Two studies published in the September 2020 issue of The Journal of Raptor Research have expanded our understanding of the migration and population stability of the Peregrine Falcon.
The first, from Oscar Beingolea and Nico Arcilla of the International Bird Conservation Partnership, reports that Peregrines banded at their North American breeding or natal sites or during migration all flew to Peru for the winter.
Eight falcons banded at breeding sites from Alaska to Nunavut to Minnesota and Nebraska between 1963 and 2016 all were later found at sites in Peru, the study shows. And 13 falcons banded at migration sites in Texas and along the East Coast also turned up in Peru. A bird from Alaska traveled the farthest — 6,630 miles (10,671 km).
The findings suggest that falcons of two subspecies, Falco peregrinus tundrius and F. p. anatum, “winter in Peru and originate from a widespread geographic breeding range, corroborating other research suggesting that Nearctic peregrine migration is highly dispersive,” the researchers write.
The second study examined the stability of the Peregrine population along the Pacific coast of the southwestern portion of Washington state. A team of researchers led by Daniel E. Varland captured and banded Peregrines from 1995 to 2018.
Based on years of resightings of falcons along the area’s beaches, Varland and his colleagues say the birds have “a reasonably high level of survival that suggests good population performance. This is corroborated by our finding that the observation rate of Peregrine Falcons was stable across the 22-year study.”
The researchers note that other observers began to report more resightings of falcons starting in 2008, a year that coincides with the “emergence of digital camera use in wildlife photography and increased public awareness of our project over those years.”
Varland also reports that mercury levels in Peregrine feathers in his study “are among the highest reported for the species” but that the contaminant levels did not seem to affect survival.
Post updated: We clarified the last sentence regarding the effects of mercury on the falcons.