Hawk Mountain Sanctuary has launched a four-year research effort to study northern harriers, asking Pennsylvania residents to help scientists better understand one of the state’s most vulnerable birds of prey.
The project, which runs from 2026 through 2029, will combine habitat analysis with satellite tracking technology to examine how the state-threatened grassland raptor uses Pennsylvania’s landscape.
Researchers plan to locate nesting pairs statewide and analyze verified sightings from eBird, the Pennsylvania Bird Atlas and Hawk Mountain’s Farmland Raptor Project database to understand how land cover, development and fragmentation affect harrier populations.
Scientists will also capture and tag adult or juvenile harriers with lightweight transmitters to map home ranges, migration routes and wintering grounds. The tracking data will show how the birds use the landscape throughout the year and whether development pressures influence nesting success and survival.
Northern harriers have experienced steep population declines in recent decades. Pennsylvania Bird Atlas data documented a 43% reduction in nesting distribution between the 1980s and 2010, while populations across eastern North America have declined by more than 30%.
“Northern harriers are one of Pennsylvania’s most unique and vulnerable raptors, but there is still so much we don’t know about their breeding ecology and habitat needs within the state,” said Bracken Brown, biologist-naturalist at Hawk Mountain Sanctuary on the Berks-Schuylkill County border.
“This project will help us identify what landscapes are most important for harriers and how we can better protect those habitats for the future,” Brown continued.
The birds nest directly on the ground in tall grasses or marsh vegetation, a habit that leaves them vulnerable to being mown over as these landscapes have been converted to hay fields. They require large expanses of open habitat to successfully raise young and serve as indicators of healthy grassland ecosystems that also support species such as bobolinks, dickcissels and short-eared owls.
Hawk Mountain is asking landowners and residents across Pennsylvania to report northern harrier sightings between May and July, particularly in areas with extensive grassland or marsh habitat.
Observers should look for a low-flying hawk with long wings, a distinctive white rump patch and owl-like facial features. Males are pale gray, while females are warm brown with heavily streaked chests.
“Because harriers are secretive nesters and can occur across large rural landscapes, local observations are incredibly valuable,” Brown said. “Landowners and community members can directly contribute to conservation simply by sharing sightings or information about historic harrier use on their property.”
Sightings can be submitted at hawkmountain.org/harriersighting. Inquiries can be directed to Bracken Brown at brackenbrown@hawkmountain.org or 570-943-3411, Ext. 103.
The research is supported through grants from the Pennsylvania Department of Conservation and Natural Resources Wild Resources Conservation Program and the Pennsylvania Game Commission, along with private support for tracking transmitters.
Purple martin sightings also wanted
A separate ongoing study is looking for sightings — and especially photos — of leg bands on purple martins, a swallow species, to be reported via this form.
Will Krohn, a graduate student at the University of Delaware, is leading the effort. He posted details to Facebook on Monday, June 1, about how the public can help.
East of the Rocky Mountains, the purple martin relies almost entirely on artificial housing for its nests, which can be found in the Lehigh Valley in areas like Minsi Lake and the grounds of St. Luke’s Hospital-Anderson Campus.
Krohn is leading an illustrated presentation this month in Allentown on the identification and life history of purple martins, and the ongoing research to help their populations. It’s scheduled for 7 p.m. Thursday, June 18, at the Shankweiler Science Building, Room 440S, of Muhlenberg College, 2400 Chew St. It’s free and open to the public.
