We free range. We don't have problems with owls yet but have had issues with hawks trying to catch our hens. We had a friend that had Silkies. She didn't lock them up at night until owls started to attack them at night. They use to peck their heads open. I know, yuck and very sad. She lost about 5 chickens that way until she made sure they were secure at night. Sounds like the owl is checking out your chicks. I think that the mobile wire covered box is a good idea. I wouldn't leave small chicks/young hens unsupervised outside if I were you.