Incredible Owls and How to Protect Them

barred owl

Flying blind isn’t a problem when your whole face listens!

Have you ever seen an owl’s ears? Probably not, because they are hidden in their facial feathers! Most owls have a facial disc, and their ears sit inside the perimeter of the disc.

Some scientists refer to an owl’s entire face as an ear. Owls have round, satellite dish-shaped faces that are designed to detect sounds. This form has a similar effect to what happens when you cup your hands around your ears and aim them toward a sound to hear it better - your cupped hands collect sound more efficiently than open air. An owl gathers sound far more efficiently than we do by turning its head toward the sound. At certain frequencies, an owl’s hearing is 10 times more sensitive than ours. An owl can also alter the shape of its facial disc by using special muscles to channel sounds at will. 

The facial disc is made up of stiff feathers called a ruff, which form a curved wall around an owl’s face and acts like a reflector for sound. The ruff increases the surface area over which sound is collected, increasing sound sensitivity by about 20 decibels. To make their hearing even more acute, many owls’ ears are placed asymmetrically on their heads.

What in the world do lopsided ears do for hearing? They catch sound at different times, allowing the owl to pinpoint locations of their prey with deadly accuracy! This unique adaptation allows the owl to determine what height and direction  a sound is coming from. Asymmetrical ears send the sounds to the brain with two slightly different signals that allow owls to pinpoint the source.

For example, a barn owl’s left ear opening is higher than the right, so a sound coming from below the owl’s line of sight will be louder in the right ear. The translation of left, right, up, and down signals are combined instantly in the owl’s brain and create a mental image of the space where the sound is located.

What kind of brain capability does it take to process all this information? A fast one!

Studies of owl brains have exhibited medullas, the area of the brain associated with hearing, that are much more complex than other birds. A barn owl’s medulla is estimated to have at least 95,000 neurons, three times as many as the very intelligent crow.

Think of the owl’s medulla as a triangulation calculator. Triangulation works like this - imagine a triangle with one short side and two long sides, (isosceles for those who remember geometry). The short side is the base, and the two long sides meet at a sharp point. Imagine a mouse at the point and the base of the triangle is the distance between the owl’s two ears. The long sides trace the distance from each ear to the mouse. To triangulate sound, the owl turns its head. When the two sides of the triangle are equal in length, the sound is arriving at both ears simultaneously, and the owl knows it is directly facing its prey. Owls can detect a left-right time difference of about 0.00003 (30 millionths of a second)! Owls inherently triangulate sound and can do so in rapid sequence and while flying. 

Owls are “wait and see” predators, sitting on a tree branch waiting for their prey to run by. Once they take off in conquest of their dinner, they must continually listen for the prey to see if it has changed its direction, which means the owl must redirect its hit. If the prey moves, the owl must be able to make corrections mid-flight. When it is about 24” away from its prey, the owl will bring its feet forward, spreading them in an oval pattern. Just before striking, it will thrust its legs forward in front of its face, aiming for the kill. It’s like a military plane locking in on its target and following it. Even if the owl cannot see its prey, it can hear it. Flying blind isn’t a problem when your whole face listens!

An owl’s beak also plays a role in sound reception. The beak is pointed downward, increasing surface area over which sound waves can be collected and redirected to the ears. Now you can see why some educators and scientists refer to the owl’s entire face as an ear.

How does the ear actually process the sound it receives? Similar to a mammalian ear, the owl ear has three regions - outer ear, middle ear, and inner ear. Sound reaches the ear in pressure waves that are channeled toward the eardrum, which is located in the middle ear region. An owl's eardrum is proportionately larger compared to other birds. These airborne sound waves then travel through the eardrum and a single bone and are transformed into fluid-borne vibrations, which trigger thousands of tiny hair cells in the inner ear. Sounds with different frequencies reach different parts of the inner ear and trigger the hair cells to move, resulting in signals that build a complex picture of these different sounds.   

