Survival rates of Northern Spotted Owls in post-fire landscapes of southwest Oregon

Abstract

We estimated annual survival rates (S) of 23 radio-marked Northern Spotted Owls (Strix occidentalis caurina) at the Quartz and Timbered Rock burns and adjacent areas in southwest Oregon. We used known-fate models in program MARK to test for differences in survival among three groups (owls dwelling inside of burned areas, owls displaced by wildfire, and owls dwelling outside of burned areas) and to investigate the potential effects of fire severity and cover type on survival. We found that annual survival rates of Spotted Owls that maintained a territory within the burn perimeter (Š = 0.69 ± 0.12) or that had been displaced by the burn (Š = 0.66 ± 0.14) were lower than those of owls that had territories outside but adjacent to the burn perimeter (Š = 0.85 ± 0.06). This result indicated that wildfire had a negative impact on Spotted Owl survival, at least in the short-term (i.e., 3-5 yr postburn). We were unable to identify a significant effect of fire severity or quantity of habitat on Spotted Owl survival, but this inability was likely related to our small sample size and high variability in habitat composition. We recommend long-term monitoring of survival on larger samples of owls to identify the effects of fire severity and habitat on Spotted Owl survival and to determine if wildfire poses a significant threat to the long-term persistence of Spotted Owls. © 2011 The Raptor Research Foundation, Inc.