Check out that high ISO performance! Quite sharp with that focal lenght and shutter speed. I bit of a better head turn and a bit less room above would have made this even better.
The orange legs instantly eliminate this from being Blackburnian Warbler - Blackburnians have black legs and feet. This, combined with the whitish face (female Blackburnian has yellow wash) and black broken streaking on throat and chest would suggest female Blackpoll Warbler.
Amazing sharpness at 1/50, Joe. I agree about the clean perch and nice background. On my monitor, the greens in the background have a slight bluish cast. I think the image would be more appealing overall if you warmed up the color balance just a bit.
Thanks for the tips, re: color temperature. I believe it was set to AWB, which rendered 5200k in CS4, but it definitely does look like a "sea foam green" when I take a look back at it.
Only got a quick handful of shots before it was gone...Wish I had more head positioning opportunities!!