Could be that. They don't need a very large space to crawl through, though, to get into your coop. I'm guessing the rat killed your chickens. Many years ago,I had a small coop that sat directly on the ground. One winter I couldn't figure out why the feed consumption was so high and egg production was so low. I was using the deep litter method (although at the time I didn't know it even had a name) of bedding, so I didn't clean out my coop until spring. When I did finally clean it out, the floor had multiple holes chewed through it, and I could see the little buggers moving around down there! They even had the nerve to pop up and look at me! For a few minutes, it was almost like playing "Bop 'Em Gopher" at the arcade. (I lost) We got the rats eradicated, and my coops will forever be elevated on cement blocks to prevent anything from hiding under them ever again.
When an owl takes to the wing I have never been able to hear it and I have had GHO fly off while literally inches away from my ears. Silence is how owls make their living.
