Bushtits are tough to photograph; they never seem to sit still, and they're rarely on a nice clean perch. I'd like to see a slight head turn to the left of the frame. The bird is not looking right at you, nor is it giving us a nice profile. I would also clone out the light spots in the area between the body and tail.
I don't know how much you cropped this, but I feel it's bottom heavy. I'd loosen it up all the way around. kind of a tough perch to make look good, but since it's what the bird chose, I'd include more of it for balance.