If the bird was injured a few days ago, the bruise would appear green. They have different blood structure, and bruises turn green instead of purple like in people. Bruises are not contagious. If the bird died a few days ago, it would smell bad, and possibly have a green color on the down side due to the insides rotting and material leaking internally. So what you see may be the outcome of death or injury, but is it not a cause of the death...
