Nest-boxes that have low entrances or offer owlets easy access to a ledge can be deadly.
Like all young birds, a developing owlet will be comparatively heavy-bodied - dense - like a squab. A fall from any sort of height could easily result in serious, if not fatal, injuries.
Barn owls must be sufficiently developed before they fledge. Ideally, they should lose most of their 'baby-weight' and have fully feathered wings so that when they take their first flight... or fall... they will not drop like a cannonball, but flutter to the ground - or maybe even fly.
Another flaw we see in nest-box designs is a perch. Perches allow predators, like great horned owls, easy access.
Our latest nest-box design was inspired by the Carolina Raptor Center. They are spacious, allowing owlets room to grow and move around. Most importantly though, the entrance is high off the floor - helping ensure owlets are well-developed before they fledge.
Please see more at our barn owl nest-box web page HERE.