Chickens CAN hold it, its just some are more clean conscious than others. I imagine just like people. I have a little hen I could totally housetrain. She never ever pooed on us, ever, and we used to hold her a lot. She would squirm if she needed down to go poo. She hates stepping in it. She wont poo if I have her in my bed with me either. She just somehow "knows". She is a showgirl and also goes broody often. Never ever poos on the eggs. She will come off once every two or three days and do a huge horse poo.
She had a little D'uccle share her nest one time and she got SO MAD, cuz the D'Uccle will go where and when she has to pretty much. She finally chased her out of the nest when there was one time too many 'accidents'.
She also learns. I have had two chickens I could housetrain if I chose to. Now the others, I must admit, no amount of training would make them hold their poo, or train.
It helps if they are very poo conscious. The two I had totally hated stepping in it, or having it where they had to step in it. One EE hen I had even kept and taught the other from pooping in the little mini desk coop I had set up for them. It was amazing. I even took pictures when I went to clean it out a month later, not one poop in it.
She had a little D'uccle share her nest one time and she got SO MAD, cuz the D'Uccle will go where and when she has to pretty much. She finally chased her out of the nest when there was one time too many 'accidents'.

She also learns. I have had two chickens I could housetrain if I chose to. Now the others, I must admit, no amount of training would make them hold their poo, or train.
It helps if they are very poo conscious. The two I had totally hated stepping in it, or having it where they had to step in it. One EE hen I had even kept and taught the other from pooping in the little mini desk coop I had set up for them. It was amazing. I even took pictures when I went to clean it out a month later, not one poop in it.