I noticed a runner duck hen not walking so brought her inside. I do not see anything wrong with her legs, no wounds, nothing of that sort. While examining her I can heard a sort of crackling/crunching sound coming from inside her... not out of her mouth, but from inside... if that makes sense. She does not seem to be with egg, though I could be wrong... she isn't large down below like I'm use to when they are with eggs. I have a call into the vet, but he hasn't called back yet. Is anyone familiar with this sound and know what causes it?