A Metapopulation Model of the Peregrine Falcon in California: Viability and Management Strategies.

We modeled the Peregrine Falcon (Falco peregrinus anatum) population in California to determine its viability under different management strategies by modifying Lefkovitch stage class matrix models to include the introduction of captive-reared birds and the dynamics of two subpopulations linked by migration. The model projections using published parameter values indicated that the population would not sustain itself without supplemental introductions. Sensitivity analysis suggested that enhancing adult survivorship is more effective than enhancing fledging success to achieve a viable population. The model with connected subpopulations predicted fewer pairs than did nonspatial models and indicated that concentrating management efforts on the healthier, high-density population in northern California, rather than on the poorly performing population in central and southern California, would yield the largest overall population sizes. Fits of the model to yearly population data from 1980-1989 accurately predicted the size of the southern subpopulation, but slightly underestimated the size of the northern subpopulation, by six pairs. The model fit well when we excluded birds on newly discovered sites that possibly were active in previous years. Increasing northern adult survivorship to predict northern population sizes adequately led to a viable population exhibiting a source-sink relationship between subpopulations. Our results provide insight into the critical data to collect and the most successful strategies to execute in a management program, and give further indication of the importance of spatial structure to the dynamics of populations.