the crop is a sac near the bottom the neck, on top of the breast, slightly to the hen's right.
at roost time, after they have been eating all day..
the crop should feel full.
in the morning before they eat, it should feel empty or flat..sort of like an empty balloon.
check for any lumps or grainy feeling..or any sour odor from the mouth..
when was the last time she ate?
don't pick up the hen to listen to breath sounds..
just act normal..and listen..
when did she last lay an egg?
do her eyes look wet, mucusy or bubbly?
any drainage from beak?
what all do you feed?
how long has she been sick?