The following post is part of the Raptor Blog Tour celebrating the release of Crossley ID Guide: Raptors. Make sure to check out all the really great articles about this superbly fine guide.
By early 1980s, the skies over Montana were missing the fastest aerial predator. The Peregrine Falcon had ceased to breed in a state where it was once considered common. The Peregrine population was at the tail end of a roughly 40 year decline that started with post-World War II modernization.
The post-war American was focused to better living through chemistry and technology, and removal of life’s nuisances was an intergal part of that utopian paradigm. Chief among the pests was the little blood-sucking, disease-carrying mosquito, and now we a had the tool to eliminate them from our lives. DDT and other chlorinated hydrocarbons were sprayed beyond liberally across the American landscape. Parks, irrigation canals, and wetlands were literally soaked with pesticides. The chemicals worked all too well, mosquitos and malaria sink from the forefront of the fearful American mind. But there lurked an unintended consequence of the introduction of these chemicals into the environment, a backwash that seeped unnoticed until a particular Silent Spring in 1962.
Organochlorine pesticides such as DDT are known to bioaccumulate within the food chain with top predators, like the Peregrine Falcon, being the termini of the process. DDT persists in the fatty tissue of an animal, and this property is the lynchpin of the accumulation. Bioaccumulation works somewhat like this. Say a mosquito possesses 1 unit of DDT, and a single nighthawk consumes 100 mosquitos in an evening of feeding. Now, the nighthawk has 100 units of DDT within its fat. Now a Peregrine Falcon kills and consumes 3 nighthawks over some time. That’s right, now the falcon has 300 units of DDT. Now the DDT does not outright kill the falcon, it causes eggs produced via ovigenesis to have reduced calcium in the eggshells. These thinner eggs tend to break easily in the nest. After a few diminished or failed breeding years, the recruitment of new falcons into the population falls below the rate dying falcons. Hence, the population slowly dwindles towards extirpation and, ultimately, extinction.
The alarm bells stated ringing in the 1960s, and the Peregrine Falcon was federally listed as endangered in 1970. DDT found itself banned from all use in the United States by 1972. But these efforts came too late for the native breeding Peregrine Falcons of Montana. Within decade, from 1970 to 1980, known falcon nesting sites (eyries) went from 23 to absolutely zero known breeding pairs within this huge, wild state. Luckily, the remedy for the disappearance was being implemented. The Peregrine Fund had been experimenting with the use of artificial nesting sites or hack towers and captive-bred falcons to augment existing populations. The hacking process, in a nutshell, involves placing near-fledging falcons within a hack tower, rearing them with minimal human contact, and hope they return to the site as breeding adults. The Centennial Valley and Red Rocks National Wildlife Refuge in southwest Montana were determined to be an ideal location for the beginning of the Peregrine Falcon reintroduction effort. By 1984, the first wild pair of Peregrine Falcons had returned to the Centennial Mountains, and this pair would continue to return to the site and produce young. Over the years, over 500 Peregrines were hacked at 26 different sites in Montana, and population slowly crept towards recovery. The number of known nesting sites now exceeds 50, and the now delisted Peregrine Falcon once again streaks through the Big Sky.
This post is part of the Raptor Blog Tour sponsored by Princeton University Press for its forthcoming release of The Crossley ID Guide: Raptors authored by Richard Crossley, Jerry Liguori & Brian Sullivan. I had the opportunity to review this new raptor field guide (forthcoming), and I to have to say that I loved this book. The composite photographic plates do a superb job in communicating the field marks, shape, habitat, and variations of all the raptors found in North America. The species accounts are vividly written and densely informative. This is how the Peregrine Falcon is described;
The chase is on! A Peregrine Falcon is closing in on its prey with blinding speed and precision turns. The smaller bird is quick and agile, but no match for the larger, faster, more powerful predator that mirrors its every move. Elegant, graceful, and deadly, the Peregrine Falcon is always one step ahead of its prey, typically outracing and capturing it in midair.
To read an outstanding review, head on over the Nemesis Bird for their review.
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