Being quiet as a mouse is not much defense against stealthy owl hearing.

great horned owl

Now that you know you have a superhero with superpower hearing living in your woods or yard, please stop and consider the choices you may make that can affect this spectacular creature.

Owls are nature’s pest control — they don’t even charge for their services! A barn owl will typically eat 3-4 prey items (mostly rodents) a night. During breeding season, a pair of barn owls will have one to two clutches, and hopefully find this amount to feed each of the five to seven chicks in a clutch. This adds to upwards of almost 4,000 prey items a year to feed a pair and their offspring. That’s some serious free pest control!

If you don’t have a barn owl in your vicinity, you might have great horned owls, barred owls and eastern screech owls that also contribute to rodent consumption, in addition to the many species of hawks. We have an ethical commitment to conserve birds, but according to the American Bird Conservancy, they also provide billions of dollars' worth of insect and rodent control, plant pollination, and seed dispersal. So my question is... why are we willing to poison owls and other wildlife in order to fight rats that get into our buildings and homes? 

Poison wildlife, you ask? How?

It’s quite simple: rat poison. If someone has a rat problem, they usually put out poison, or they contract a pest control company to put the poison out. Rat poison is trophic, meaning it travels through the food chain. Rat poison is an anticoagulant, causing its victim to bleed to death. Affected rats stagger about, dazed and looking for water for days before they die. They become easy targets for wildlife, and the poison in the rat crosses to the raptor or other wildlife consumer. Wildlife that isn’t killed outright by the poison can easily bleed to death because their blood fails to clot. 

Now imagine the barn owl, with a nest full of hungry chicks, who repeatedly catches poisoned prey. “If you’re just getting one dose on top of another, you get this constant exposure,” said Nancy Golden, a U.S. Fish and Wildlife Service toxicologist. “It’s one thing to have enough to kill the animal outright. But what about the ones that are just carrying this body burden? What effect does that have on their fitness?”

According to Scientific American, these sublethal effects are difficult to gauge, but research suggests they are real. For example, a study at McGill University in Montreal allowed a sparrow to perch on a pesticide-laden surface, absorbing pesticide through its feet. Then researchers put the sparrow into a big cage, along with three undosed sparrows and an American Kestrel, a small falcon that eats sparrows.

Although the scientists could not see any differences in the behavior of the pesticide-dosed sparrows, the kestrel apparently could. In 12 of the 15 instances in which the kestrel preyed on one of the sparrows, it picked the one that had absorbed the pesticide. Though that study did not involve rat poisons, it shows that animals not visibly affected may be extremely vulnerable.

Other non-targeted animals that may fall victim to poisons include opossums, bobcat, fox, coyote, hawks, and skunks, to name a few. Eating a poisoned rodent may kill them or seriously compromise them. When they die, their body may be consumed by another animal, which may also receive a dose of poison. And the cascade continues.

If you’ve got a few rats invading your domain, buy some rat traps, bait them with peanut butter, and wait. If you don’t want to handle this yourself, or if your invasion is large, call a pest control company and request non-trophic bait. No bait is a 100% guarantee that it will not travel through the food chain, but you should request its use. I have chickens, dogs, and lots of wildlife in my yard and neighborhood,  and I had a large rat problem. My pest control company understood my desire to use non-trophic bait. After several baitings, the rats went away, and my animals and wildlife were safe.

We also should be mindful of the pesticides we use in our gardens and on our shrubs and grass. These can cause death to many beneficial insects, especially pollinators. Those companies that offer to spray your yard for mosquitoes? The pesticide may kill beneficial insects, too. Get educated and ask lots of questions before deciding to do this. The effects of pesticides, whether they are used to protect plants or directly target insects, can be devastating. They often kill all the insects in the area, not just the harmful ones. Also, consider predatory insects to keep harmful pests from chomping on your prized veggies. Good bugs keep the bad ones in check far better than you can.

Just remember, everything you do affects our animal neighbors. Be responsible in your choices.