help with roosters neck?

o.k my boy has a patch of feathers missing on his neck and it is realy red, i noticed it last week, now today its even bigger and real red and i see it was bleeding!!!? i only have 4 hens and 1 rooster in a 8x8 coop and a run outside wich they are aloud all times except when its -40 now is this plucking? what can i do to save their feathers? and stop them from doing this, i hung a cabbage and they havent touched it??? also 2 of my girls have bare/red bums..i realy dont like them doing this or is it something else?? HELP! i keep their coop very clean with fresh shavings , they get table scraps...i dont like my birds to look like this...

My guess is he reached through the fence to eat something and made a sore, then the hens pecked at it.
Not sure what you can do except seperate them until it heals.

If the hens are howing similar signs it could very well be a parasite (louse), try Vaseline applied liberally to affected areas.

My vote is for rug burn from the girls backs. He may not have minded his injury!