Peregrines and Bridges
October 8, 2016
By Bryan Watts
In the flat lands of the Coastal Plain, bridges check two of the “like” boxes for peregrines, and many of the most famous bridges across the globe have been colonized as peregrines have recovered over the past forty years. In Virginia, the relationship began in 1992 when a pair of falcons settled on a bridge across the York River and produced two young. Since that time peregrines have used fourteen different bridges in the state and those bridges have made a significant contribution to the recovery of the population. Over the past ten years, bridges have accounted for 26% of the young peregrines produced in the state.
The Virginia Department of Transportation has been an essential partner in the recovery of peregrine falcons in Virginia. Both environmental and operational staff has adjusted maintenance schedules to accommodate falcon breeding, helped to maintain and relocate nesting structures, participated in annual monitoring, and assisted biologists in accessing and banding young. In 1998, the agency received the Federal Highway Administration’s Excellence Award in the category of Environmental Protection and Enhancements for their work to place peregrine nest boxes on bridges.
Although bridges serve as surrogates for natural cliffs on the Coastal Plain, they are lacking one feature compared to the real thing. Winds that flow onto cliff faces produce updrafts that young peregrines just on the wing use to buoy them back up to their eyries. Winds flow through the infrastructure of most bridges and do not produce updrafts. The difference appears to increase the chance that young, inexperienced falcons will circle down into the water or onto lower bridge structures. Beginning in 2000, a program was initiated to move some of the young from bridges to the mountains for release. The effort has the dual objectives of increasing survival and recolonizing the historic mountain range.
Peregrine falcon work in Virginia is a large partnership effort led by the Virginia Department of Game & Inland Fisheries, The Center for Conservation Biology, Virginia Department of Transportation, National Park Service, Dominion, The Nature Conservancy, NASA, and the U.S. Fish and Wildlife Service.