Peregrine Falcon Survival Rates Derived from a Long-Term Study at a Migratory and Overwintering Area in Coastal Washington, USA

Abstract

After a well-documented recovery following substantial population declines throughout most of North America, the Peregrine Falcon (Falco peregrinus) was delisted under provisions of the Endangered Species Act in 1999. Post-delisting monitoring for the Peregrine Falcon stipulated surveys of breeding locations and did not specifically emphasize other metrics of population dynamics such as survival. We used banding data from Peregrine Falcons captured on the Washington coast during 1212 vehicle surveys between 1995 and 2018 to assess apparent survival and resighting frequencies. Our mark-recapture data set included 226 Peregrine Falcons: 148 females and 78 males. Fourteen Peregrine Falcons were recovered dead and another eight were found injured or uninjured and unable to fly due to illness or substantially soiled feathers. We had 744 resightings, 67.1% (n = 499) by our research group during surveys (Group A) and 32.9% (n = 245) by others (Group B). We found a dramatic increase in Group B contributions beginning in 2008 due to the emergence of digital camera use in wildlife photography and increased public awareness of our project. Data from 1995 to 2018 supported the estimation of apparent survival for three age classes of Peregrine Falcons: 0.424 (SE = 0.057) for hatch-year ( 2 yr old). Our long-term mark-resighting analyses of overwintering and migratory Peregrine Falcons along the Washington coast provide evidence of a reasonably high level of apparent survival that suggests good population performance.