Flight and Feathers
Most owls share an innate ability to fly almost silently and also more slowly in comparison to other birds of prey. Most owls live a mainly nocturnal lifestyle and being able to fly without making any noise gives them a strong advantage over their prey that are listening for the slightest sound in the night. A silent, slow flight is not as necessary for diurnal and crepuscular owls given that prey can usually see an owl approaching. While the morphological and biological mechanisms of this silent flight are more or less unknown, the structure of the feather has been heavily studied and accredited to a large portion of why they have this ability. Owls’ feathers are generally larger than the average birds’ feathers, have fewer radiates, longer pennulum, and achieve smooth edges with different rachis structures. Serrated edges along the owl’s remiges bring the flapping of the wing down to a nearly silent mechanism. Research has shown that the serrations are more likely reducing aerodynamic disturbances, rather than simply reducing noise. The surface of the flight feathers is covered with a velvety structure that absorbs the sound of the wing moving. These unique structures reduce noise frequencies above 2 kHz, making the sound level emitted drop below the typical hearing spectrum of the owl’s usual prey and also within the owl’s own best hearing range. This optimizes the owl’s ability to silently fly in order to capture prey without the prey hearing the owl first as it flies in. It also allows the owl to monitor the sound output from its flight pattern.
The feather adaption that allows silent flight means that barn owl feathers are not waterproof. To retain the softness and silent flight, the barn owl cannot use the preen oil or powder dust that other species use for waterproofing. In wet weather, they cannot hunt and this may be disastrous during the breeding season. Barn owls are frequently found drowned in cattle drinking troughs, since they land to drink and bathe, but are unable to climb out. Owls can struggle to keep warm, because of their lack of waterproofing, so large numbers of downy feathers help them to retain body heat.
Created by Cornelis de Jong