We have many varieties of owls here, but never had a problem with them among my hens ....although if they are feeding chicks, then maybe. To be honest, hens that size I would not think they would touch. Last year we kept losing our half grown chicks, and one day found a young buzzard in the lane, having fallen out of a tree. We then realised the mother had been taking the chicks for her young - easy pickings!! The little Buzzard we took to the owl sanctuary up the road, for them to care for.