The peregrine falcons of Dinosaur National Monument, 1972–2004

Craig, Gerald; Petersburg, Stephen

The decline and recovery of the American peregrine falcon (Falco peregrinus anatum) is one of the most profound success stories in the history of American endangered species conserva-tion. Dinosaur National Monument played a key role in that history. With the formation of the Rocky Mountain/Southwest Peregrine Falcon Recovery Team in 1974, Dinosaur National Monument became an integral part of the peregrine falcon recovery program. At that time, only eight of 22 Colorado nesting sites were occupied, one of which was in the monument. In-ventories were expanded throughout the state and intense remedial actions were taken to sus-tain productivity. By the time peregrines were de-listed nationally in 1999, Colorado’s popula-tion rested at 92 occupied sites with 14 residing in Dinosaur National Monument (NM). The recovery effort in Dinosaur NM was successful in large part due to the active and extended cooperation of the Colorado Division of Wildlife, National Park Service, The Peregrine Fund, Craig District of the Bureau of Land Management, U.S. Fish and Wildlife Service, and a host of contributed efforts. At the start of the recovery program, the northernmost breeding pair in Colorado occupied a territory at the confluence of the Green and Yampa rivers, near the center of the park. From 1977 through 1990, every eyrie that could be entered without un-due risk to personnel was manipulated to facilitate each pair’s breeding success. Thin-shelled eggs were replaced with plastic replicas and rushed to incubators at the Peregrine Fund. Then, captive, hatched chicks were returned and exchanged with the replicas, to be reared by each pair as their own. To augment captive production and provide additional young for release, pairs were recycled (induced to produce a second clutch of eggs), then treated as in the first case. Over the period of active management, 99 wild eggs were removed from Dinosaur NM eyries, 72 peregrine young were returned to these eyries, and 61 of these fledged successfully. An additional 30 young were released from hack sites (protective enclosures in which falcons are kept for several days before they are due to fledge); 20 of these successfully fledged. The eggs obtained in the course of foster efforts also provided information on shell thickness and pesticide residue trends for the pairs over 14 years. From one occupied territory in 1976, oc-cupancy increased to an average of about 13 pairs at 16 known territories by 1991, when active management efforts were curtailed. The population has since continued to increase. Future monitoring protocols and protective measures are recommended.