Burke graduate student Meade Krosby and curator Sievert Rohwer investigated the genetics of two northwest forest bird species – Hermit Warblers (Dendroica occidentalis) and Townsend's Warblers (Dendroica townsendi). The geographic ranges of these two warblers overlap in what is known as a "hybrid zone", in which two species interbreed and produce offspring. Meade's genetic analysis of these species indicates that Townsend's Warblers have been slowly displacing Hermit Warblers over much of their original range, leaving a genetic signature called a "wake": traces of Hermit Warbler genes are found in birds that otherwise look like pure Townsend's Warblers. This is consistent with earlier behavioral studies that found Townsend's warblers to be more aggressive competitors than Hermit Warblers.
For this project, Meade analyzed DNA from 226 warblers from 22 locations. All tissues are archived in the Burke's GRC.
Krosby, M., and S. Rohwer. 2009. A 2000 km genetic wake yields evidence for northern glacial refugia and hybrid zone movement in a pair of songbirds. Proceedings of the Royal Society B: Biological Sciences, 276:615-621.