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A Blue View: How We Saved the Osprey

If you’ve ever visited the Chesapeake Bay, chances are you’ve seen an osprey—or at least spotted one of their conspicuous nests. But not too long ago, the osprey was a rare sight.

Published August 11, 2015


These large birds of prey survive almost exclusively on fish. Armed with sharp talons, they plunge feet-first into the water, grasping their meal and using their wing strength to lift the fish from the water.

When the pesticide DDT (dichloro-diphenyl-trichloroethane) was introduced in the 1950s, osprey populations drastically declined. Because it was affordable and effective at eradicating insects, DDT quickly became the pesticide of choice for many farmers. It seeped into the soil and inevitably made its way to the water.

Small animals absorbed DDT from the environment. Those smaller animals were then consumed by larger animals, with each consecutive animal accumulating higher levels of contaminants. This biomagnification meant species at the top of the food chain, like the osprey, experienced the greatest hardships.

The osprey’s rapidly declining numbers were a critical indicator of what was happening down the line of the food chain. Scientists were able to study the birds and identify DDT as the culprit, and by the '70s the pesticide was banned. Artificial nesting platforms were introduced, and the osprey population began to rebound.

Today, osprey nesting pairs are once again abundant throughout the Bay and its estuaries. They continue to act as a valuable indicator species, helping scientists monitor the health of our waterways.

Episode Transcript

If you’ve ever wondered whether it’s possible to make a positive difference for the environment amid all the doom and gloom we hear about every day, the answer is a resounding yes. Need proof? Here it is: The osprey.

Today, these fish-eating raptors are considered to be one of the Chesapeake Bay’s most iconic creatures, easily spotted between March and August nesting on channel markers, highway overpass signs, dead trees and artificial nesting platforms.

Locals hold a special place in their hearts for this species and for good reason: We nearly lost them. Osprey numbers crashed in the 1950s through the 1970s, wiping out 90 percent of the east coast population. They exist today solely because of individuals who took action.

Coincidentally, their decline also started with an individual: Dr. Paul Muller. Muller changed the world in 1939 when he discovered that a chemical called DDT was surprisingly effective in killing mosquitoes and other pests.

But as humans reaped the benefits of DDT, something sinister was happening in the food chain. DDT was being absorbed deep into the ground, and stormwater runoff was delivering it straight into waterways. Worms were consuming the chemical as they fed on nutrients in the soil, and small animals were absorbing it from lakes and streams. These creatures were then eaten by larger animals, which were eaten by even larger animals and on up the chain.

Soon, songbirds were dropping dead in yards. Birdwatchers observed troubling changes in bald eagle behavior and reproduction. Populations of certain species, including the osprey, began to diminish at alarming rates.

DDT was preventing ospreys from absorbing the calcium they needed to lay eggs with strong shells. As a result, many eggs broke before they could hatch.

That could have been the beginning of the end for the osprey—and other species—if it wasn’t for the actions of one person.

Biologist Rachel Carson had been researching the effects of pesticides on humans and birds at the time of DDT’s widespread use. She noted American robins and bald eagles were dying with high DDT concentrations in their bodies. In an effort to turn the tide, she published a book on her findings in 1962, titled “Silent Spring.”

The book spread like wildfire, igniting a national—and eventually international—debate about the environmental effects and regulation of synthetic pesticides. Though Carson didn’t live to see it, her activism changed the fate of many species and revolutionized industry regulations.

In December 1970, the U.S. Environmental Protection Agency was founded, largely in response to Carson’s book and the environmental movement that it inspired. Just two years later, the EPA banned the use of DDT in the United States. Other countries soon followed.

Here in Maryland, countless individuals boosted osprey recovery by building artificial nesting platforms, which served as ideal replacements for the trees lost through shoreline development. By 1973, nearly two-thirds of Chesapeake Bay ospreys were nesting on artificial structures like duck blinds, channel markers and manmade nesting platforms.

The rest is history. Osprey populations gradually recovered, as the number of breeding pairs in the U.S. rose from 8,000 in 1981 to over 14,000 by the mid-nineties.

Today, scientists estimate that the global breeding population of ospreys is around a half million and growing. Their story is living proof that the adage that naturalist Margaret Mead made famous: “Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it’s the only thing that ever has.”

To learn more about the osprey’s role as an indicator species, and to watch a live osprey cam, visit

A Blue View is produced by the National Aquarium for WYPR. For the National Aquarium, I’m John Racanelli.

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