Flawless rendering. You managed to capture the soft quality and texture of the feathers, matched quite nicely by the "snowy" effect you created. Though there seems to be an uneven tonal region in the background that seems to border the hawk a little. Kinda makes him look like he's glowing. Maybe that's intentional. It just caught my eye, is all. Love the piece.
Very good tonality; crisp, excellent sense of form to the head and beautifully rendered eyes. The feathers add to the sense of twisting as it turns its' head to see use. It's a very lifelike drawing. Great job.