When Merlin passes one of her huge ones from a combination of hormones (huge ovary) and the Bornavirus she can fart quite loudly, and sometimes there is a smell also. But, it helps me know she did it and then I can go clean it up before she steps in it since I have no grate in her cage. I have also heard Rowdy do it a few times lately or she is imitating the sound of one (including in her sleep).
If you see bubbles in the poop that is a sign of gas. Now birds have a very short digestive track so you aren't supposed to hear audible passing of gas, but it's been going on here lately! In 43 years of bird ownership though, it's never happened before. Merlin is a special case though. If you saw what comes out of her sometimes you would understand why she has a gas backup. Poor girl; yesterday it just didn't want to come out and I had to keep getting her out and making her move around until it finally did. Thankfully it landed on the protective cover I put over my lap. She gets another hormone shot this morning so that should help.
