If you find a stunned bird don't always assume they are dead if they are not moving. Use gloves and pick up them up gently, trying to keep them upright to help them breathe. Place them either in a paper bag or a box on a soft towel, still trying to keep them upright. Place them in a dark quiet room. When a bird is in the dark they will stay calm, this will help them to recover from a concussion. Do not give them water or food because this can kill them. Leave them in the dark for at least two hours and if you think he can fly this does not mean he is fully recovered. I was fortunate that this cardinal did bounce back after a few hours. I was so concerned about him when he was set free. We don't have any bird rehabilitation center nearby.
These smaller hawks will fly into areas filled with birds, especially at birdfeeders and scare them so that they will fly into windows or other objects which will stun them, making it an easier catch for the hawk. I was so upset about my cardinal bird that I called the Game and Wildlife Agency here to ask about caring for the bird, they couldn't help me much. I whined to them about my hawk and the man did confirm that the hawk can see colors and it will target these poor Red Cardinals since they show up so vividly especially now against the white snow and no leaves for cover.