MEXICAN SPOTTED OWLS USE FOREST MOSAICS AFFECTED by TIMBER HARVEST, INSECTS, and WILDFIRE

Abstract

Understanding how species of conservation concern interact with natural disturbances provides insights into their evolutionary environment and can inform land management and conservation planning. We examined the breeding season nocturnal space use (i.e., foraging ecology) of three Mexican spotted owls (Strix occidentalis lucida) in southern New Mexico, USA that occurred in areas previously affected by timber harvest, wildfire, and insect-related tree mortality, respectively. We found that individual owls (1) preferentially used the ecotone between forests that were harvested and those that were not; (2) avoided severely-burned forest but used areas with mixtures of different burn severities (i.e., 'pyrodiversity'); and (3) heavily used a small patch of insect-killed forest that resulted in extensive downed woody debris. In sum, forests characterized by a mixture of stand ages and stages, produced by various mechanisms, were consistently and preferentially used by Mexican spotted owls. Mexican spotted owl use of heterogeneous forest environments makes sense in light of historical disturbance regimes of this region, which were characterized by frequent lower severity fire events that generated spatial and temporal landscape heterogeneity.