We have had chickens for a long time, and about a month ago one hen had an air bubble on her right shoulder. A few weeks later, she died. Last week i noticed that on one of my roosters he had the same air sack on the same shoulder. What is it? And how Can it be treated??? Also, yesterday, i saw on one of my baby chickens she had it too! I dont want them to die so can anyone give my some advice? Do your chickens have air sacks??