EAR TUFTS – An adult great horned owl perches in a cottonwood at Pilgrim Hot Springs. Great horned owls are named for their “horns” or "ears” that are tufts of long feathers, unrelated to hearing. Only some forest owls have these prominent tufts. The tufts are thought to break up the owl’s silhouette and help camouflage it in its branchy forest environment. Raising and lowering the tufts may also aid in nonvocal communication.BEGGING — A young owl begs for food. While I was photographing the adult great horned owl on the left, the young owl on the right landed on the branch and tentatively approached its parent to beg. The parent turned to face the youngster and seemed to say “get your own” before flying away. Parents continue to feed their young into the fall as they learn to hunt for themselves. But they roost away from the young to avoid their frequent demands for more food. OWLET IN A STICK NEST — One of two owlets is resting in its nest in a cottonwood tree at Pilgrim Hot Springs. Great horned owls do not build their own nests. They often use abandoned raven nests, as they did in this case. When the owlets are five to six weeks old, they begin venturing from the nest onto adjacent limbs, as this bird’s sibling was doing. Pilgrim Hot Springs has long been a nesting site for great horned owls. Jim Dory took this photo during the 2009 Northwest Campus birding

Great Horned Owl –– A top predator of the forest

Recently I visited the cottonwood groves at Pilgrim Hot Springs and Council’s spruce forest, hoping to get better acquainted with a magnificent forest predator––the great horned owl.
 Great horned owls are one of the most common owls of North America. They are found primarily in forested habitats across the continent, as far north as treeline. In Alaska these owls are common residents throughout interior forests and are found less often as far west as forests extend.
On the Seward Peninsula, deep hoots and occasional sightings of these formidable hunters can be seen and heard in spruce forest habitats and large cottonwood stands. There, a few of these owls breed and stay on their territories throughout the year.
Rarely, great horned owls venture beyond the forests and turn up briefly in surprising places––on the porch of a Nome house in January 2013, and in shrub habitats near Nome. These owls are nonbreeding “floaters” that have not established territories.
Home ranges of this large owl usually include open areas such as wetlands or meadows where they hunt, as well as the forest where they perch, roost and nest. This ideal mix of habitats occurs at Pilgrim Hot Springs, and explains the longtime use of that area as a nesting locale.
Breeding pairs are monogamous. They may occupy their territory for many years, year-round, defending their claim by hooting. Both males and females sing, but territorial hooting is mainly by the male. Their deep “who, who-who, who, who” resonates through the forest throughout the year, but pairs are especially vocal in winter during courtship when they “duet.” Then, you can notice the calls differing in pitch, the male having a deeper voice.
Though inhabiting the same territory, the pair seldom interacts except during the nesting season. Courtship involves bowing and duetting.
Great horned owls do not build their own nests. Rather, they often occupy an abandoned raven or raptor stick nest, usually in a tree, or use a natural tree cavity, a broomed spruce, a dead snag, old buildings or other manmade structures, cliff ledges, or occasionally they may nest on the ground.
These owls have rather spartan nesting habits, using little nest lining other than some downy feathers plucked from their own breasts, or they may use no lining at all. They do no nest maintenance, so they are seldom able to occupy the same nest twice.
Nesting begins in late winter in the north, giving the young time to learn to hunt before the next winter. The female lays one to four eggs, which she incubates for 30 to 37 days. Eggs hatch two days apart; thus, the older chicks are larger and more likely to survive if food is scarce.
Newly hatched owlets are mostly naked with closed eyes, but they quickly grow a covering of white down. The female incubates the eggs and broods the young for the first couple of weeks after hatch. Her mate delivers meat to the nest, which she tears into small pieces to feed the chicks.
After the brooding period, both parents hunt food for the young. At five to six weeks, the young begin “branching” and venturing out onto tree limbs or other features near the nest. In nine to ten weeks the owlets begin to fly. The parents continue to provide food for several months as the young learn to hunt.
Great horned owls have been called “tigers of the sky,” inspired by their terrific hunting prowess and ability to take a wide variety of prey, including animals larger and heavier than themselves.
The owl’s short, wide wings are adapted for maneuvering through the trees, but these wing proportions are not good for prolonged aerial hunting. Thus, great horned owls are mainly perch-and-pounce hunters.
As evening approaches, the owls typically perch in a tree along the edge of a meadow or an opening in the forest to look and listen for prey. Their acute hearing and keen vision enable them to detect and hunt prey in low light conditions. They hunt primarily in the dusk to dawn hours, even in the light of a northern summer.
The eyes of great horned owls are exceptionally large relative to brain size, even compared to other owls. Their pupils open widely in the dark and their retinas have many rod cells, providing them with superior night vision. Unlike other birds, their eyes can’t move in their sockets and can only look straight ahead, but their heads can swivel more than 180 degrees, allowing them to look in any direction.
Their acute hearing is enhanced by large facial disc feathers that direct sound waves to their ears. When hunting they can erect these feathers slightly to increase the cupping effect, enabling them to hear the slightest movements in the grass or sounds of wings in motion to pinpoint prey.
When prey is detected, they swoop silently down to grab their quarry in a death grip, severing the spine with their strong, feathered feet and sharp, curved talons. A four-pound great horned owl can lift up to six pounds of prey with its short, powerful wings.
Great horned owls have the most diverse diet of all North American raptors. They favor mammals, especially snowshoe hares, but they will eat whatever they can catch, from voles to mammals and birds larger than themselves. Insects, fish and carrion are on their menu, too. They are even known to hunt porcupines, but that encounter is usually fatal to both the hunter and the hunted.
In the north, the owls may store uneaten prey and “incubate” it to thaw it out.
Great horned owls are at the top of the food chain. Adults fear few enemies, but unattended eggs and young may be preyed upon by foxes, raptors or ravens. Adults respond fiercely to intruders with bill clapping, hissing and screams, and may unfurl their impressive wings and strike with their talons. They occasionally kill other great horned owls.
Like all predators, they are subject to harassment by other birds. Ravens, songbirds, and raptors often pester owls with loud calls while dive bombing, chasing and pecking at them. This draws attention to the predator so prey won’t be taken by surprise.

Great horned owls have no regular, annual migration. Mated pairs are generally permanent residents. However, when winter prey is scarce, especially when hare populations crash, owls may travel long distances and erupt in large numbers in areas where food can be found.
Great horned owls are adaptable and opportunistic––characteristics that bode well for their future in our rapidly changing world. They are tolerant of people, at home in many habitats, have a diverse diet and use many types of nest sites.
Northern populations rise and fall as prey populations cycle, but they are widespread and common and their numbers are generally stable in most areas. Happily, for now, these magnificent owls are a species of low conservation concern.

 

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