Really nice exposure control on the white & black.
All that green seems to have caused a bit of color cast that carries over into the black. It goes beyond the refraction from the feathers I think.
There also looks to be a little bit of halo about center in front of the breast.
Although I'm not a big fan of perching birds in the ground, I could live with this one. Great use of depth of field and good separation of the eye from the mask, the image could go a tad lighter in my opinion and the bird is placed nicely in the frame. Shame the feet are covered.
Magpies don't seem to be posted at many forums but I do like to see them. I might have cropped this just a little tighter. I'd also echo the comments from Fabs and Robert about the brightness. It would bring out the blue on the wing a bit more if the image were lighter.