GREAT HORNED OWL
TOP 5 ID TIPS: GREAT HORNED OWLS
Very large, stocky owl
Enormous bright yellow eyes
Mottled grey, brown, and tan body with bright white chin plumage
Tall feather tufts - which look like horns or ears - angled on the top of their head.
© KURT LINDSAY
GREAT HORNED OWL
Almost every person in North America has seen a Great Horned Owl at one point or another in their lifetime. This species even resides in parts of South America, too. With so many around, this bird has been deeply studied in the Americas. It has been found that these birds are extremely well-adapted to a wide variety of climates and ecosystems.
GREAT HORNED OWL HUNTING
An apex predator of the sky, the Great Horned Owl is well-equipped with various hunting tools. Long, sharp talons and strong feet allow these owls to grip their prey with up to 28 pounds of force, enough to severely damage a human’s fingers. A sharp, hooked beak is also lethal to prey animals and is an effective tool, used by the owl to rip flesh apart.
© Jon Bertsche
© Dick Walker
GREAT HORNED OWL VISION
The Great Horned Owl also possesses highly-equipped eyes, making low-light hunting much easier. This owl is considered mostly nocturnal and crepuscular, meaning that it is most active at night, or at sunrise and sunset.
A Great Horned Owl’s eyes are even larger in proportion to its brain than the eyes of other owls. This species has large pupils, designed to match their large eyes. Pupils are the black circles in the middle of each eye that function to allow the perfect amount of light into the rest of the eye. Surrounding the pupil of a Great Horned Owl is a bright yellow iris. This species shows a brighter tone of yellow than other owls due to an uncommon pigment in their iris known as xanthopterin.
Towards the back of the eye, they have a high number of specialized photoreceptors known as rods, which help the owl see well in low-light conditions but do not help with seeing colors. Since these rod cells make Great Horned Owls so susceptible to light changes, they are able to dilate and constrict their pupil quite quickly with the help of certain tiny muscles. Our eyes do this too; if you’ve ever turned on the lights too quickly in a dark room, you’ve felt the shock on your eyes! This is because your pupils were struggling to adjust quickly to the dramatic light change. A Great Horned Owl can actually constrict its pupils in 176 milliseconds or less after a flash of light. Dilation is not quite as fast, taking one full second for the owl’s eyes to adjust.
GREAT HORNED OWL FEATHERS
Great Horned Owls have soft, fluffy feathers that allow them to keep warm in colder climates. The color of these feathers depends partially on the bird’s home (location). Those taking up life in the Pacific Northwest of the United States seem to be the darkest, and those in the Pacific coast, California, and subarctic Canada seem to the lightest in color. Additionally, the species varies in size throughout their distribution map. Great Horned Owls residing in inland Alaska are significantly larger than those in the Baja California sur and the Yucatan Peninsula.
© Kurt Lindsay
GREAT HORNED OWL NESTING
Since these owls live in such a variety of ecosystems, they cannot afford to be picky when choosing a nest site. Great Horned Owls have been known to nest in trees, snags, cliffs, deserted buildings, on artificial platforms, ledges, pipes, the ground, and even in previously abandoned hawk or magpie nests, but do not build their own nests. They will, obviously, nest in urban areas, and are especially known to nest in the rafters of barns and other open buildings. Keep your eyes peeled for Great Horned Owls if you live in the Americas: many people live next to these owls without ever noticing!
