Territory occupancy and breeding success of Peregrine Falcons Falco peregrinus at various stages of population recovery |
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| Authors: | Michael J. McGrady James E. Hines Chris J. Rollie George D. Smith Elise R. Morton Jennifer F. Moore Richard M. Mearns Ian Newton Oscar E. Murillo‐García Madan K. Oli |
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| Affiliation: | 1. International Avian Research, Krems, Austria;2. United States Geological Survey, Patuxent Wildlife Research Center, Laurel, MD, USA;3. RSPB, Scotland, Old School, Crossmichael, Castle Douglas, UK;4. Scottish Raptor Study Group, Kirknewton, West Lothian, UK;5. School of Natural Resources and Environment, University of Florida, Gainesville, FL, USA;6. Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, USA;7. Conansknowe, Kirkton, Dumfries, UK;8. Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford, UK |
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| Abstract: | Organochlorine pesticides disrupted reproduction and killed many raptorial birds, and contributed to population declines during the 1940s to 1970s. We sought to discern whether and to what extent territory occupancy and breeding success changed from the pesticide era to recent years in a resident population of Peregrine Falcons Falco peregrinus in southern Scotland using long‐term (1964–2015) field data and multi‐state, multi‐season occupancy models. Peregrine territories that were occupied with successful reproduction in one year were much more likely to be occupied and experience reproductive success in the following year, compared with those that were unoccupied or occupied by unsuccessful breeders in the previous year. Probability of territory occupancy differed between territories in the eastern and western parts of the study area, and varied over time. The probability of occupancy of territories that were unoccupied and those that were occupied with successful reproduction during the previous breeding season generally increased over time, whereas the probability of occupancy of territories that were occupied after failed reproduction decreased. The probability of reproductive success (conditional on occupancy) in territories that were occupied during the previous breeding season increased over time. Specifically, for territories that had been successful in the previous year, the probability of occupancy as well as reproductive success increased steadily over time; these probabilities were substantially higher in recent years than earlier, when the population was still exposed to direct or residual effects of organochlorine pesticides. These results are consistent with the hypothesis that progressive reduction, followed by a complete ban, in the use of organochlorine pesticides improved reproductive success of Peregrines in southern Scotland. Differences in the temporal pattern of probability of reproductive success between south‐eastern and south‐western Scotland suggest that the effect of organochlorine pesticides on Peregrine reproductive success and/or the recovery from pesticide effects varied geographically and was possibly affected by other factors such as persecution. |
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| Keywords: | multi‐state multi‐season occupancy models nesting success pesticide‐related population decline population dynamics reproductive success territory occupancy |
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