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
Recent work is also hinting that this forest-cover factor may be very important in keeping the closely related Blue-winged Warbler at low densities where Golden-winged Warblers occur. These two species are very closely related, in the same genus (Vermivora), and the only two remaining species in this genus. Where they occur together, they hybridize, creating some standard hybrid phenotypes. (A phenotype is the outward appearance of an animal that is consistent, like a gray phase or red phase Screech Owl)
For Golden-winged Warblers, these are Brewster’s Warblers and the more rare Lawrence’s Warbler. Bird hybrids are usually fertile (unlike what you have heard about most mammal hybrids), and readily backcross with either of the parent species. Usually, whatever species phenotype is more common on the
landscape then starts to mask that hybrid history after successive generations. For example, a Brewster’s Warbler surrounded by Golden-winged phenotypes is more likely to breed with a Golden-winged Warbler, and their offspring will start to look like Golden-winged Warblers again. But the hybrid genes are still in the bird’s genetic makeup. Birds that look like one of the parent species but have some of the other species DNA are known as “introgressed” individuals.
We captured birds, took blood and feather samples, and analyzed those for these hybrid markers. Rachel Vallender pioneered this work while at Cornell, and thanks to her methods, we now know that about 10% of our birds here in North Carolina have some Blue-winged Warbler ancestry in their history. So maintaining a higher percentage of forest cover to discourage Blue-winged Warbler colonization may be an important strategy to maintain the species.
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 [link to tag], 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
Much work is still going on in an effort to understand this interaction. Here in the Southern Appalachians we have another tool in our kit to discourage Blue-winged warblers and encourage Golden-wings, the elevation of the mountains themselves. Golden-wings typically occur above 3,000-foot elevation, whereas Blue-winged Warblers in N.C. typically occur beneath 2,500 feet. There are exceptions, but that elevation preference helps keep the two populations somewhat segregated, insuring that backcrossing of any hybrids trends toward Golden-wings at higher elevations and Blue-wings at lower elevations. We think this is why in some areas of their range (like lower elevations in Pennsylvania), Blue-wings have rapidly replaced Golden-wings in where both can occur together easily, and where forest fragmentation is a big issue.
In our next entry in this series, learn how telemetry helped solve where GWWAs go after their morning foraging. Read the full series here.
