I "yard" my birds. They wander the yard at day, and they go up to the top of the coop to roost and sleep at night and I shut them in until the morning. Last night I got home a bit late and it was already dark. All of my birds were up at the usual spots in the coop. But one of my birds was at the bottom of the coop, at the dry part. It was just laying there breathing. I decided to move it up top since it gets cold at night but it was at a part that was difficult to reach so I used a branch (feel bad about this now). Bird was being stubborn about moving and I had difficulty moving it to where I could grab it out of the coop. Bird seemed lethargic and I noticed some discharge near (not on) the vent (greenish, yellow, thick). But it was breathing (maybe a bit heavy). I put it up top with the birds so it would stay dry and warm. The next morning I let the birds out and they all left the coop per their usual behavior. But the sick bird was just laying there in the muck on the uncovered (wet and mucky side) of the coop). I removed it from the muck and put it outside the coop. It just laid there and the other birds started picking at it. I decided to isolate the bird. I brought out a brooding box, put some dry bedding in it and brought the bird into the garage. I put a heating light there to try to keep it in the high 70s low 80s. I dried off the bird and wiped off the muck. I put food and water in the box and left the top off. Bird was really lethargic, its head was slowly spinning around (kinda like it was nodding off) and it had difficulty keeping it up. Then it just started drooping its head. While I was eating breakfast I heard "thrashing." I went to check on the bird and it was lying on its side but still breathing. But by the time I ate breakfast and got ready for work the bird was dead. Any ideas on what killed it? What can I do to keep the other birds from getting sick. It's been raining everyday around here and been pretty cold as well. I've kept the top of the coop where they roost, clean, dry, and full of fresh bedding. Uncovered bottom (and most of my yard) is pretty much wet muck. Not much I can do about that until it stops raining every day.