Designed for Darkness: The Unique Physiology and Anatomy of Owls

Abstract

Owls are the only truly nocturnal avian raptors and have evolved several unique adaptations to perfectly fill this role. For example, their unique large tubular eyes, packed with light-sensitive cells, enable owls to operate in almost total darkness, while their remarkable auditory system allows them to operate in complete darkness. This unique and complex auditory system is a combination of specialised feathers forming a parabolic facial disc, adjustable operculum, or flaps and, in some species, asymmetrical ear openings. This unique system allows the owl’s brain to construct an auditory map of space when locating its prey. As remarkable as it seems, this is tantamount to owls being able to hear in 3D. While there are minor variations in the individual physiology between certain species due to the type of prey they take and the habitat they operate in, all owls are subject to the same unique adaptations in eyes, hearing, head rotation, feather structure, digestive system, and hind limb musculature. In this study, we examine each individual adaptation that combines to make the owl a superbly designed nocturnal predator and also look at some shared mechanisms and behaviour patterns that are crucial to its survival.