Objective

The spatial distribution and temporal stability of animal populations is a function of habitat quality, habitat selection, and dispersal. Source-sink dynamics--how local and regional processes structure populations and influence their persistence--comprise an essential aspect of population stability. Understanding source-sink dynamics for migratory bird populations is especially challenging and timely because these species move between multiple habitats and continents during their annual cycles, and many have declined in abundance over the past three decades. Multiple methods are available to investigate source-sink dynamics, each varying in degree of effort and expense. The Department of Defense (DoD), which manages nearly 30 million acres of high-value bird habitat, primarily uses the Monitoring Avian Productivity and Survivorship (MAPS) protocol to monitor avian populations and inform the management of bird species on its properties. However, the value of MAPS for quantifying avian source-sink dynamics at both local and regional scales has never been rigorously assessed or validated. This work focuses on the wood thrush (Hylocichla mustelina; hereafter WOTH), a DoD species at risk throughout its breeding range.

This project has three broad objectives. The first is to validate and test the efficacy of three methods to identify areas as sources or sinks: (1) dynamic and threshold occupancy modeling, (2) MAPS constant effort mist-netting protocol, and (3) intensive demographic studies of individually marked WOTH on breeding and wintering territories. Within this first objective, researchers will also use stable isotopes to independently validate the results of the above methods as well as provide data on the source of recruits and the scale at which source-sink dynamics operate. The second objective is to determine which local (e.g., cowbirds, microhabitat) and landscape (e.g., patch size, edge density) characteristics most reliably predict population growth trajectories (sources versus sinks). Third, researchers will use the empirical data collected in objectives one and two to construct predictive models of regional population persistence based on the number and ratio of source and sink patches in the landscape. This statistically rigorous, hierarchical approach will produce management strategies applicable to other migratory bird species and DoD installations as part of the larger Conservation Bird Management Plan.