Spatio-temporal dynamics of wood warblers
Maintaining avian diversity in forest ecosystems have been shown to afford many benefits for forest health and productivity. However, alterations to the historical disturbance regimes within hemiboreal forests have impacted bird communities, and the ability of landscapes to meet the ecological needs of breeding forest birds has become a growing concern. As changes in forest landscapes continue, landscape effects may become increasingly important drivers of population dynamics for forest bird species. We used metapopulation theory as an interpretative framework to evaluate the characteristics of population dynamics and factors associated with local extinction and colonization for 22 wood warbler species over a 20 year time period. This approach allowed us to assess the complex spatio-temporal dynamics of warbler populations by directly addressing the underlying processes of local extinction and colonization. Research objectives included: 1.) Characterize long-term population dynamics in managed forests for 22 warbler species 2.) Determine the influence of patch size and edge at multiple spatial scales on probability of local extinction, 3.) Determine the influence of habitat composition, patch size, and edge at multiple spatial scales on the probability of colonization 4.) Assess the relationship of species life history and ecological traits as explanations for the observed occupancy dynamics.
Results of this study show long-term dynamics of 22 warbler species at large spatial scales were associated with species’ population density and habitat specialization. Landscape effects of mean patch size and total edge, as well as scale, on local extinction and colonization dynamics were species specific. Total edge was negatively associated with the probability of local extinction for nine species and mean patch size negatively affected local extinction probability for three species but the scale for the best models varied by species. There were no differences in life history or ecological traits among species that had landscape variables associated with local extinction models and those that did not. Mean patch size was a significant predictor of colonization probabilities for five species. Species that had landscape factors associated with colonization models were more likely to be generalist species and have higher densities. Further, the genus Setophaga showed a strong positive relationship between density and colonization probability, this suggests differentiation in dispersal rates may be a behavioral adaptation to decrease competition and therefore influence warbler community structure. Identifying mechanisms of species population dynamics at large scales is critical for understanding the ecology of these species, their population trends, and their conservation.