The Peregrine population study in the French Jura mountains 1964–2016: use of occupancy modeling to estimate population size and analyze site persistence and colonization rates

• Main Authors: Monneret René-Jean, Ruffinoni René, Parish David, Pinaud David, Kéry Marc
• Format: Article
• Language: English
• Published: Sciendo 2018-12-01
• Series: Ornis Hungarica
• Subjects: bayesian; bugs; dynamic occupancy model; colonization; detection probability; extinction; jags; peregrine falcon; persistence; territory
• Online Access: https://doi.org/10.1515/orhu-2018-0016

We summarize key results of the first 53 years of one of the longest-running avian population studies in the world, on the Peregrine Falcon (Falco peregrinus), in the French Jura mountains (12,714 km2), launched in 1964. A total of 449 cliff sites in 338 potential Peregrine territories were surveyed: 287 (85%) of these territories were occupied by an adult pair at least once, while in 51 (15%) we never detected an adult pair. Most sites were visited several times during a breeding season to survey occupancy and later fecundity, but the proportion of sites visited was highly variable over the years. We highlight the power of the Bayesian implementation of site-occupancy models (MacKenzie et al. 2002, 2003) to analyze data from raptor population studies: to correct population size estimates for sites not visited in a given year and for the biasing effects of preferential sampling (when better sites are more likely to be checked). In addition, these models allow estimation and modeling of the site-level persistence and colonization rates, which can provide important clues about drivers of population dynamics, even without individually marking any birds. Changes in the dynamics rates may serve as early-warning signals for subsequent population declines.