Great silent hunter

During a recent Christmas visit to my parents’ house in my hometown of Dalhart, in the Texas Pan­handle, I was awakened by the low-pitched but loud call of a Great Horned Owl: ho-ho-hoo hoo hoo.

This article was named Outstanding Popular Article by the Texas Chapter of the Wildlife Society.

This wasn’t particularly unusual. I hear the owls during most wintertime visits to my parents’ house, but it is usually when I am outside the confines of the house.

My parents and I have had frequent discussions about their neighborhood owls because they own a Chihuahua and two of their three kids bring small dogs when their families come to visit. I doubt that a large owl sees much difference between such and, say, a jackrabbit or a coyote pup.

The owls have been in their neighborhood for years and often perch on poles, trees, and fences in and near their backyard. I have the same situation at my house near Canyon, south of Amarillo, where an owl often wakes us at night while participating in a duet with his mate from the top of our home.

That morning in Dalhart, the owl was obviously close. When I took my miniature dachshund pup, Lilly, out back a few minutes later, any call by the husky-­voiced male was quickly answered by the higher­-pitched hooting of a female. Her call rises in pitch at the end.

Keeping a close eye on Lilly, I listened to the owls’ conversation, trying to catch sight of the birds or at least to determine the direction from which they were calling. My dad had seen them a few minutes earlier. One was perched on a pole; the other was gliding silently across the yard.

Soon I heard a second pair join the chorus, from a distance, from the next home range over. The late fall and early winter is a noisy time for the species, as the owls strengthen or form pair bonds and establish nesting territories. All mated Great Horned Owls are permanent residents of their territories, but unmated and younger birds move freely in search of company and a territory and may leave regions with little food in winter.

Great Horned Owls occur from central Alaska across Canada to Newfoundland, and south throughout the Americas. They are found in a diversity of habitats, including canyons, deserts, forests, grasslands, and mountains and even in cropland and residential and urban areas.

The owls do not build their own nests other than some minor wallowing in the dirt of a cliff cavity or ledge, or in the litter of a tree cavity or broken-off snag. Occasionally, they may add feathers to line the nest but usually not much more. Most often, they take over nests used by crows, ravens, hawks, eagles, herons, or other large birds, and they will also nest on the top of old squirrel nests. I know a researcher who has found dead adult Swainson’s Hawks on the ground beneath nests taken over by Great Horned Owls.

Man’s influence has allowed Great Horned Owls to expand through the countryside in areas where, formerly, nesting structure was likely very limited. For example, in the western portions of the Great Plains, the species was likely restricted during the nesting season to areas of cliffs and on drainages where owls could take over other birds’ nests that were built in isolated trees or in groves of trees. In much of that region, native trees were few, historically. Today, nests can be found in introduced trees along roadsides, in towns, and at farmsteads. Ravens, and sometimes hawks, nest on utility poles and windmills, creating additional opportunities.

The owls will also nest in abandoned buildings and farm machinery and on haystacks and round hay bales. Last winter, I monitored a nest in a seldom-used two-story Quonset hut-like structure, where an owl incubated eggs that she had laid right on an old conveyer belt. While in graduate school in South Dakota, I found Great Horns nesting on round hay bales and on artificial nest structures placed in wetlands for ducks and geese.

Early nesters

Every year, Great Horned Owls will be among our earliest nesting bird species. Depending on latitude, they may call to each other as early as October. They choose mates or strengthen pair bonds with existing mates by December, and pairs are often heard singing synchronized songs, or duetting, before this time.

Females are larger than males, and individual variability can yield pairs whose members are noticeably different in size. An exceptionally large female (27-inch length, 60- inch wingspan) can dwarf a small mate (18-inch length, 36-inch wingspan). The male’s smaller size may help with agility for hunting and provisioning, or for nest defense. One can argue, too, that the female’s size can be pretty intimidating to a nest-site invader.

Normally, two to three but sometimes up to five eggs are laid, often as early as December in South Texas. I have found incubating Great Horned Owls in the central Panhandle as early as mid-January. Females do most of the sitting. Incubation lasts around a month. The young are brooded for a few weeks and remain in the nest for two and a half to three months, but sometimes much less.

