Outstanding owls

A barn owl (Tyto alba) captured by one of our wildlife cameras at the Borderlands Wildlife Preserve.

There are approximately 200 species of owls recognized around the world that are found on every continent except Antarctica. They’ve adapted to thrive in all types of habitat, from snowy tundra to dense jungles, nesting in everything from saguaro cavities to palm tree bootjacks. Across their taxonomic order, Strigiformes, owls exhibit remarkable diversity in size, plumage and eye color, and hunting behavior. Some specialize in fishing, like the brown fish owl of Southeast Asia that preys on fishes, frogs, and crustaceans. Desert species specialize in small mammals and reptiles, insects, and even other owls. Great horned owls (Bubo virginianus) are known to prey on anything that is as large as they are; they can be up to 25 inches in length, with a three to five foot wingspan.

Great horned owl (Bubo virginianus) hunting for prey.

The smallest owl in the world, the elf owl (Micrathene whitenyi) only grows to about 5 inches tall and is found right here in the Sonoran Desert. Arizona is home to 13 species of owls, but the most common along the border near Patagonia are the great horned owl, barn owl, and western screech owl. Other less common species include the long-eared owl, whiskered screech owl, and the threatened Mexican spotted owl. 

Comparison video between a western screech owl. and a great horned owl.

Owls are known for their exceptional eyesight and ability to see in low-light conditions, but what makes them such lethal hunters is their hearing, which can pinpoint prey in total darkness with incredible accuracy. Many owls have asymmetrically placed ears, although studies show that this adaptation has evolved independently at least four separate times, and is not confined to a single family. For example a barn owl’s (Tyto alba) left ear is slightly higher on the head than the right, and they are slightly out of line with one another vertically. This means that sounds reach the owls ear milliseconds apart, which allows the owl to create a sound map and know exactly where the source is.

Barn owl seen at the BWP.

Owls also tend to have a flattened face with a disc of feathers along the edge that help to channel and amplify sounds to their inner ear. These traits vary across owl species, depending on what type of prey they specialize in hunting, and at what time of day. 

While owls are stereotypically known as nighttime creatures, many of them are most active during the dawn and dusk hours, which is known as being crepuscular. Some, like the northern pygmy owl, are most active during the day. An owl’s eye color can give away what time of day they tend to hunt during. Barn owls and spotted owls are nocturnal and have completely black eyes to help them camouflage - two bright yellow eyes would surely give them away. Other owls mostly have shades of yellow and orange eyes.

A side view of a barn owl at the preserve.

Owls are formidable predators because of the many unique and niche adaptations they’ve developed over the past 70 million years.

• Once owls capture their prey, they swallow them whole. Their digestive system doesn’t digest fur and bones, so owls regurgitate pellets. These pellets are ground up and compressed by their gizzard, a special organ that is like a second stomach in birds. 

• Another interesting anatomical feature of owls is their toe pattern, which is referred to as being “zygodactyl.” Their feet have two toes pointing forward and backward that can be flexed to look like an X or K. Woodpeckers and parrots exhibit this pattern, but owls and ospreys both have the ability to pivot one back toe to the front which allows them more flexibility when using their talons to capture prey on the fly. 

• Owls are also known for their ability to turn their head 270 degrees around (not quite 360, but definitely more than humans can). They have 14 vertebrae in their neck which allows them to be so flexible. But what’s even more fascinating are the blood reservoirs that fill when arteries are cut off during such intense and quick neck movements. 

• Owl eyes are actually fixed in place - they do not have peripheral vision and can not move them side to side within their socket, so being able to turn their heads so far is the only way for them to actually see their surroundings. But their fixed eyes enable incredible focus and depth perception which helps them locate their prey.

• Their silent flight then allows them to capture their prey. Multiple factors contribute to this ability - one is their relatively large wings in comparison to their body size, which allows them to fly unusually slowly by gliding and minimal flapping. Also, the leading edges of their flight feathers are soft and comb-like which break up air turbulence, which is what would usually create the typical swooshing sound we hear from birds wingbeats. These smaller streams of air are broken up even more by a soft fringe on the wings’ trailing edge.

A western screech owl bathes in a wildlife drinker at the BWP.

Owls play a critical role in pest control. Rodents and insects are primary food sources for owls, so owls naturally help keep their populations under control. Owls are also often seen as indicator species - if a healthy owl population is present, chances are the local ecosystem is thriving. I have been amazed by owls since I was a little kid, and after reading this blog, I don’t know who wouldn’t be. They are unique, beautiful, intelligent creatures that have adapted to thrive all over the world. But like many wildlife species, they are endangered by anthropogenic action: habitat loss, vehicle collisions, and rodenticide are the most common threats to owl populations. 

Poison accumulates in an owl’s body after ingesting rodents that have become contaminated, and the bioaccumulation ultimately kills them. Ironically, owls provide natural rodent control, but only if they have adequate habitat nearby to live and breed in. There are ways that individuals can help preserve owl populations, and in a world that feels so chaotic, action can be the best way to soothe an aching soul.

Great horned owl.

Even little habits like driving carefully at night, or replacing any rodenticide with mechanical and glue traps can make a difference. Keeping cats inside, installing nesting boxes, and planting native vegetation are all amazing ways to provide safer space for owls to live in a changing world.  Also, supporting organizations that promote land conservation and preserve open space is a great way to ensure that habitat remains for owls and all other species within their ecosystem. Owls deserve the space they need to thrive across all the different ecosystems they inhabit, and future generations deserve the opportunity to listen to the hoot-hoot of great horned owls, or watch burrowing owls march across the desert, and marvel at the full-moon face of a barn owl.