Avian Demography in Mosaic Landscapes: Modeling Paradigm and Preliminary Results

摘要

The authors pursued a mechanistic explanation for the local extinction of some avian species from small and/or isolated patches in a habitat mosaic. A model was developed to simulate demographic processes of natality, dispersal, and mortality as these might occur in a mosaic of discrete habitat patches. These processes were adjusted to reflect life-history attributes that seem to confer sensitivity to habitat fragmentation. We used the model to explore the effects of restricted vagility and reduced natality resulting from biotic interactions for a hypothetical bird species. Restricted vagility resulted in local extinctions in small, isolated patches, but this effect was buffered by an available pool of surplus nonbreeders. Lower natality reduced this suplus so as to increase the frequency of local extinction, and allowed restricted vagility to play a more important role in affecting species distribution. Moderate levels of restricted vagility and reduced natality were synergistic in effect. In general, small patches in isolation tended to lose their populations permanently, large patches rarely suffered extinctions, but small and intermediate patches adjacent to other patches suffered extinctions and were recolonized repeatedly. The basic modeling approach can be expanded to include greater mechanistic detail, but implementation has been limited by a lack of appropriate data. Our preliminary results suggest which data are necessary to pursue a mechanistic, patch-scale understanding of species demography at the landscape scale. 17 references, 5 figures, 3 tables. (ERA citation 10:014449)