One of my golden memories is sitting with my back against a tree on an early morning in late summer, the wheat had been cut and the mice could be heard scuttling around. I was waiting for a Roe buck to appear, as he always seemed to, across the field - which was only 100ish yard away. As the sun came up there was a Barn Owl flying a grind iron pattern over the field. It turned a 180 maybe 20 feet from my head and it was totally silent. The rising sun caught its back and it looked just angelic as it continued sectioning the field. Never did see the buck but I really didn't care.
The physics of how their wings are so quiet is really amazing.
I took an elective in during my bachelor’s degree where we studied how fish swim, birds fly, boundary layers of tree leaves, etc.
As part of it, we learned that owl feathers have microscopic hooks that are micro vortex generators. This causes a sound dampening during flight because there is next to no wingtip vortex (the main component of sound generation).
Really spooky when an owl suddenly appears right next to you when you are sitting in your tree stand. Happened a couple of times and I never heard a thing. My brother leaned out from his tree stand and an owl flew into him.
Thanks for posting that video! That was very well produced.
Yes, very cool stuff. The original stealth technology that's been around hundreds of thousands if not millions of years If given the opportunity, take a look at the leading edge of owl wings and the leading edge of their wing flight feathers and compare to most other birds. Most birds have wings with a somewhat sharp or smooth leading edge. It's where the "biot" sections come from for you fly tiers out there. That sharp or at least smooth edge cuts through the air as the bird flies. And all the exposed surfaces are smooth and somewhat hard. A more efficient way to fly, with less resistance. Of course as it cuts through the air it generates a sound or noise wave similar to a whistle's blade as it cuts through air. Owls' wing and flight feathers' leading edges have tiny projections, some call "hooks", along the leading edge. Those projections disrupt and scramble the air flow around the wing thus helping to silence the air cutting effect. The exposed surfaces of owl feathers tend to be soft and fluffy for lack of a better terminology, also intended to scramble the air flow. Additionally and on purpose, owls do not fly fast nor do their wings beat rapidly. The lower velocity of all their body parts moving though the air also minimizes any sound produced. Conversely, compare the silence of their relatively low speed flight to that of other raptors at full dive velocity! Raptors that dive on prey at high velocity sacrifice sound stealth for sheer speed. Falconers use such terms as "tearing or ripping paper" to describe that sound. Their prey can likely hear them coming and think about or start reacting but by that time it is too late! The sound generated by a raptor diving between 150 and 200 mph is impressive, just as is the silence of an owl swooping in slowly, making no sound.