Good self-critique on needing more DOF, I agree. I certainly understand that the bird is dynamic making it hard to frame it. Work looser in framing so you do not clip off parts of the bird, like the toes in this case.
The 50D at ISO 800 will have luminance noise in the BG so I recommend noise reduction there.
Sharp on the eye where it counts and the diagonal perch adds a strong compositional element to the image,
Beautiful bird that I've never seen before. Agree with comments above.
Given what looks like a quite angled tail position, don't know if you could have shut down enough to get it sharp.
Muy buena toma aunque el corte de los dedos me haga sufrir un poco!
I agree about this birds being very active, you don't include information about if flash use used, I will assumed it was not. Flash as you know could provide you with faster shutter speeds.
This species looks a lot like our Rufous-capped Warbler,Basileuterus rufifrons, which can be found at middle elevations.
Nice to see you posting here. Good place to learn a lot.
Agree with the critics above. Nice to see a nice Mexican bird and hope you can get it again with better light conditions.
Lorant