Peregrine falcons are circling back to Maryland Heights at Harpers Ferry

Peregrine falcons last raised young on the Maryland Heights cliff across the Potomac from Harpers Ferry in 1950, and nearly 70 years later the birds were showing interest in it again. The National Park Service tells the story of that nest site, the pesticide that emptied it, and the effort to bring the falcons back.

A female peregrine falcon at Harpers Ferry National Historical Park. NPS photo.

A famous nest, then none

When a pair last nested there, land was still being acquired for the new Harpers Ferry National Monument, restoration of the Lower Town buildings was just beginning, and the Maryland Heights hiking trail did not yet exist. A falconer who knew the site described a pair on the crag, the one with an advertisement painted on its face, hatching three chicks in 1950, two males and a female. The eyrie was then among the most famous in the eastern United States, known to falconers, egg collectors and naturalists and mentioned in several popular and scientific works, including Roger Tory Peterson's first full-length book, Birds Over America (1948). A book from 1895, A List of the Birds of Maryland, documents nesting on the Heights in the 1800s.

An entry from A List of the Birds of Maryland (1895), which documents peregrines nesting on Maryland Heights in the 1800s.

It was also the last productive peregrine eyrie known in Maryland. Through the mid-twentieth century the species vanished from the whole eastern United States, most of North America, the United Kingdom and Europe. The cause was reproductive failure from the pesticide DDT, an organochlorine that interfered with the birds' ability to metabolize calcium and led them to lay thin-shelled eggs that cracked before hatching.

Bringing them back

• 1970. Ornithologists and falconers started a captive-breeding program.
• 1975. Five years later, four captive-bred young were released from a tower inside the U.S. Army's Aberdeen Proving Ground on Carroll Island in the Chesapeake Bay.
• 1975 to 1984. In all, 90 falcons were released in Maryland, part of a continent-wide effort that released more than 6,000 captive-bred peregrines across the United States between 1974 and 1997.

Maryland Heights, known to have been occupied since at least the 1880s, was not an early release site, because young falcons freed at natural low-elevation sites without adult protection fell prey to great horned owls. So Maryland's releases, and most in the mid-Atlantic, came from towers on the Coastal Plain and from structures in cities, where there are fewer natural predators and plenty of small and medium-sized birds to eat. The hope was that the birds or their young would move inland to the natural cliffs. They did in the Northeast and parts of the southern Appalachians, where releases were at or near natural sites, but they have been slow to return to much of the rest of the Appalachian chain, and most eastern peregrines still nest on man-made structures or in cities.

Young peregrine falcons in a hackbox at Harpers Ferry. NPS photo.

In the late 1990s scientists at the Center for Conservation Biology at the College of William & Mary proposed taking young falcons hatched on bridges, where fledglings often drown or are hit by vehicles, and releasing them in vacant parts of the birds' historic mountain range. Harpers Ferry, Shenandoah National Park in Virginia and the New River Gorge in West Virginia were the three sites. About 30 falcons were released at Harpers Ferry between 2001 and 2005, in a partnership of the Center, the Park Service, the U.S. Fish and Wildlife Service, the Maryland Department of Natural Resources and others. None came back to breed there, but a male released at the New River Gorge in 2007 often visited the area and set up a territory in an active quarry in nearby Millville, West Virginia.

The most recent chapter

A peregrine falcon in flight at Harpers Ferry, spring 2019. NPS photo.

Sightings increased, but no falcon settled on Maryland Heights until 2015, when an adult female was seen regularly. Several adult males appeared that year and the next, but there were no breeding attempts. In December 2018 a local birder spotted an adult male using a ledge near the old faded sign. He drew a new female and the pair courted and explored ledges, but in early April the male vanished. Four days later a male peregrine's carcass was found at a nearby campground, with injuries consistent with a strike by another peregrine, and park officials guess it died in a territorial clash with a falcon from the quarry. The female and an immature male stayed into the summer, with no breeding attempts, and then dispersed. In late 2019 and early 2020 a new pair was seen hunting and defending territory.

A peregrine falcon on Maryland Heights, spring 2019. NPS photo.

How to help

Visitors can respect the seasonal closures, and the park invites volunteers to help monitor the birds or serve as educational interpreters, by contacting the park.

Sources

• National Park Service, Harpers Ferry National Historical Park, "Peregrine Falcons return to Harpers Ferry National Historical Park" (https://www.nps.gov/articles/peregrine-falcons-return-to-harpers-ferry-national-historical-park.htm); rewritten in hubnx's own words.