I opened the image in ACR and made some corrections to reduce noise, reduce CA and add vignette. Then opened as a smart object.
I made a duplicate smart object layer via copy and returned to ACR to sharpen the eagle.
A selection was made of the sky (using the magic wand tool) and inverted for a layer mask on the duplicate layer. This reveals the sharp eagle. I refined the edge of the mask and touched up a couple of masking spots that needed additional attention.
This may not be as good as other methods, but it was a new idea to me that is pretty simple and easily editable by returning to ACR with the smart object layers.
A curves adjustment layer is clipped to the eagle layer to adjust contrast.

forum discussion: http://forums.dpreview.com/forums/read.asp?forum=1006&message=38530843&changemode=1
original image by JTAnFIA: