Yes, they are made so that there is a pocket under their vent to catch the poo which you put some sort of absorbent something in: a bit of sanitary pad, one of those makeup remover pads, whatever, depending on the size of the bird and the pocket.
I can't really say I've used one. I have one and have put it on a chicken but never really left it on very long. It freaks them at first and they squat and try to run backwards out of it. Since I was dealing with a 5 week old, I didn't push it. And she didn't poo in it either. Same experience with my cockatiel. I never pushed it with either of them.
I'd be interested to learn of anyone's experience with them too that has really used one.
I guess I was wondering how gross they were to clean, or if part of it was disposable. Seems like the poo
would get all over the inside. Also wondering if the chickens get used to it. My daughter would love to
let a chicken run around the house occasionally. But we have carpet. : )
I just got some from lovemychix for my ducks. They work wonderfully. The pouch part is lined. I put half a maxi pad in the bottom to catch any liquids and just dump the rest out in the trash. They rinse off nicely. I'm really happy with them.