Understanding the dynamics of spatially structured populations and their demographic components is of vital importance to the conservation of many threatened and endangered species in the face of on-going habitat loss and degradation. Over the past decade, there has been an increased emphasis on the importance of ‘connectivity conservation’ (e.g. restoring non-breeding habitat to increase structural connectivity) in lieu of efforts to improve the quality or size of existing breeding habitat. However, our understanding of the relative importance of dispersal versus local dynamics in maintaining population viability is limited, and the degree to which they should be prioritized for conservation remains a topic of intense debate. Our primary objective was to assess the direct contributions of dispersal (via immigration) and local demography (juvenile recruitment and adult survival) on observed population growth of a highly endangered population of snail kites (Rostrhamus sociabilis plumbeus) in Florida. We used over 18 years of band-resight data on snail kites where sampling covered two regions that comprise their entire known breeding range. Using reverse-time capture-recapture methods with multistate models, we estimated demographic contributions to population growth, (i.e. seniority parameters) at multiple spatial scales.
Results/Conclusions
Despite being a highly mobile species, the contribution of dispersal to regional population growth was minimal. The dynamics and demographic contributions varied significantly through time and between regions. Based on our results, local juvenile recruitment was the most important driver of local population growth, and is severely limiting the contribution of snail kites from what has historically been considered ‘critical’ habitat. Conclusions from this work help explain observed changes in snail kite abundance and can be used to guide conservation priorities for species recovery.