It will often appear that the newly fledged young left the nest way too early, even before losing their baby down or becoming capable of flight. They are fed on the ground or some nearby tree or structure for a while and, once proficient of flight, will follow the parents around their territory, begging noisily. Gradually, the owlets will learn to hunt on their own and will disperse from their parents’ territories, usually by the age of 10 months.

The Great Horned Owl is a spectacular hunting machine armed with pinpoint sight and hearing and the ability to fly silently. It eats just about anything and everything, from insects to fish to other owls and animals up to two or three times its size. Cottontails and jackrabbits are the usual prey, but its diet is heavily influenced by what is locally available at the time. I read many years ago that most Great Horned Owl nests smell like skunk, because skunks are commonly consumed, and I do not doubt that skunks are taken, but I have never smelled skunk at nests. It is always fun to visit remote bat roosts at departure time, as they represent a highly concentrated food source. A gathering of Great Horned Owls often precedes the bats’ emergence.

And yes, Lilly, Great Horned Owls occasionally take small domestic dogs and cats, and right in front of their astonished owners. As a working biologist, I have received several phone calls about Fido or Fluffy being taken by this silent hunter. In fact, a fellow biologist had to ward off an owl that came after his year-old Labrador retriever while they were training on the grounds of a public school in Canyon. It is a common belief that any missing pet was taken by a coyote, but I believe more pets are taken by Great Horned Owls — by far — than by coyotes. In either case, it’s not too many.

Great Horned Owl populations are faring so well that most recent research has focused on their impacts on other species. The birds can cause dilemmas under specific circumstances. Certainly, they have their place in nature and are invaluable to us when it comes to rodent control. But they have created problems for biologists trying to reestablish or protect endangered species, especially colonial birds that nest in exposed situations.

A problematic predator

The Great Horned Owl is the only bird listed among the four problematic predators for the federally endangered interior population of Least Tern and the federally threatened northern Great Plains population of Piping Plover. Management plans for these species stipulate the relocation of owls to at least 60 miles from nesting colonies. They are also a major cause of mortality following releases of captive-reared Attwater’s Prairie-Chickens and Peregrine Falcons.

Out of concern for potential competition with the federally threatened Mexican Spotted Owl in Arizona, researchers examined how its diet overlapped with that of the Great Horned Owl. Although individuals of the two species share the same general area, they forage in different habitats. Additionally, Great Horned Owls concentrate on diurnally active prey, while Spotted Owls pursue prey that stirs at night. Thus, competition between the species is minimized.

In need of further study is how the Great Horned Owl affects other species in regions where man’s influence has allowed it to increase as a nesting species. For example, have grassland birds or rare species in the Great Plains had time to adapt to it? Behavioral or camouflage strategies take a long time to develop. Managers in the northern Great Plains are rethinking shelterbelt programs because they are providing habitat to predators where that habitat was formerly limiting.

I’ve always had a fascination with owls. As a youth, I monitored nests that Great Horned and Barn Owls placed in the rim of Rita Blanca Canyon, south of Dalhart. Even today, I work with Barn and Burrowing Owls, and I delight in listening to the calls of Eastern Screech-Owls and Great Horned and Barred Owls whenever I visit creek and river bottoms in the Panhandle.

The grand owl of them all is the Great Horned. His call is heard nationwide and, today, in all types of habitats. Truly, he is greatest among all of our aerial hunters.

 James D. Ray is a former Texas Parks and Wildlife Department biologist who has spent the last 13 years as the wildlife biologist for Babcock & Wilcox Technical Services Pantex, L.L.C., the managing contractor of the U.S. Department of Energy/ National Nuclear Security Administration’s (USDOE/NNSA) 18,000-acre Pantex Plant, near Amarillo. His work attained the USDOE/NNSA’s single allotted nomination for the 2012 Presidential Migratory Bird Federal Stewardship Award.

This article was named Outstanding Popular Article by the Texas Chapter of the Wildlife Society.

 

Originally Published December 1, 2012