If you have a rooster with spurs, it could be spur wounds. A spur wound occurs when the rooster's spur catches on the hens skin and yanks, ripping a hole in the hen's side. You can buy Vetericyn and Sliver Sulfadiazine cream to put on the wound to promote healing and prevent infection. It could also have been a hawk or other predator. It is probably best to seperate her from the rest of the chickens in a run inside the pen so they can see her and she can be outside. You can trim your roosters spurs and wrap them in duct tape to make sure this doesn't happen again. Be careful when trimming because they can bleed if you trim too much off. If they bleed, pack cornstarch into the spur and watch him until it stops bleeding. If the hen seems droopy or isn't eating or drinking, the cut has probably become infected and she may have a fever. You should bring her to the vet in this case. Hope this helps!
