Now, in addition to what happened here https://www.backyardchickens.com/forum/viewtopic.php?id=567094 we have a chick completely gone. The young are in a separate coop type enclosure, made of heavy plywood sides, wood and wire floor, and a metal roof. The older birds are down below, on the ground, enclosed with wire. The ones that have died were in a completely different pen about 15 feet away. No rat trouble with this pen. We have had a rat problem, with eggs disappearing, from the big pen in question now but never had anyone to disappear from the top without a trace. We have looked, and can't find anyholes or breaches. The only thing I can think of is at the very top, maybe a 1 or 2 inch space ahere the roof meets the wood frame. Could something get in and back out without causing a ruckus? We have heard no new noises at night.