Raptor Recovery
DDT caused near-extinction of a number of birds of prey
Pesticides nearly wiped out a number of magnificent bird species in the mid-1900’s. Let’s be sure not to let history repeat itself …
Aerial spraying of DDT in 1955 (USDA photo)
DDT (dichloro-diphenyl-trichloroethane) is an insecticide. It was widely sprayed in the U.S. from the mid-1940s to the early 1970s. It was sprayed as a control for mosquitoes and for a wide range of agricultural pests.
Bald Eagle (by @chrisangphoto )
Starting in the late 1940s, many raptor species began to decline. The reasons for these declines were not yet known. This alarmed biologists.
Peregrine Falcon (by @raptors_etcetera)
Peregrine Falcons, Bald Eagles, and Ospreys were among those declining the most drastically. Before the 1940s, there were thousands of nesting pairs of Peregrine Falcons in the lower 48 U.S. states. By the mid-1960s, Peregrine Falcons were extinct east of the Mississippi River. Fewer than 50 nesting pairs remained west of the Mississippi River.
Bald Eagle pair (by @photographyandbirds )
Bald Eagles in the lower 48 U.S. states were also at the threat of extinction. By 1963, there were 417 nesting pairs of Bald Eagles in the lower 48 states. Ospreys were also experiencing a steep decline.
Brown Pelican (by @kwk_wildlife_photography)
Many other birds were on the decline as well. This included many songbirds, as well as pelicans, cormorants, and other waterbirds. The cause of these declines was still not clear…
Silent Spring by Rachel Carson
…that all changed with the publication of "Silent Spring" by biologist Rachel Carson. In this book, Rachel Carson detailed how DDT moves up the food chain. It dramatically affects those at the top of the food chain, including animals and humans.
Rachel Carson author of Silent Spring
"Silent Spring" warned of the dangers of pesticides, especially DDT, to wildlife and human health. Over 1 million copies were sold in the first two years alone. This single book is often credited with igniting the environmental movement.
Osprey at its nest (by @dan.gerstman )
Soon after, the main cause of raptor declines (and other species) was determined. The buildup of DDT in tissues of birds of prey caused them to lay eggs with thin shells.
Nesting pair of Peregrine Falcons (by @jessdeleonphotography)
Tragically, the thin eggshells often got crushed by the parents while incubating them.
Bioaccumulation of toxins up the food chain (from www.biologywise.com )
Indeed, the birds at the top of the food chain were those that were most drastically declining. As Rachel Carson had postulated, it was a food chain effect.
The chemical and pesticide industry tried to push back. But it was too late; the proverbial “cat was out of the bag”. The United States Environmental Protection Agency (EPA) banned DDT in 1972.
Sharp-shinned Hawk (by @raptors_etcetera )
Soon thereafter, populations of most of these birds of prey started to recover. They were far from being safe from extinction, but were on their way back.
Number of nesting pairs of Bald Eagles in the lower 48 U.S. states (by USFWS)
Many of these birds of prey received extra protections from the Endangered Species Act, passed in 1973. In 1963, there were just 417 nesting pairs of Bald Eagles in the lower 48 U.S. States. Now, there are over 70,000 pairs.
Adult Osprey at nest with its young (by @birdnerdnyc )
Ospreys experienced a similar recovery after the banning of DDT. In 1940, before widespread DDT spraying, about 1,000 Osprey pairs nested along the southern New England coast, between New York City and Boston. That dropped to 109 pairs in the early-1970s. Today there are more than 1,200 Osprey pairs nesting along that same stretch of coastline.
Peregrine Falcon (by @raptors_etcetera)
Peregrine Falcon recovery required a more hands-on approach. This was because DDT had wiped out all nesting pairs of Peregrine Falcons east of the Mississippi River. And there were relatively few remaining in the rest of the U.S.
In 1970, an organization named “The Peregrine Fund” began at Cornell University. This organization aimed to breed and raise Peregrine Falcons in captivity, then release them into the wild.
Peregrine Falcon (by @oceanrules)
From 1974 to 1997, the Peregrine Fund raised and released over 4,000 Peregrine Falcons into the wild. These, and related, efforts led to the Peregrine Falcon being removed from the Endangered Species list in 1999.
Peregrine Falcon (by @abrunophoto )
Today there are more than 3,000 nesting pairs of Peregrine Falcons in North America. Their recovery is one of the greatest wildlife conservation success stories to date.
American Kestrel (by @glen.noyer)
Most U.S. birds of prey have recovered well from the DDT declines. Some, like the American Kestrel, however, have not recovered to pre-DDT population sizes.
Red-Tailed Hawk (by @sarahkeatesnature )
A similar current issue facing raptors is secondary poisoning by rodenticides. This happens when they prey on rodents that ate a specific type of rodent poison, called “SGARs”.
Barred Owl (by @ncbirdwatch)
In 2015, the federal government banned retail sales of SGAR rodenticides. They are banned because of the risk they pose to children, pets, and wildlife. However, commercial pest control companies still widely use them and can buy them.
Short-tailed Weasel (by @tg_wildlife)
This secondary poisoning of raptors by rodenticides can lead to internal bleeding, organ failure, paralysis, and death. Similar secondary poisoning also occurs in other rodent predators. This includes foxes, domestic cats allowed to range outdoors, coyotes, weasels, and others.
How You Can Help
If you are run a business which has a rodent problem, don’t use SGARs nor hire pest-control companies that use SGARs.
Spread the word about harmful effects of rodenticides with others.
Advocate for wildlife: Become part of an organized campaign (such as these in Massachusetts) in your state to ban the commercial use of these SGAR rodenticides.
Support rehabbers: Consider donating to wildlife rehabilitators; many of them help rehabilitate raptors and other wildlife that have been impacted by these rodenticides.