This video from the USA says about itself:
Barn Owl Attacks Snake Entering Nest Box. May 6, 2015
From the Cornell Lab of Ornithology in the USA about this:
Earlier this month, we witnessed a reminder that the Texas Barn Owls aren’t the only ones hunting for food during the night. Despite extensive predator guards installed around the owls’ box, a Texas rat snake gained access to the rafters. Our cameras captured the ensuing showdown as the snake approached the nest box entrance. Despite the midnight darkness, Dottie (the female owl) evicted the snake from the box, then, moments later, gathered her nestlings back to safety beneath her. Watch video [above].
It’s not just other predators that make raising a family of Barn Owls tough. The breeding ecology of Barn Owls can be boom-or-bust. They can be prolific breeders, often laying six or more eggs during a single breeding attempt, but if there’s not enough prey to support all of the nestlings, many can perish. One 16-year study in Utah found that, on average, only 63 percent of eggs hatched and 87 percent of hatchlings survived to fledging. This year, only 5 of 6 eggs hatched in the Texas Barn Owl nest and the youngest owlet (hatched nearly 11 days after the oldest) did not survive. The four remaining owlets appear healthy and well, and we are hopeful that they will survive to fledge. Watch cam.