Wildlife Gardening: Does anyone know this bird?, 0 by Shelly221

Shelly221 wrote:
Sorry about the quality of the picture. It was taken at high mag. without a tripod LOL. I lightened the picture a little so the dark tail can be seen, and also the line from its eye to beak.
These little (I would guess 4-5 inches sitting, and a wingspan maybe 6-8 inches) birds flit around, hover, and make quick chirping noises. Their bellies are yellow. This is the 1st year I have seen or heard them here. I did a seach for yellow bellied (and buff belly) bird in Colorado, but nothing that I got to looked like these little guys. Any help would be appreciated.