Severe fire has impacted populations of the California spotted owl more than fuels management or drought-related tree mortality

Reducing fuel densities is the primary tool available to improve forest resilience to intensifying disturbance, but implementation is constrained by concern of effects to mature-forest associated species, such as spotted owls (Strix occidentalis). While the negative effects of severe fire on spotted owls are well studied, the influence of drought and fuels management on populations is uncertain, impeding fuels management. We integrated a novel dataset of California disturbance history with passive acoustic monitoring to compare the effects of severe fire, drought, and fuels management over 13 years on spotted owl occupancy across the Sierra Nevada, California, USA. Spotted owls were less likely to occupy 4 km² survey sites with a greater proportion of forest that burned at high severity and sites with a greater proportion of “heavier” fuels management (>25 % canopy reduction) but were insensitive to the proportion of “lighter” fuels management (<25 % canopy reduction) at sites. Across 7161 sites in the Sierra Nevada, severe fire resulted in an estimated loss of 482 occupied sites compared to only 65 lost from heavier treatments, owing to the limited implementation of fuels management in the region. Conversely, spotted owls were more likely to occur at sites containing a greater proportion of drought or other canopy reducing disturbance, presumably because of foraging opportunities facilitated by heterogenous forest conditions. Thus, recent severe fire has had a greater negative effect on spotted owls than fuels management, underscoring the potential benefits of increasing the pace and scale of fuels management for promoting both forest resilience and conserving mature-forest species.