Identifying focus areas for multi-agency conservation efforts on landscapes that include Department of Defense (DoD) facilities is essential to protect military readiness and maintain populations of threatened and endangered species. Achieving this goal requires that there is knowledge of where species occur, when they move, and how their habitats might change over time. This information is lacking for most migratory songbirds, many of which have experienced significant population declines over the past century and are often too small to track with devices that record their movements across broad spatial and temporal scales. These data are critical because threats that impact any one part of a migratory species’ annual cycle can affect the entire population. The goal of this project was to demonstrate how remotely sensed data and miniaturized light-level geolocator technology (hereafter geolocator) could be used to help inform off-post landscape-scale conservation planning for small migratory songbirds that occur on DoD lands.

The project team used 0.41 g geolocators to examine the migratory behavior of a small (~10 g) endangered songbird, the golden-cheeked warbler (Setophaga chrysoparia, hereafter warbler). Remotely sensed data was also used to develop an updated winter habitat model for the warbler and to identify areas of highest risk of habitat conversion on the warblers breeding and wintering grounds. In addition, a web-based application was created that allows users to visualize the results and could help inform conservation planning during all stages of the species’ annual cycle.

The project team deployed 309 geolocators at five study sites across the warbler’s breeding range and used data recovered from 61 devices to examine the migratory movements of warblers. Eighty percent of warblers migrated from their breeding grounds in Texas and along the Sierra Madres to wintering grounds in southern Mexico and Central America, but 20% migrated over the Gulf of Mexico or traveled further east before arriving on their wintering grounds. Several areas along the warbler’s migration route and on their wintering grounds that were used by most birds tracked were identified. Locations outside the known winter range where warblers may occur were also found. The results suggested that warblers exhibit weak migratory connectivity, but given their relatively small winter range (~104,000 km²) and habitat losses forecasted to occur under optimistic scenarios (~43,000 km²), continued and increased conservation along the warbler’s migration route and on the wintering grounds are necessary to ensure population persistence and would simultaneously help protect co-occurring species of conservation concern. The web-based application developed includes movement data, habitat models, locations of formally protected areas, and projections for habitat loss.

This project filled critical knowledge gaps for an endangered species that occurs on DoD lands. The results could help inform future conservation efforts on the warbler’s breeding and wintering grounds, which is necessary to ensure population persistence and protect on-post training capabilities. The project team also demonstrated the use of miniaturized tracking technologies to study movements of small long-distance migrants. Such data are essential to slow and reverse continental-scale population declines of migratory songbirds, including several DoD mission sensitive species.