Osprey: Miracle of the 20th Century

Although the threat to Bald Eagles got most of the press, the Osprey was also headed for extinction due to habitat depletion and DDT. But Ecologist Paul Spitzer of Connecticut had a theory.

A great deal of biologist-naturalist Paul Spitzer’s life has revolved around the rhythms of one bird, the Osprey. In 1957, at the age of 11, he first visited Great Island in Connecticut. He was fortunate to have birding legend Roger Tory Peterson there helping with a Christmas Bird Count and Roger began mentoring Paul. This set him on a career path to becoming an ecologist.

After graduating from college he took up the question of what was behind the sudden, drastic decline in the Osprey population.

“At that time, the curtain was rising on the great DDT drama,” says Spitzer.

From the 1960s through the 1970s, Spitzer watched Ospreys almost dis­appear from Connecticut, and he pioneered experiments that helped establish DDT as a cause of their decline. He has also seen Ospreys make a triumphant recovery in the Connecticut River estuary. And with more than 300 ac­tive nests recorded in the state today, he is now turning his attention below the water, where the next challenge for Osprey is a vanishing fish.

He thought it was because pesticides made eggshells brittle. He got a permit to switch some Connecticut osprey eggs with Maryland Osprey eggs, where the DDT use was considerably lower, to see if the Maryland Osprey eggs stood up in Connecticut. They did.

The collapsing eggshells were connected to Connecticut poisons. Rachel Carson published her landmark book Silent Spring in 1962, calling on people to notice birds like the Osprey and to realize the damaging effect of pesticides. After Carson’s untimely death in 1964, both her words and her death became crucial messages about pollution and extinction.

Fast forward to 1972 when DDT was finally banned in the U.S., and osprey eggs slowly got stronger across several decades.

The Osprey’s next challenge was their food supply. This carried its own set of dangers, for the osprey to have fish to eat, the fish need to swim upriver to breed. But the dams in New England made upriver breeding nearly impossible. As a result, the fish began disappearing.

In the Osprey’s favor was once they had safe eggs and enough fish to eat, they are fearless in their nests. They nurture their young in plain sight, often on a platform or spindle in the middle of a bay or lake. You may have the pleasure of seeing these birds hunting with a rapid wingbeat and suddenly plummeting down to the water, snagging a fish and heading home with dinner for the kids.

DDT was first synthesized in 1874, but it wasn’t until Dr. Paul Muller, in 1939, discovered that DDT was extremely effective in killing insects. DDT was first used as an insecticide during World War II when it was used to kill mosquitoes. It was introduced for wide agricultural use in 1945.

DDT caused so much harm to some animals because the chemicals didn’t break down over time in the animals that ingested it. Every time an animal ingested DDT, it just continued to build up. This process is called biomagnification. This is when the amount of a substance found in an animal at the bottom of the food chain accumulates in ever increasing levels in animals higher on the food chain. Birds of preys, like the Osprey, that ate a lot of fish that had ingested DDT had more DDT in their system than any of the animals it ate because they stored the DDT from all of the animals they ate.

Over time, DDT made it more difficult for birds to absorb calcium and this lack of calcium made their egg shells thinner resulting in eggs breaking before the chicks could hatch. Because birds Ospreys typically only lay 1-3 eggs at a time, losing one or two eggs due to shell thinning had a dramatic impact on their populations.

Rachel Carson wanted research to be conducted that would ensure that pesticides were used safely. Congressional hearings were held, studies were ordered, and DDT was banned in 1972 by the Environmental Protection Agency after studies found that the chemical led to the thinning of eggs in some birds. It is widely believed that the publishing of Silent Spring marked the beginning of the modern environmentalist movement.

In the United States, in 1981, there were 8,000 breeding pairs of ospreys, by 1994 that number had risen to 14, 246 pairs and currently there are an estimated 19,000 breeding pairs.

We can thank Rachel Carson for sounding the alarm and Paul Spitzer for his research that made possible the miraculous recovery of these fascinating raptors.

Partially adapted from All About Birds

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Ross A. Feldner, RCC Board Member

Ross Feldner is the lead, with Bob Musil, of the RCC Bird Watch and Wonder Program. Ross is a life-long birder and photographer who is the editor of the Friends of Patuxent National Wildlife Refuge newsletter. Ross also serves as a guide at the Patuxent National Wildlife Refuge, a frequent birding spot for Rachel Carson who first learned about the health effects of DDT at the laboratory there. He is also the owner/art director of New Age Graphics, a full-service graphic design firm in Wheaton, MD.