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

• Published in: Ornis Hungarica
• Main Authors: Monneret, René-Jean, Ruffinoni, René, Parish, David, Pinaud, David, Kéry, Marc
• Other Authors: Moulin du Haut, Route du Vieux Mont 12, Bettenstrasse 51, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Swiss Ornithological Institute
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: Bayesian; BUGS; Dynamic occupancy model; colonization; detection probability; extinction; JAGS; Peregrine Falcon; persistence; territory; [SDE]Environmental Sciences; Jura; Falco peregrinus; peregrine falcon
• Online Access: https://hal.science/hal-02042406; https://doi.org/10.1515/orhu-2018-0016

International audience We summarize key results of the first 53 years of one of the longest-running avian population studiesin the world, on the Peregrine Falcon (Falco peregrinus), in the French Jura mountains (12,714 km2), launched in1964. A total of 449 cliff sites in 338 potential Peregrine territories were surveyed: 287 (85%) of these territorieswere occupied by an adult pair at least once, while in 51 (15%) we never detected an adult pair. Most sites werevisited several times during a breeding season to survey occupancy and later fecundity, but the proportion of sitesvisited was highly variable over the years. We highlight the power of the Bayesian implementation of site-occupancymodels (MacKenzie et al. 2002, 2003) to analyze data from raptor population studies: to correct populationsize estimates for sites not visited in a given year and for the biasing effects of preferential sampling (when bettersites are more likely to be checked). In addition, these models allow estimation and modeling of the site-levelpersistence 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 signalsfor subsequent population declines.Since 1964, the observed number of adult pairs varied between 17 in 1972 and 196 in 2008, but the proportionof sites visited increased from 43% in 1964 to 80–90% after 2002. Hence, this raw population total must be anunderestimate. We found strong evidence for preferential sampling in our study. Correcting for this, we estimated56 pairs in 1964, after which the population dropped to a minimum of 18 in 1972, but then recovered rapidly,leveling off somewhat around 1995 and reaching a maximum of 200–210 adult pairs during 2000–2012. This wasthen followed by a decline to 170–190 pairs. In any one year, the raw counts underestimated the true populationsize by 5–39% (mean 11%), due to sites not being visited (this correction ignores imperfect detection ...