Blue-winged Warbler singing Golden-winged like song

Blue winged Warbler, Quabbin, May 21, 2011 (heavily cropped)

During a breeding bird atlas trip this morning to the restricted Prescott Peninsula I came across this Blue-winged Warbler singing a very Golden-winged like song. The bird appeared to be a 'pure' looking Blue-winged but I certainly would not be surprised if there is a lot in the way of genetic material from a Golden winged in the bird. I ran across a similar type bird several years ago in Northampton but it also visually appeared to be a Blue-winged Warbler. I got audio and video but cannot seem to load it up here. I will try again with it later.