I'm not an anatomy expert, but...
*The shoulders seem awkwardly places, one is higher while the other is lower.
*From the looks it it, if I were to turn her around, she'd be missing her shoulder blades.
*This could be an artistic thing, but the feathers on her neck blend her shoulders into her neck too much...if that makes sense.
As for the shading, that's not necessarily my best subject, I'll leave that to the better artists here.
*Edit*
Couldn't help myself
Sloppy edit of what I meant.