Very dramatic BG and great light. I agree with Tony about the dark areas of the plumage and I like the composition. The bird´s pose is very interesting.
Dramatic. Like it. You are absolutely correct about the light. It looks as though it was overcast because there is an even diffuse look, and there is not any evidence of contra-shading.
If you mask the wing area and then promote the masked area to a layer, you can use an adjustment layer to tease out the details: then blend with the underlying layer to get the effect you desire. Good image.