Sources and Sinks: Elucidating Mechanisms, Documenting Patterns, and Forecasting Impacts

A comprehensive understanding of source-sink dynamics can be critical for successfully managing at-risk species.We used field and modeling approaches to better understand the emergence and stability of sources and sinks and assess the implications of future system changes on population persistence. Modeling results identified the types of species and landscapes that are likely to exhibit strong source-sink dynamics and multi-species results indicated that management actions based on assumptions that sink habitats are generally harmful or helpful risk undermining conservation efforts. Black-capped vireo Vireo atricapilla field data and analyses documented source-sink patterns that were influenced by inter-annual variation and cowbird control on and near Fort Hood Military Installation in Texas. Most habitats outside of Fort Hood behaved like population sinks, and models indicated that persistence was sensitive to rates of inter-population exchange and the effects of future habitat restoration and climate change. Comparisons of black-capped and white-eyed vireos yielded insights into the unique limitations faced by black-capped vireos including a reduced breeding period and narrower use of habitat. This project highlights the importance of understanding source-sink dynamics in spatially-structured populations, as well as the need for applied source-sink theory and methods for conserving declining species in complex and changing landscapes.