I had one girl that had a poop cluster on her bum this last summer. Once it gets started, the poop catches more poop, and it just keeps growing. I was going to take her off the roost one night to give her a bath, and that plan had to be rescheduled by a small emergency. The next day I found the...
https://the-chicken-chick.com/whats-scoop-on-chicken-poop-digestive/
This is a post from a chicken blog that discusses chicken poop, in all its variations. It has lots of pictures (:sick ), so you can see what looks normal and what indicates the chicken may have a health issue. I found it very...