COS 106-3 - Owl diets and habitat use in post-fire and salvage-logged landscapes

Abstract: Habitat alteration affects owls via loss of nesting opportunities, changes in thermal properties, and changes in prey abundance and distribution. For many owl species, we do not know the net effects of wildfire or post-fire salvage logging on populations. Post-disturbance landscapes may shift from vole-dominated communities to deermice (Peromyscus maniculatus), and ground cover may increase substantially as grasses and forbs dominate during early succession. Both prey abundance and ground cover affect foraging decisions by owls. Simultaneously, climate change may be detrimental to owls if hot days and nights make foraging more costly and as newly-opened habitats offer fewer thermal refuges. We use survey data, autonomus recording units, nest locations, and prey remains from pellets in multiple post-fire landscapes to examine (a) owl presence and location of nests in relation to disturbance; (b) owl diets in disturbed areas and in relation to prey abundance, and (c) thermal properties of habitats in relation to ambient temperature. Unsurprisingly, owl species vary substantially in their tolerance for habitat disturbance and the changes in prey abundance that result. Despite that, collectively we document that most owls avoid salvage-logged areas, many use even very recently burned areas, and dietary flexibility is common, even for species such as Short-eared Owls (Asio flammeus) with clear preferences for voles over deermice. Although these results suggest owls are resilient to fires, post-fire salvage logging appears to damage owls’ ability to use landscapes after fire.