Burrowing Owl: The Underground Owl

by Ron Harton


On a Desert Survivor service trip one March, four of us were working the fence line along the Desert Tortoise Preserve. We hiked along the fence on the west side of the preserve replacing faded and damaged boundary signs and repairing damaged fence sections. The area right next to the fence was often rutted with motorcycle and vehicle tracks, yet the wildflowers were gorgeous. We paused in the cool, bright sunlight to enjoy and identify a particularly eye-catching patch of desert wildflowers.

Suddenly, right at our feet, a golden bird burst from under the ground and flew away into the preserve. It looked like a small owl with long wings. We walked over to the area where it took flight and there was a hole in the ground, open to the west and slanting back toward the preserve. A burrowing owl had emerged from its burrow and flown off in a decoying flight to distract us from its home.

Burrowing owls (Athene cunicularia) are small, golden brown birds. They have white spots on their brown backs and brown stripes on their white underparts. Their most characteristic feature is their long legs that make the bird appear almost cartoon-like. They take their name from their home–an underground tunnel. Adopting burrows left by other animals, the owls enlarge or modify them to suit their needs.

Burrowing owls live throughout the West. They prefer treeless flat or gently rolling land with holes and tunnels left behind by other animals. However, their habitat is disappearing, and the owl population is in decline. There are about 60% fewer owls in California now than ten years ago. The owls have been forced to try to adapt to developing areas and now use highway margins, railroad right of ways, junkyards, dumps, golf courses, and airports such as the Oakland airport for homes. They live throughout the western plains and desert areas. Their nests have been found at the bottom of Death Valley at two hundred feet below sea level and on top of the Dana Plateau in Yosemite at 12,000 feet. In the desert, their typical habitat is sagebrush scrub along fence lines and dry washes. They may be seen sitting on fence posts in rural areas.

In areas where the weather is mild, the birds are year-round, active residents. In the parts of their range which are subject to cold, the burrowing owls either migrate or remain for extended time periods in their burrows. Researchers at the Oakland airport found that the birds would stay underground for several days during cold or stormy weather. Some researchers have concluded that burrowing owls can go into a state of hibernation during the winter. Others have found cached food within the owl’s tunnels. One researcher, excavating an abandoned prairie dog town during winter, found a burrowing owl asleep six feet under ground. The burrowing owl is a real survivor–using a variety of methods to sustain life during difficult times.

Burrowing owls eat a variety of foods. Their staple is nocturnal insects. One study in Arizona found scorpions to be a favorite. They also eat rodents, but to a lesser extent than other owls. When their preferred foods aren’t available, they will eat just about anything, including lizards, baby birds, and spadefoot toads. They catch their prey in several ways. They are one of the few owls that hover. During the early evening, they can be seen flying low over the ground, then suddenly rising to hover over their target before diving. They can catch insects in the air or land and chase their prey, running on their long ungainly legs. Burrowing owls also still-hunt, sitting on fence posts or mounds of earth and waiting for prey to appear.

Nesting season depends on the elevation and weather. Since the owl’s main food is insects, nesting is timed so that the young may be fed during insect hatches. In mild climates, the owls may nest as early as March. In higher elevations and farther north, they may not begin until June or July. The male enlarges the burrow and nesting chamber. He uses his claws and beak to scratch at the dirt, kicking it backward out the opening. The opening of the tunnel and the burrow itself are sometimes lined with dried horse and cow dung. The owls may do this to camouflage the burrow and to insulate the eggs.

The female lays seven to eight white eggs in the nesting chamber of the burrow. The female incubates for about 28 days until the eggs hatch. The male feeds the female in the burrow and stands guard outside. He tries to scare away predators by a threatening series of bobs and turns, but he doesn’t hesitate to attack with his long claws, hurling himself at the predator with loud shrieks.

The baby owls are voracious eaters and grow rapidly. The male feeds the owlets and female for about three weeks. Then the female begins to leave the burrow to hunt, too. The owlets have a remarkable defense mechanism. When threatened, they emit a noise that sounds just like a rattlesnake. After they become mobile, the young begin to emerge from the burrow to stretch their legs in front of the opening, retreating at the first sign of danger. In only four weeks, the young are ready to leave the nest.

The parents don’t hang around the empty nest for long. The burrowing owl’s nesting burrow can become very messy. Owls swallow their food whole and then regurgitate indigestible parts in the form of pellets. This waste combined with the use of cow dung by the owls leads to infestation by flies, fleas, and other insects. Thus the parent owls vacate the nesting burrow soon after the owlets leave. The owls live in colonies when they can. In the past they lived along side ground squirrel and prairie dog colonies, utilizing their old tunnels. However, with the decline in those animals, the owls now often live alone.

To compensate for loss of habitat, naturalists in North Dakota have designed a burrowing owl tunnel and nesting chamber made out of wood. They have had success with it in pastures. The wood boxes are buried under a mound of dirt and the entrance camouflaged. Detailed construction plans may be found online or obtained from the North Dakota State Game and Fish Department.

We didn’t see the burrowing owl again that day at the Desert Tortoise Preserve. That night, though, while we were camped at the Pilot Knob Ranch section of the preserve, I heard the distinctive coo-hoo call of a burrowing owl out in the distance. Another owl answered, closer to me. I drifted off to sleep, listening to their conversation in the cool desert night.
 

BIBLIOGRAPHY


Grondahl, Chris and John Dockter. No Date. Building Nest Structures, Feeders, And Photo Blinds for North Dakota Wildlife. North Dakota Game and Fish Department, Bismarck, ND. Jamestown, ND: Northern Prairie Wildlife Research.http://www.npwrc.usgs.gov/resource/tools/ndblinds/ndblinds.htm. October 8, 1998.

Lambert, Mike and Alan J. Pearson. Owls and Birds of Prey. New York: Bonanza Books, 1989.

Ryser, Fred A., Jr. Birds of the Great Basin. Reno: University of Nevada, 1985.

Thomsen, L. “Behavior and Ecology of Burrowing Owls on the Oakland Municipal Airport.” Condor: 73:177-192.

Tyler, Hamilton A. and Don Phillips. Owls by Day and Night. Happy Camp, CA: Naturegraph, 1978.