Anyone who regularly reads our newsletter, blog, or attends our programs knows that Audubon North Carolina has spent a lot of time and effort over the last few years working to learn about and conserve Golden-winged Warblers (GWWA). And we are not alone. The Golden-winged Warbler Working Group (GWWAWG)was established in 2005, by more than 75 partners, to dig deep into the science and life cycle of this species. In this series of blog posts, learn about all the work of the GWWWG and what this collaborative effort has done to protect this tiny gem of our forests.
Post by Curtis Smalling, Coordinator NC IBA Program & Mountain Program Manager
We partnered with John Gerwin at the NC Museum of Natural Sciences and Sharna Tolfree, a graduate student at the University of North Carolina at Wilmington, to see what was going on in Nicaragua. Richard Chandler in Costa Rica completed the first work on this topic; we followed his lead for our study by putting transmitters on several birds. Sharna tracked their movements.
What we found showed that they defended forest adjacent to openings like shade coffee and shrubby fields, but tended not to defend the early successional from other Golden-wings. Their territories often overlapped in the early successional meaning they made use of those habitats, but really defended their forest from each other. Females overlapped with males and tended to be associated with a particular male, but more study is needed to tease out those relationships.
And of course, we all want to know if those pairs are the same birds that will settle in a field in North Carolina to breed next summer! We are just beginning to understand where specific populations may be wintering. They do have what we call site fidelity with the same bird returning to a specific area year after year. One female Golden-winged at our study site in Nicaragua has returned for at least four years!
Given the importance of forest at these points in the breeding life cycle, it made us start to look at our assumptions about the habitat they use and prefer on their wintering grounds. We had helped with wintering range surveys a few years back, and one of the things that stood out was that we found birds up to 30 meters into the mature forest, usually around wet areas or tree fall gaps where there was more dense vegetation, especially the vine tangles and bunches of dead leaves hanging in them that they seem to prefer for foraging. We also knew that they did use habitats that looked like what we thought of as breeding habitat - shrubby fields and edges. But most of us assumed that they used mature forest more than they do on the breeding grounds.
The telemetry work of the breeding grounds made us realize that they probably use these different habitats in much the same way, especially given that on the wintering grounds they aren’t pulled as much into early successional to nest. Forest remains an important component for their wintering grounds, and the transition to edge (the transition area between two types of habitat) seemed important as well.