Tracking the Golden-winged Warbler
A gorgeous splash of lemon yellow graces the cap and wings of the male Golden-winged Warbler, and pictures can’t do it justice – it has to be seen in the field to feel its full impact. And by ‘the field’, we mean that literally, as this declining species is a bird of open habitats such as old fields and shrubby pastures; these are habitats that host a variety of other ‘young forest’ species that are also losing ground, including Field Sparrow, Brown Thrasher, Yellow-breasted Chat, and Bobwhite quail. The golden-wings’ habitat requirements are very specific; the open lands in which it nests are found in heavily forested landscapes at mid- to high-elevations. In Virginia, the bird’s range is restricted to the high valleys of the western, mountainous part of the state.
Golden-winged Warblers are already returning back to their Virginia breeding grounds, after spending their winter somewhere in Central or northern South America. But exactly where do Virginia golden-wings winter? This is the subject of an ongoing study that will have field technicians from Virginia Commonwealth University (VCU) busy catching golden-wings at sites in Highland and Bath Counties for the next month. The study is funded by Virginia Department of Game & Inland Fisheries (DGIF) who, with VCU and other partners like The Nature Conservancy, is collaborating on a multi-state project to learn more about the migratory routes and wintering sites of Golden-winged Warblers. While factors on the species’ breeding grounds are contributing to its wide-scale declines in the Appalachian region, better understanding the challenges that it faces across its full life cycle across two continents will help researchers to more effectively target the necessary conservation actions.
At this same time last year, VCU techs caught 23 golden-wings (and 2 hybrid warblers) using mist nets, placed aluminum and colored plastic bands on their legs as identifiers, and outfitted them with a harness carrying a tiny geolocator. This device records light levels (to determine timing of sunrise and sunset) that will allow researchers to roughly calculate the coordinates marking the daily location of each bird throughout its fall migration, the winter, and its subsequent spring migration back to Virginia.
Geolocators are are a a low-tech substitute for the satellite transmitters that are used to track the movements of much larger bird species; this technology cannot currently be scaled-down to a small songbird such as the golden-wing, which weighs approximately 9 grams (0.3 ounces). The challenge with geolocators is that the birds carrying them must be caught again in order for researchers to retrieve the devices and download the data for analysis. They work well for a species, like the Golden-winged Warbler with high fidelity to their breeding sites; these birds have a good probability of being re-caught in the vicinity of where they were outfitted with the units last year (that is if they survive winter and the perils of migration). Just this past Saturday May 7, three birds with geolocators were observed in the exact same locations as where the units were deployed in 2015. Two of the birds were recaptured, allowing retrieval of the geolocators. After some data analysis, we will know where in Central or South America these birds spent their winter months!
Over the past 10 years, DGIF has funded and collaborated on various Virginia projects aimed at better understanding the distribution and ecology of Golden-winged Warblers in western Virginia. We currently lead a Virginia partners group working to further conservation of this declining species and to promote incentive programs for landowners to create and maintain quality habitat on their lands for the benefit of golden-wings and a host of other species. To learn more more about the Golden-winged Warbler and the work that has been done to date in Virginia, please visit our Golden-winged Warbler webpage.