A DYNAMIC ANALYSIS OF NORTHERN SPOTTED OWL VIABILITY IN A FRAGMENTED FOREST LANDSCAPE

The Northern Spotted Owl (Strix occidentalis caurina) is closely associated with mature and old-growth coniferous forests in the Pacific Northwest. There bas been a rapid loss and fragmentation of this habitat over the last half century, which may jeopardize the long-term survival of the species through reduction of dispersal success. In this paper we report results of a population model for the Northern Spotted Owl that incorporates both juvenile dispersal and search for mates We analyze both deterministic and stochastic versions of the model in search of thresholds for population persistence related to search efficiency, population density, and amount of suitable habitat In addition; we analyze the model under the nonequilibrium conditions that currently exist due to timber harvest in the owls' preferred habitat. Our results predict a sharp threshold below which populations cannot persist, and suggest that inferences from population models that incorporate equilibrium assumptions may be highly misleading.