Reflected moonlight found to make barn owls less visible to prey

A team of biology and optics researchers affiliated with a host of institutions in Spain has found that the unique undercoating of the barn owl helps to make it less visible to prey when flying under the moon and starlit skies.

In their paper published in the Proceedings of the National Academy of Sciences, the group describes how they used a variety of techniques to assess light conditions at night and what a barn owl might look like to prey, such as rodents, as it swoops down to catch them.

Most owls, the researchers note, have a lot of color in their feathers, which helps them blend into their surroundings, making it easier to catch mice, rats and other prey. But the barn owl has a pure white underbelly, which would seem to make it easy for prey to detect. It also has a round white face.

The team wondered if the unique coloring helps the owl to blend in against a cloudless night sky. To find out, they conducted a study of light conditions at night, exploring how barn owls would look against them and what they likely would look like to prey.

The work by the team involved modeling how light played off the sky, various parts of the ground and the owl’s plumage. They found that the reflected moonlight made the owls barely visible to a creature situated on the ground. They also found that on nights when there were no clouds, the contrast between the owl’s white, reflective underside, which was very similar to that of the moon and the sky, was too low for most rodent prey to detect. And that allowed the owl to blend in with the background as it quickly and quietly swooped in on prey.

The research team concludes by suggesting their work showed that it is very likely that the white underside of the barn owl and its white round face make it difficult for prey, such as mice, to see the bird before it’s too late to make an escape. Thus, the unique coloring of the owl serves as effective camouflage.

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