Air sac in chick's shoulders?

[ChocolateMouse]

I have 13 CX chicks a week old today, and they seem to have some sort of issue going on. When they settle down to relax, they tilt sideways. I looked one over and found what looks like an air sac between it's crop and wing on one side, not the other. A few of the chicks seem to have this. What is this!?

 

[Farmer Viola]

Are you sure it's not the crop itself you're feeling? They fill their crops with food, and it can look quite silly when full, and it will feel soft to the touch.

 

[ChocolateMouse]

I am pretty sure... It's not centered and it transparent and looks like air or fluid... I guess it could be. The chicks are otherwise healthy (save for tipping over sideways when they settle down) so maybe I am freaking out over nothing. But we did have on chick die on us, unable to walk or sit straight, half the size of the other 13 chicks... And it's my first time with baby birds.

Also it appears to be between the crop and the wing, near the shoulder.

 

[AbbyTravers]

I don't know but I have a chicken about 3-4 months old that is having that bubble. I hope its nothing though.