Great-horned Owl

Name

The genus name Bubo comes from Latin for “a horned owl” or “owl of ill omen.” The species name virginianus refers to the state of Virginia, where this species was first described. The common name of the great-horned owl refers to its prominent ear tufts.  

General Description 

Great-horned owls are difficult to misidentify given their large size, noticeable ear tufts and distinct plumage. Both sexes look alike in coloration and pattern. Plumage is a combination of sooty brown, cinnamon, and dusky gray, with barring on the breast. A white throat patch is often visible from the front. Their tail is brown with 5 to 6 dark bars, their facial disk is cinnamon colored with black around the edges, talons and bill are black, and eyes are yellow. Juveniles have white and gray downy feathers on their back and wings, giving an overall fluffed impression. They have less prominent barring than adults, and more gray and rusty pigment. Ear tufts are smaller and less noticeable.  

Similar Species: Long-eared owls can be mistaken for great-horned owls given their prominent ear tufts. However, long-eared owls are two-thirds the size of great-horned owls and appear narrower overall. Screech owls are often mistaken for young great-horned owls; in actuality there is little aesthetic overlap aside from their shared ear tufts. 
 

Vocals

Great-horned owls are one of the few owls that actually hoot. Their recognizable “Whose awake? Me toooo” vocalization can be heard across North America. However, like other owls, great-horned owls exhibit a repertoire of different vocalizations indicating various behavioral states such as territorial defense, sexual excitement, begging, and distress. Individual great-horned owls can be told apart based on the number of notes they give, as well as the interval between them. 

Click to hear a sound clip!
 

Habitat 

Great-horned owls are one of the most widespread raptors in North America, occupying deserts, rainforests and virtually every habitat in between. Renown author Scott Weidensaul said in his book Owls of North America and the Caribbean, that listing the habitats where great-horned owls are not found would be easier than listing where they are. They especially thrive in fragmented edge habitats, and exhibit adaptability in human-dominated landscapes. They are found less often in open fields or dense interiors of mature forests, although nesting does occur in the latter, potentially because of the greater maneuverability afforded in forests with less undergrowth. 

Great-horned owls often roost in conifers or dense deciduous trees that offer concealment during daylight hours, though crows are notoriously adept at harassing great-horned owls regardless of where they are “hidden” or not.   
 

Feeding

The diet of great-horned owls reflects their adaptive lifestyle. Although they prefer mammals, they commonly dine on birds, reptiles, amphibians, insects, fish, crustaceans, carrion, and even scorpions. A hungry great-horned owl will eat what is available. Studies show that mammals compose roughly 90-94% of biomass in the diet of great-horned owls from several North American sites, while birds make up 5-11%. These percentages are, of course, dependent on where the birds are living; for example, a nesting pair in North Dakota fed their nestlings 90% birds, while pellets beneath one Pennsylvania nest were filled with catfish remains. Adding to the uncertainty of dietary assessments is the fact that body parts of some prey, such as small songbirds, do not preserve well in owl pellets and therefore may be underrepresented in pellet studies.

Great-horned owls will eat other raptors, and readily hunt red-tailed hawks, osprey, red-shouldered hawks, nestling bald eagles, other owls, and even on occasion other great-horned owls. These interactions do not always end well for the attacker; great-horned owls have been found bearing evidence of snake retaliation, puncture wounds from hawk talons and embedded porcupine quills. 
 

Nesting

Courtship begins as early as autumn, making great-horned owls one of the earliest breeding raptors in North America. Pair-bonding, hooting and beak rubbing are the primary courtship behaviors. The white throat patch is often exposed during hoots, potentially as a signal during low light conditions. Researchers theorize that pairs may stay together for life, though this has not been empirically proven. 

Great-horned owls use secondary nests (most often former red-tailed hawk nests) located in trees, caves, cliffs, and even old buildings. Same-species nests in selected study areas are typically 1.6 kilometers (1 mile) apart, although this pattern of distance might also be the result of red-tailed hawk nest distribution. Females in mid latitudes lay eggs between December and January. Such an early nesting date gives great-horned owls top choice of sites, providing an advantage when space or nest quality is a limiting factor for prospecting birds. 

Incubation lasts for an average of 33 days and is done entirely by the female. Clutch size ranges from 1 to 5 eggs with an average of 2. Great-horned owls are capable of double-clutching, meaning that if the first clutch fails the female may lay another. However, usually fewer eggs are laid the second time, and they are smaller. 

Nestling great-horned owls eat what their parents eat, although as one would expect, the amount of biomass brought to the nest is linked to the efficiency of the parents, the availability of prey, and the number of young. Each nestling is fed roughly 300 grams (10.5 ounces) of food per day, and size of prey increases with nestling age. 

Flight feathers emerge around 5 to 6 weeks of age, around the same time that nestlings begin experimenting with their mobility, jumping around on branches and sometimes ending up on the ground. This stage is called the “branching” stage. Fledging occurs around 9 weeks of age, although like other large species such as snowy owls, the fledglings remain within their parent’s territory until autumn or later. They learn to hunt while still benefiting from the protection of their parents, and therefore young great-horned owls have a relatively high survival rate.   

Migration

Great-horned owls are mostly residential (non-migratory). Although northern subspecies may move south during winter, a study conducted in the Yukon concluded that during the summer, pairs rarely moved more than 3 kilometers (1.8 miles) from breeding territories held the year before. Great-horned owl winter irruptions (see snowy owl species account) do sometimes occur in response to snowshoe hare population cycles; however, the trigger seems to be a low abundance of hares, rather than a prey surplus, as is the case for snowy owl irruptions. During low hare years, northern great-horned owls may move south. Juveniles are more likely to disperse than adults, as they are scoping out territories and learning the ropes.