Silent Owl Wings

These beautiful birds move on silent wings. Try as we may, it is nearly impossible to hear the sound of an owl coming or going, so they often take us by surprise.

The secret to their stealthy movement lies in the design of their feathers. When air flows over a typical bird wing, turbulence is created, causing a rushing sound. Most bird feathers are stiff and rigid with almost pointy edges.  When air hits them, turbulence is created, causing sound.

Owl wing feathers have several ingenious designs that greatly reduce sound, especially when the wing tilts as the owl nears its prey. The leading edge of the owl's wing is covered with tiny comb-like structures that break up the incoming air into many micro pockets of turbulence. Those smaller gusts of air then flow over the owl's wing to the trailing edge which is made up of a soft fringe and separates or muffles sound even further.  Any remaining sound is absorbed by the downy feathers on the owl's legs and wings.

Owl wings are also larger and wider than the wings of most birds of prey, which gives them more lift so they don't have to flap as often.  Their large wings make them slower, but the combination of size and unique feather features create the perfect design for the nocturnal owl.

Check out these amazing videos which demonstrate the silence of owl flight when compared to other birds.
BBC - Super Powered Owls
KQED - See What Makes Owls So Quiet and So Deadly

Reference and Resources
Ask Nature

Nature

Image - Public Domain Pictures

Desert Welcome

We are back in the desert after a summer and fall in the Pacific Northwest.  As we drove the final miles to reach our little house on the hill, we were treated to a dramatic night sky filled with banks of clouds illuminated from behind by a huge moon.  It is a sight that I associate with the vast southwest deserts and I had forgotten how much I love our dark star-studded night sky.

The desert creatures were also here to welcome us.  As we turned into our neighborhood, two clumsy javelina clambered across the road and a road runner flitted into the brush, startled by the sudden light of our headlights.  The house seemed quiet, but one scorpion waited in the guest room to remind us that we were no longer in the innocent northwest.  We were back in the dry land of prickles, stings and fangs.

The stark contrast between the two environments is always so vivid at first.  How our planet can sustain such different biomes, each filled with flora and fauna that thrive in such extremes is yet another design mystery.

Image - Sharon Pegany

Harris Hawk

Tonight was a beauty.  The sky was streaked with pastel pinks, purples and sapphire blues.  As I made my way out to owl rock, I noticed the movement of a large bird lifting dramatically over an area of granite boulders. I was able to catch the flash of a white stripe on the tail and quickened my pace, hoping to get closer look.  To my amazement, I not only met the bird, but also his handlers, as well as another bird. They were traveling in a small group and had harnesses and poles on which the birds could perch.

These two Harris Hawks have damaged wings and can't be returned to the wild.  I thought of the sight of a free hawk, soaring high in the sky, and I felt a pang of sadness. Of all animals, birds seem to have the most freedom, so when that freedom is lost, it is even more tragic.

Harris hawks are common in the southwest deserts, but engage in an uncommon practice called "back-standing." Three or four birds can be seen stacked up on one another like circus performers trying to impress a crowd.  By standing on top of one another, the bird at the top may be able to see farther and spot prey.  It could also provide shade. Only the hawks know the purpose, leaving us to speculate and wonder... another design mystery.

Spotting harris hawks in the Sonoran Desert is relatively easy.  Unlike most hawks, they are social birds, so they can be seen in small groups, protecting nesting areas or hunting together.  They are dark brown with rusty red and white markings.  Their long legs are yellow and they also have yellow on their faces.  You may hear their loud, harsh call before you see them, but follow the sound and you may be treated to a back-standing session or a playful game of leapfrog as they fly from rock to rock.

References and Resources
Desert Museum 
All About Birds
Bird Sounds - Harris Hawk

Image: Public Domain Pictures and Sharon Pegany

The Owls Are Back

The great horned owl is the largest owl in the Sonoran Desert,
reaching a height of 2 feet and a tip to tip wingspan of 4-5 feet.

In the Sonoran Desert, our November evenings are nearly perfect for enjoying the night air and observing some of our nocturnal neighbors.  For several nights, we have heard the unmistakable scratch of talons on our chimney, followed by the throaty hoot of the Great Horned Owl. One loud series of hoots is usually followed by a distant call of another owl answering back. We sneak out our back door to catch a glimpse of these magnificent raptors and to listen to their cryptic conversations filling the night air.

November is the time when male great horned owls begin setting up territories in preparation for breeding and nesting. Their calls may be warnings to other owls that they may be in claimed territory. Most great horned owls mate for life, and starting in October, the pair begin their rituals of courtship which include passionate calls back and forth. Adults also make other sounds including whistles, shrieks, barks, coos, hisses and can loudly snap their bills if defending young.

Tonight, open your windows and tune your ears to hear this distinctly autumn sound.  If you live on the edges of wilderness, the owls are probably there.

To hear recorded sounds of the great horned owl:
All About Birds - Owl Sounds

References and Resources
Desert Museum
Nature Blog

Image: Public Domain Pictures