Evolution works with what's at hand. So if you start with a normal bird skull – bill pointing forward, eyes oriented front or sideways, ears behind eyes – and introduce the challenge of seeing behind your head while your bill is pushed deeply into the soil, what do you get?
The American Woodcock answers this question. With its long bill constantly probing the soil for earthworms, its whole skull has been rearranged. Relative to other birds, woodcocks' eyes have moved toward the top and rear of the skull, pushing the ear openings downward. Apparently the brain followed suit!