The basic answer is rodents, the specific rodents depends on the region. Their favorite meals include voles, pocket gophers, moles, rats, mice, small snakes as well as some insects that are active at night. Barn owls are nocturnal hunters primarily one hour after sunset and ending one hour before sunrise. If food is scarce, you can see them hunting during the day. Remember that barn owls weigh 1 to 1 1/2 pounds full grown and they eat their prey WHOLE. Your dogs, cats and chickens are safe. If you leave kittens, puppies and chicks outside at night unprotected that’s on you!  There are many predators hunting at night that do eat the aforementioned including great horned owls, coyotes, fox, bob cats and others depending on where you live.  One barn owl will typically consume 2-3 rodents a night, which works out to approximately 1000 rodents year!