Found an injured seagull is there anything I can do for it?

I found an injured seagull near my house in a field. His wing appears to be badly broken. I went back and gave him a small piece of bread and a container of water. My mom says he will probably be killed tonight by some wild animal, is there any way I can prevent that from happening? Like put a cardboard box with breathing holes over top of him? Or would that not work..thanks for the help.