On Monday the 18th of May, I visited this site to download the latest video files. I scrolled through the videos to make sure that the system was still working and to my surprise, a male Barn Owl appeared in five videos! He entered the nest box on the 17th May at 03:51 hours. It’s a tight squeeze for a Barn Owl as this box has been designed for Little Owls; it has a narrow entrance hole and corridor. He must have heaved through the entrance hole and dragged himself along the narrow corridor, flat on his sternum, before entering the nesting chamber. This female Little Owl was in the box's nesting chamber and she was incubating her four eggs; she's been incubating these eggs for 27 days so far. The male Little Owl was away from the nest site and was probably hunting.
The female Little Owl engaged in a territorial fight with the Barn Owl. It's remarkable how well this Little Owl defended her nest; she's half the size of a Barn Owl! Barn Owls have a superb sense of hearing so it's likely that he knew that Little Owls were breeding in this box. Why did this Barn Owl enter the nest box?
Was he looking for a nest site? Some Barn Owls haven't started breeding yet, which is later than in an average year, and may still be looking for a nest site. In 2014, a third of pairs had a second brood, which is energetically demanding, plus Field Voles, their main prey, appear to be less abundant in 2015. This means that some females have not yet reached their breeding weight. Barn Owls are known to predate Little Owls. Perhaps by disturbing this Little Owl, the Barn Owl was hoping that she would abandon her nesting attempt in response to his threat of predation. He could take over the box if she abandons her eggs.
Was he looking for a roost site? A male Barn Owl will often roost in a separate cavity to the female of a pair. There are several pairs breeding nearby - could this be a male of one of these pairs? We recorded a Barn Owl roosting in a nest box of this design in 2009. There are vacant Barn Owl boxes nearby.
Barn Owls and Little Owls both eat small mammals; they form the majority of the Barn Owl's diet, whilst Little Owls eat other prey, such as worms, beetles and moths. If this Little Owl abandons her eggs there will be less competition for food from her chicks. Maybe he was hoping there would be chicks to eat.
The big question is will the Barn Owl be back? I think he probably will be. You can watch this encounter below and please revisit our blog for the latest update.
This Little Owl heard the Barn Owl enter the box as she stopped incubating her eggs a minute beforehand. At 03:51 hours, the Barn Owl heaved himself into the nesting chamber, and glanced at the Little Owl. Initially, she was standing at the back of the box under the camera, then furiously lunged towards him three times; she was defending her nest site and eggs. After 25 seconds, this Little Owl once again retreated to the back of the box and the two owls continued to look at each other for a minute.The Barn Owl glanced at her eggs, prompting the Little Owl to lunge at him two more times. He then heaved himself out of the nest box after an initial hesitation - maybe the male Little Owl was in the box corridor? The female Little Owl resumed egg incubation a minute after the Barn Owl had left the box.