Clicking during breathing is something that is talked about in many posts here if you do a search at the top of the page. I have only seen it in my chick with the injured air sac, but it could happen with other respiratory problems, or perhaps with a heart problem. It would be nice if more vets would respond to these posts to help us figure out why the clicking occurs. The leaking air sac I found was hard to miss, sincerely it covered the whole right side of my chick. I wouldn't be too concerned about the cclicking as long as she is acting normally.