Apart from everything else about it, I particularly like the textures in this shot. Complemented by the somewhat ominous tones, which is appropriate - that is a bird of prey after all. The smaller birds really add to the perception of depth in this photo, which is sometimes surprisingly difficult I find in shots with a fore to background depth of field. Of course, the strong perspective lines of clouds, sun's rays and even the slight slope of the horizon all help. There's is a lot happening in this shot, and it all works a treat.