i have had two birds attacked by hawks this year so far,both have managed to get home with horrific injuries.i have found that a pigeon has amazing healing capabilities and is best left alone to tend his own wounds.as long as there is no bleeding all you have to do is keep a close eye on the bird,if he,s really badly wounded put him on his own in a basket but near to the other birds to make him feel safe and calm.you will be amazed at how quickly they recover.its up to you whether or not you give antibiotics but unless a infection is evident i would not bother.give him some time and he will be fine,please,please do not kill just because he has a bit of bad luck.