Modeling Dynamics of Habitat-Interior Bird Populations in Fragmented Landscapes

Abstract: A stochastic computer model was used to examine the effects of varying degrees of habitat fragmentation on the dynamics of a hypothetical population of forest-interior bid. The primary demographic parameter that influenced the population's dynamics was fecundity, which varied as a function of how far a birds territory was from an ecological edge. As our model landscape became more fragmented the proportion of forest habitat that was near edges increased geometrically, and the population's overall fecundity dropped as a result. The model demonstrates that impaired reproduction in a fragmented landscape is, by itself a sufficient disruption of the population's dynamics to generate population declines and shifts in distribution similar to those observed in the fragmented forests of southern Wisconsin. Without immigration of recruits from other regions where reproduction is better, habitat-interior populations in a severely fragmented landscape can become locally extinct.