Relation between Occupancy and Abundance for a Territorial Species,the California Spotted Owl |
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Authors: | DOUGLAS J TEMPEL R J GUTIéRREZ |
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Institution: | Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, , St. Paul, MN, 55102 U.S.A. |
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Abstract: | Land and resource managers often use detection–nondetection surveys to monitor the populations of species that may be affected by factors such as habitat alteration, climate change, and biological invasions. Relative to mark‐recapture studies, using detection–nondetection surveys is more cost‐effective, and recent advances in statistical analyses allow the incorporation of detection probability, covariates, and multiple seasons. We examined the efficacy of using detection–nondetection data (relative to mark‐recapture data) for monitoring population trends of a territorial species, the California Spotted Owl (Strix occidentalis occidentalis). We estimated and compared the finite annual rates of population change (λt) and the resulting realized population change (Δt) from both occupancy and mark‐recapture data collected over 18 years (1993–2010). We used multiseason, robust‐design occupancy models to estimate that territory occupancy declined during our study (Δt = 0.702, 95% CI 0.552–0.852) due to increasing territory extinction rates ( = 0.019 SE 0.012]; = 0.134 SE 0.043]) and decreasing colonization rates ( = 0.323 SE 0.124]; = 0.242 SE 0.058]). We used Pradel's temporal‐symmetry model for mark‐recapture data to estimate that the population trajectory closely matched the trends in territory occupancy (Δt = 0.725, 95% CI 0.445–1.004). Individual survival was constant during our study ( = 0.816 SE 0.020]; = 0.815 SE 0.019]), whereas recruitment declined slightly ( = 0.195 SE 0.032]; = 0.160 SE 0.023]). Thus, we concluded that detection–nondetection data can provide reliable inferences on population trends, especially when funds preclude more intensive mark‐recapture studies. Relación entre Ocupación y Abundancia en una Especie Territorial, el Búho Moteado de California |
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Keywords: | dynamic occupancy model population dynamics Sierra Nevada Strix occidentalis occidentalis temporal‐symmetry model diná mica de poblaciones modelo de ocupació n diná mica modelo de simetrí a temporal Sierra Nevada Strix occidentalis occidentalis |
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