Ok, this is a bit bizarre, but a couple of days ago I went out to check for eggs, and one of the girls was on the nest, but had something dark and fluffy underneath her. When I looked closer, I found it was a dead blue tit. I can't quite work it out. The coop is next to my potting shed, and from time to time I get dead wild birds that have flown into the potting shed windows (thinking that they can see through to the other side, so they try to fly through, and break their necks). The thing is, the nesting box is inside the coop, which is inside an enclosed run next to the potting shed. I can't see a wild bird going inside a dark 3 foot long coop and then getting up enough speed to fly into the wall and break it's neck and fall into the nest box. Is it possible that one of the girls found the bird on the ground outside by the potting shed, and carried it into the nest box to keep warm, as if it was an injured chick? I only got my girls a few months ago, and none of them are broody (they've only just started laying), so I don't know if it would be possible or not. It's not a problem, I'm just extremely curious to know if it's a possible behaviour or not.