© Kurt Lindsay
GREAT HORNED OWL THREATS
Although it is a treat for many folks when they see Great Horned Owls from their back porch or a roadway, there are downfalls to these owls occupying areas so close to humans. Great Horned Owls have reportedly died due to pesticide toxicity. How? If a farmer treats a crop field with a pesticide, and mice or other small mammals munch on that crop, they may become poisoned by the agrochemical compounds in the pesticide. Sick mice are easier for an owl to catch, so an owl might end up eating two or three pesticide-ridden mice or voles. Once the small mammals have been consumed by the owl, the pesticides will be absorbed into the body and could result in the owl’s death. This can also happen when people poison mice or other small mammals in their yards or properties using anticoagulant rodenticides. These are the types of chemicals bought at hardware or lawn and garden stores, which are meant to kill those pesky little rodents in your area. Unfortunately, although these are highly effective chemicals, an owl could consume the poisoned rat, mouse, or vole, and become poisoned as well. This is often referred to as “secondary poisoning”. Some studies say 11% or more of these owls are at direct risk for mortality by anticoagulant rodenticide chemical poisoning. Both pesticides and anticoagulant rodenticides have been reported as killers of Great Horned Owls, among other species of Birds of Prey.
Although few species prey of Great Horned Owls, others threats to the species include habitat loss and vehicle collisions.
Great Horned Owl who has been hit by a car and is being taken to a rehab facility.
GREAT HORNED OWL VOCALIZATIONS
Many people mistake Great Horned Owls for Screech Owls due to the misleading “screech” name. Keep in mind, if you hear an owl screeching, that does not necessarily make it a screech owl! Great Horned Owls are large birds with a loud, booming voice - the classic and most widely recognizable owl call. Although these owls are most commonly known for their deep “Whooo, Whoo, Whoo Whoo, Whooo-Whooo” call, female Great Horned Owls can also give odd-sounding squawk and screech calls. Many people mistake Great Horned Owls for Screech Owls due to the misleading “screech” name. Keep in mind, if you hear an owl screeching, that does not necessarily make it a screech owl.
GREAT HORNED OWL DISTRIBUTION IN NORTH AMERICA
© Kurt Lindsay
Map provided by The Birds of North America Online and the Cornell Lab of Ornithology.
GREAT HORNED OWL QUICK FACTS:
A large, bulky owl with prominent ear tufts, white throat, gray beak, and bright yellow eyes
Males: back is mottled grayish-brown, chest and belly are rusty brown and heavily barred
Females: same as male
Young: more orange-brown than adults, white throat less pronounced, ear tufts shorter
GREAT HORNED OWL SIZE:
Height: Males 51 cm (20.0 in), Females 60 cm (23.6 in)
Weight: Males 1304g (2.9 lb), Females 1509g (3.3 lb)
Wingspan: Males 134cm (52.7 in), Females 143 cm (56.2 in)
GREAT HORNED OWL RANGE:
Found year-round in all parts of U.S. and Canada except far northern coastal areas
GREAT HORNED OWL HABITAT:
Highly adaptable; can be found in a wide variety of habitats, including both coniferous and deciduous forests, swamp forests, mangroves, farmland, deserts, and even city parks
GREAT HORNED OWL DIET:
Mostly small mammals such as hares, ground squirrels, and voles; also preys on birds, amphibians, reptiles, fish, and insects
GREAT HORNED OWL VOICE:
Deep, booming hoots
Males: during breeding, a series of evenly spaced low pitched “hoo”s; to contact other owls or defend territory, often will give a soft, double hoot
Females: higher pitched than males
GREAT HORNED OWL NESTING:
Nest Site: a variety of nesting sites; most commonly abandoned nests of Red-tailed Hawk and other birds or squirrels, but also tree cavities, cactus, haylofts, manmade nest platforms, cliffs, and caves
Eggs: 1-4 dull white eggs, hatching about 2 days apart
Incubation: 30-37 days
GREAT HORNED OWL HUNTING HABITS:
Opportunistic but primarily a nocturnal perch hunter. Takes a wide variety of prey, often hunts along forest edges, meadows and patchily forested open country.
GREAT HORNED OWL CONSERVATION STATUS:
Not globally threatened; some decline of U.S. populations.
Owl Research Institute, All Rights Reserved
Arranged by Brooklin Hunt, ORI
“Great Horned Owl, Bubo virginianus”. Artuso, Christian, et al. The Cornell Lab of Ornithology Birds of North America. 30 May 2013. Birdsna.org.