About 8 months ago, we obtained 6 'mountain hens' from a friend. He had no idea how old they were, as they were roaming his property and he wanted to find them homes. Yesterday morning, one of the hens was standing on one leg by the coop and didn't run away when I went into the enclosure to feed. This was unusual, because they are afraid of us and won't come near us. I picked her up, (also unusual as we could never get close enough to touch any of them previously), and she didn't appear to have a broken leg or wing and didn't seem to be distressed. When I went back to check her in the afternoon, she was dead. We recently changed the feed from crumble to a mix of pellets and scratch. Could that have done it? We know this hen was no longer laying, so could it have been old age?