Dynamics of Breeding-Season Site Occupancy of the California Spotted Owl in Burned Forests

• Published in: The Condor (Los Angeles, Calif.) Calif.), 2012-11, Vol.114 (4), p.792-802
• Main Authors: Lee, Derek E, Bond, Monica L, Siegel, Rodney B
• Format: Article
• Language: English
• Subjects: Animal populations; Birds; California Spotted Owl; Circles; Colonization; Coniferous forests; Demography; Endangered & extinct species; Environmental protection; extinction; Forest & brush fires; Forest fire detection; Forest fires; Forest habitats; Forest management; Habitats; Logging; National forests; occupancy; Ornithology; Owls; Polls & surveys; Probabilities; RESEARCH PAPERS; site-occupancy modeling; Strix occidentalis; Vegetation; Wildlife conservation
• ISSN: 0010-5422; 1938-5129; 2732-4621
• DOI: 10.1525/cond.2012.110147

Understanding how habitat disturbances such as forest fire affect local extinction and probability of colonization—the processes that determine site occupancy—is critical for developing forest management appropriate to conserving the California Spotted Owl (Strix occidentalis occidentalis), a subspecies of management concern. We used 11 years of breeding-season survey data from 41 California Spotted Owl sites burned in six forest fires and 145 sites in unburned areas throughout the Sierra Nevada, California, to compare probabilities of local extinction and colonization at burned and unburned sites while accounting for annual and site-specific variation in detectability. We found no significant effects of fire on these probabilities, suggesting that fire, even fire that burns on average 32% of suitable habitat at high severity within a California Spotted Owl site, does not threaten the persistence of the subspecies on the landscape. We used simulations to examine how different allocations of survey effort over 3 years affect estimability and bias of parameters and power to detect differences in colonization and local extinction between groups of sites. Simulations suggest that to determine whether and how habitat disturbance affects California Spotted Owl occupancy within 3 years, managers should strive to annually survey ≥200 affected and ≥200 unaffected historical owl sites throughout the Sierra Nevada 5 times per year. Given the low probability of detection in one year, we recommend more than one year of surveys be used to determine site occupancy before management that could be detrimental to the Spotted Owl is undertaken in potentially occupied habitat.