SPOTTED OWL METAPOPULATION DYNAMICS IN SOUTHERN CALIFORNIA

1. The California spotted owl Strix occidentialis occidentalis is foun d in the Sierra Nevada and in a series of isolated populations in the mountains of southern California. 2. We developed a model to assess th e risk of decline of the southern California spotted owl metapopulatio n. We modelled the spatial structure of this metapopulation by incorpo rating distance-dependent dispersal and correlation among the populati on growth rates. 3. Demographic characteristics of the largest insular population were estimated from colour-ringing the majority of the ter ritorial population. This owl population declined dramatically during the study period, 1987-93. 4. If the observed decline continues and si milar declines are occurring in the other populations, our viability a nalysis predicts that this metapopulation has a high risk of going ext inct in the next 30-40 years. 5. If the observed decline is due to nat urally occurring environmental fluctuations (drought), and thus tempor ary, the model results indicate substantial decline, but a low probabi lity of total metapopulation extinction. 6. Our results indicate that the risk of decline is quite sensitive to the correlations among popul ation growth rates. Increased correlation increased the risk of declin e.