[AnnieK]

If it's a baby, I would imagine it will have fallen from the nest so doubt its the dog's fault. To be fair, if you can humanely end its suffering, that will be fairest.

Edit: just seen the pic and it would appear to be older than I was imagining as it has flight feathers. I would leave it and let nature take its course....if its just stunned it will fly off when its had a rest