Tracking Peregrine Falcons
Understanding bird movements and migratory routes is an important step toward recognizing potential threats
In the fall of 2010, BRI Biologists conducted raptor surveys on Monhegan Island in the Gulf of Maine. This island is a known by birdwatchers as a "hotspot" for migrating songbirds and raptors. In addition to counting and identifying over 800 migrating falcons and hawks (view summary), Chris Desorbo, BRI's Raptor Program Director, and his team captured and banded 17 peregrine falcons, 6 merlins (Falco columbarius), and 2 American kestrels (Falco Sparverius). Of these birds, two female peregrine falcons were fitted with satellite transmitters to document their migration route and future breeding grounds next spring. The map below depicts the movements through December 9, 2010.
In addition to the detailed information about individual falcon movements, Chris and his team counted and identified over 800 hawks and falcons from their perch on Monhegan Island. They found that at this island site there was a high proportion, nearly 75%,of falcon species (i.e. American kestrels, Merlins, and Peregrine Falcons) relative to hawks. This differs from other inland sites where hawks more routinely monitored.
Significance to Policy
BRI's ongoing studies of coastal migration patterns for nocturnal and diurnal raptors provide critical information about the numbers, timing, and species of birds migrating offshore. These types of data can inform future siting decisions for marine-based wind power facilities and other development.
More Information
Additional information from the 2010 diurnal raptor study will be available in 2011, including an analysis of local flight direction data from the study site, interpretations of stable isotope data yielded from feather samples (which can reveal information about the natal origins of migrants), and additional analyses of the timing and intensity of the raptor migration. The migration route of peregrine falcons fitted with satellite transmitters will be regularly updated on the BRI website. These transmitters will reveal the birds’ fall and spring migration routes, where they overwinter, and indications of where they were hatched.
Total counts of raptor species counted at Monhegan Island, Maine, fall 2010. Species codes: BAEA = bald eagle, SSHA = sharp-shinned hawk, AMKE = American kestrel, OSPR = osprey, NOHA = northern harrier, PEFA = peregrine falcon, and MERL = merlin. Not shown: 1 northern goshawk, 1 unidentified buteo, 1 unidentified falcon.
