Yes, they can poop during their death convulsions because of all their muscles contract so strongly. I usually do fast my birds for 12 hours prior but its not a steadfast rule for one that needs to be emergency butchered.
Okay! I'm sure that was a dumb question I thought to myself well of course they would wouldn't you? Lol I had just done a few a couple of weeks ago with no pooping and these did so it kinda threw me off which neither set had fasted before hand but from now on they will be fasting before getting butchered because that just wasn't pleasant! Thank you for the help!
This site is for learning and most of us are more than happy to help. I prefer fasting them, just for the reason that it is more sanitary. My birds free range so they still have access to grass but at least that doesn't pass through them like their crumble feed.