This image shows one of those unique adaptations of owls that I seldom see in my photos. I photographed this juvenile Burrowing Owl just over two weeks ago after it took off from its fence post perch in Box Elder County, Utah.
1/3200, f/7.1, ISO 640, Canon 7D Mark II, Canon EF500mm f/4L IS II USM +1.4 tc, not baited, set up or called in
The crisp flight feathers of most birds make a very noticeable gushing noise as they pass through the air, as anyone who has been close to a bird in flight as it flaps its wings is well aware. This would be a distinct and obvious disadvantage for nocturnal hunters like owls who hunt by stealth at night. But one edge of most owl flight feathers is fimbriate (fringe-like) rather than “crisp” (imagine the fringe on the edge of a scarf). This fringe breaks down the air turbulence into small groups called micro-turbulences that effectively muffle the sound produced as air rushes over the wing surface and allows owls to fly silently. One theory suggests that the fringing actually transforms the sound energy to a higher frequency that most critters, including humans and prey, cannot hear. Silent flight allows owls to use their own hearing to stealthily locate prey at night.
The position of the wings and the relative sharpness of their tips in this image allow us to see the fringing on the tips of at least four of the flight feathers of the right wing. I’m sure that many of my readers are well aware of this characteristic of owls but I thought it was interesting to see the fringing in a wild bird in flight.
The effectiveness of the fringing is dramatic and education birds are often used to demonstrate that fact to the audience. Typically the educator first holds a hawk or falcon on the fist as the bird is raised and lowered causing it to flap its wings. The noise produced by the wings is loud and can be distinctly heard some distance away. Then the very same thing is done with an owl and when it flaps its wings in response there is virtually no sound produced.
Folks who see this demonstration are usually quite impressed by the contrast. When it was done for my Zoology and Utah Wildlife students when I was teaching it definitely left an impression.
Here’s a link to an excellent video clip that demonstrates silent flight in a Barn Owl if you’re interested.
Note: I have a question. Multiple internet sources refer to the fringing as being on the “leading edge” of the primary wing feathers. But this image and other experience I’ve had with owl feathers suggest to me that the fringing is instead on the “trailing edge” where most of the air resistance is. I can be a little dense at times (especially after a long night with little sleep because of extremely annoying fireworks in my neighborhood) so I’d appreciate some enlightenment on the subject. What am I missing?…