How old is your birdie? If its still a chick, take a damp, warm paper towel and clean the ick off of his booty. If its an older bird, give it a quick bath to remove the build up. Poo left stuck to feathers can lead to ammonia burn, which isn't fun for anyone. Good luck!
He's about a one year old rooster. An Amerucana, rumpless and it seems like since he's got that weird tail-less butt that he's prone to a messy rear! Just wondering if this is common in rumpless birds?