Others had the same results when reporting mouse chewings....some birds had it but not all. Seems like the birds that roosted lower(lower on the pecking order) were more likely to have it and it's never the rooster showing up with chewed feathers~presumably because he's the highest in the pecking order, thus roosting further from the floor of the coop. I don't ever have ladder roosts, so a mouse would have to crawl a vertical surface to ever reach mine and I usually have linear roosts so most birds are roosting at the same level.
I ordered from McMurray, and got 12 Cornish X, 6 Pioneer, 6 Red Ranger, 2 Dark Cornish and 2 Speckled Sussex, and they threw in a free "rare breed," which we think is a Brahma. All of the deaths were out of the blue. One of the Cornish X died a few days in, then a few days later one of the Pioneer, then yesterday a Dark Cornish.. 
