The first time I heard it I was looking around, as if a squirrel was around eating a nut, or a tree limb cracking. It sounds like that- then I leaned in closer and it was coming from her! I couldn't believe it. I haven't heard it the last few days but I did a few days in a row last week, constantly. It was very loud, odd. I just cannot imagine it would be a respiratory infection- but I suppose it is possible. She has had a warm bill for a while now. She's had a bit of a difficult life. When I got her and her sister from McMurray, same age, a couple days old, her sister was pecking at her eyes in transit, so when she got here I had to treat them- so she can't see as well as the others. She seems a little more lethargic than the others but not a huge difference.