Articles discussing the physical traits of barn owls, from eyesight to feathers.

Owl Feathers and Silent Flight

How Owl Feathers Allow Owls to Fly Silently to Catch Prey

The Feathers of Birds

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Down feathers keep birds warm, especially young ones.

Bird feathers, in general, have to be one of the most amazing creations in nature. The flight feathers of wings and tail enable birds to fly—not glide like flying squirrels—but fly powerfully from one end of the globe to the other. Down feathers insulate birds from cold. Contour feathers keep the birds dry in the rain. Powder-down feathers disintegrate into a talcum like dust that birds use to condition the other feathers.

Each feather is a work unto itself: Radiating out from the central shaft that runs up through the middle of the feather, individual vanes also contain barbs that hook over the next vane, and those barbs in turn have barbules that hook on to the barbs. This sophisticated arrangement makes for a very lightweight yet resilient structure. And when these various vanes and hooks become disorganized, a mere pull of a beak through the feather puts them all back together again.

Bluebird On A Stump

Birds use color to attract mates

Beyond these functions, feathers hold the brilliant, defining colors of sexual attraction. Since birds can see colors, various pigments evolve in feathers to make birds, especially the males, more attractive to lure a mate. But not all colors are pigments produced by the feathers. The reds in flamingos come from the foods they eat. And blues cannot be created inside the feathers, so they are created by the structure of the feathers—the soft brilliant blues of jays and buntings and the metallic sheen of purples and greens on grackles and blackbirds are created by infraction—illusory colors that work just the same.

Beyond displaying color to impress the opposite sex, the feathers of doves, pigeons, hummingbirds, manakins, and nighthawks are used in flight to whistle, hum, and boom to create “song” that attracts potential mates.

The Feathers of Owlsbarn-owl-flying

The feathers of owls have other, owlish purposes. These are refinements brought about by darkness and stealth and the quiet of night. As anyone should know who has ever heard a duck or a pheasant take off, feathers in flight create a lot of sound. Songbirds that eat insects and seeds have little need to be stealthy. The same is true for almost all birds.

Even the leading edge of the wing of a hawk through air creates a discernible sound as do the stiff tail feathers cupped to slow down before landing. But hawks use high speed and surprise to capture their prey in full daylight. Owls hunt in the quiet of night where their favorite prey, rodents, utilize their hearing to detect potential predators. Since rodents have poor vision but relatively good hearing, owls rely on being quieter than a whisper to capture their food. This is accomplished by their special feathering.

While the leading edge of a hawk’s wing is sharp and defined (and thus noisy), the leading edge of an owl’s wing contains a serrated, comb-like structure that breaks up the air as it passed over the wing. This soft combing of the air results in almost no sound being produced. In addition, the feathers of the wings, body, and tail of owls are wider and rounder than those of other birds and, to further reduce sound, they are cloaked in a soft, velvety covering of tiny feathers that also soften their passage through air. The result is almost totally silent flight.

Calling Owls in the Wild to Experience their Silent Flight

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Red-phase Screech Owl

Try using a tape of owl calls to call in common owl species in your area. You will notice that, if you do not happen to glimpse the owls arriving, the first thing you will hear will be their singing in response to the tape. They will arrive soundlessly, like ghosts. Their prey also never hears their arrival and must rely on their poor eyesight under dim conditions to detect danger from owls.

The combination of silent flight and excellent hearing creates a perfect nighttime predator in owls.

Barn Owl Hearing

The Phenomenal Hearing of the Barn Owl

Owls, being nocturnal hunters, have excellent hearing in general, but barn owl hearing exceeds even that of most owls.

barn-owlOf the 216 species of owls in the world, 200 belong to the Strigidae family. The 16 barn owl species belong to a separate family, Tytonidae. This means that the two groups have different lineages and, therefore, possess different traits. Despite the excellent hearing present in the owls of the Strigidae, barn owls have been shown to possess even more refined hearing than most other owls.

Barn Owl Hunting Behavior

Barn_Owl_Flying_8349Anyone who has ever watched a barn owl hunting in twilight – a pale apparition hovering and quartering across an open field – also will notice how the barn owl keeps its head down, its face pointing studiously toward the ground. That face bears some examination. No other owls possess the pronounced concave facial disk that barn owls possess. This facial disk, created by the feathers to form a hollow disk around the entire face, operates very much like a satellite dish—capturing and locating sound. To either side of the disk sit the two ear openings and these, like other owls, are positioned slightly asymmetrically, another adaptation to allow for greater accuracy in pinpointing the exact location of a sound.

Barn Owl Facial Disk

Three barn owls about 4 weeks old

Young barn owls developing their facial disks

The effect of the facial disk is similar to what happens when you cup your hands toward a sound in order to hear it better. The cupped hands collect sound more efficiently than open air. By turning its face toward the ground, the barn owl collects sounds far more efficiently than your cupped hands. Then the asymmetrical ears send the sounds to the brain with two slightly different signals that allow the barn owls to pinpoint the exact location.

So acute is barn owl hearing that, in a research experiment, barn owls housed in total darkness were able to capture live rodents on a bed of dry leaves with stunning accuracy. Of course, this ability to hunt “blind” is also utilized when barn owls plunge their legs into snow or high grass to capture prey. And since barn owls tend to capture a higher percentage of pregnant female rodents than exist in the population, it is theorized that they may be able to differentiate rodents according to age and sex. This would be accomplished by discerning the difference in sound made by larger, heavier bodies moving through vegetation, or even the difference in the sounds made by different sexes and ages while chewing on grass or seeds.

Pocket gopher foraging at feeder hole

Pocket gopher foraging

In my research project in California where we are measuring the effect of a barn owl population on the rodent population, I frequently see pocket gophers foraging. These rather large rodents are some of the most cautious animals in the world. They use “feeder holes” to forage above ground. In their effort to reach plants to eat, they stretch their bodies out sometimes almost all the way, but never allowing the tip of their tail to leave the feeder hole. This allows them to know exactly where to retreat to from danger, and this they do frequently, whether danger is present or not. The idea of capturing one of these fast moving, cautious creatures by hand seems out of the question, no matter how much stealth could be applied. Yet, I have recorded a male barn owl capturing two pocket gophers in under five minutes on a dark, moonless night and delivering them to his female and chicks.