for embryonic development. With a series of observations and experiments, it was conclusively shown that the cause was environmental, tracked down to intensive aerial application of the pesticide DDT.

Used in attempts at mosquito control, the chemical remained in the environment. It did not readily break down, but became concentrated in the fatty tissues of living things. With each successive link in the food chain from minnow upward, the pesticide bio-accumulated, getting more concentrated at each step. As apex predators, Ospreys quickly accumulated a heavy dose. They were unable to metabolize the calcium needed for egg production.

They were certainly not the only birds to suffer, but their reliance on a fish diet made them more vulnerable. Studies showed DDT was also a potent human carcinogen. In 1972 its use was banned in the United States, although to this day it is still applied in other countries. But at that point the Ospreys of the northeast U.S. began their return from the brink.

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