One of my 4 hens is lurching to the side and can't stand up for very long. She started walking crooked 3 days ago. I noticed that she had her head cocked to her right and seemed "heavy", like she was leaning that way as she walked. The next day was worse with stumbeling. Today she's still alive, tried to walk, but collapsed after a minute or two, still with her head, neck and body seeming to be weighted down on the right side. She layed an egg all three days. I know she'll be dead today. I can't figure out what might have happened?!!! The chickens are in a small yard, all the others are fine. She is only one year old. Has anyone seen these symptoms/behaviours before?