Owls’ stealth stems from feathers that fly in silence
An owl’s greatest weapon is its feathers. Strong, sharp talons are good, and pointed, flesh-tearing beaks are nice, but they’re nothing if you can’t catch your intended prey. Since nocturnal owls hunt animals that are accustomed to relying on their ears more than their eyes in the dark, they’ve evolved to stay one step ahead of their prey by flying very quietly. So while other predatory birds may simply outrace their meals, owls catch their dinner on soft, silent wings.
An owl’s feathers contribute to its stealth in a variety of ways. Depending on where the feather is located, it can play a different role in dampening the sound that a wing makes as it pushes against the air. So in contrast to a fast bird with smooth, taught feathers built to achieve speed, an owl’s plumage is specialized to cut down on even a hint of flapping. This starts with the leading edge of each wing, which is lined with a row of curled, hook-like structures that break up the air before the wing moves through it. So rather than a large, focused sound, the air is broken up in to “micro-turbulences,” which are harder to hear. This effect is then replicated on the back of the wings, which end in slightly fringed-looking feathers, again to break up the air rather than slap against it.
While the flight feathers are obviously important, the body feathers play a role as well. Owl feathers are notably soft and fluffy, covering the bird’s legs down to its feet. Aside from providing insulation, these feathers also absorb and dampen sound from the wings. This dampening effect is especially effective against higher-frequency sounds that just happen to be what most prey, like mice or rabbits, are tuned into when gauging their surroundings.
No hurry when you can’t be heard
Finally, the movement of the owl’s flight helps minimize noise as well, if at the cost of speed. The fastest great horned owls only reach speeds of 40 miles-per-hour, slower than even a mallard duck’s top speed of 65 miles-per-hour. However, the owl’s large wings are good at generating lift without a lot of flapping. This allows the bird to sail over the ground with minimal activity, and thus minimal noise generation. As long as the owl remains undetected by its target, moving slowly isn’t the huge drawback that a daytime predator needs to worry about.
Source: Wing Feathers Enable Near-Silent Flight: Owl by Ashley Meyers, Ask Nature