I've got a weird one for you all today. I've already figured it out, I'm just leaving an account here so that if somebody experiences something similar in the future they will be able to find a probable cause during their internet searching. This bird initially presented with minor diarrhea - kind of dribbly - that was building up on the feathers below her vent. I brought her in to give her a bath, dried her off, and then put her up on the closet door so I could keep an eye on her and so she could completely dry (a big deal when it's -20F outside). About 10 minutes later she jumped off the closet door onto the floor (about 7 feet below) - and here's where it gets really weird! She walked a few feet and then started puking up crystal clear water. No joke! This went on for about a minute, after which she drowned. Below is a picture of the bird plus water. That's a helluva lot of water to come out of a buff orpington! I did the necropsy myself, and the results are rather unsurprising in retrospect. The bird had egg yolk periontitis, which had caused an internal infection. The infection resulted in fluid buildup in the abdominal cavity. When she hit the floor the pressure combined with the shock ruptured her upper digestive tract (above the intestines) and the water was forced out of her by the pressure of the abdominal walls on the fluid. A very curious case, but now that I know what caused the problem I am grateful she drowned. Much faster than death by internal infection.