Getting to know the Great Horned Owl
Our great horned owl is nesting in a loblolly pine about 85’ feet up, on the edge of one of our golf courses and adjacent to a wide expanse of salt marsh in coastal Georgia. She is using the nest built by a bald eagle pair that nested and fledged young in 2013 and 2014.
While we expected the eagles to return, only one of the pair visited the nest this season, and while we thought they were moving back in, the mate never showed. Nature has served up an alternative and we are excited to watch and to get to know more about Bubo virginianus, informally known as the hoot owl.
Our partnership with the Cornell Lab of Ornithology dates back to the installation of the bird cam in July 2014. The live streaming video and expert commentary [coming soon] are made possible through this valuable partnership. The video stream can be seen on our site (LandingsBirdCam.com), and will soon be available on the Cornell site (allaboutbirds.org) and the Georgia Department of Natural Resources Site /www.georgiawildlife.com/cams
GREAT HORNED OWLS are some of the earliest breeding birds in North America. In courtship the male will hoot emphatically for about a month or six weeks. The female hoots back, but only for a week to 10 days. The male may convince the female by bringing her freshly caught prey. Pairs typically breed together year after year and may mate for life.
Males select the nesting site. Great horned owls, like all owls, do not build their own nests. Most tree nests are those constructed by other animals, often taking over a nest used by some other large bird, like our eagles’ nest, sometimes adding feathers to line the nest but usually not much more. [our pair shredded a lot of pine cones that fell into the nest]
Egg laying in coastal Georgia is late December and early January. Our owl read the book! She laid her first egg on New Year’s Eve and the second three days later. The incubation period ranges from 28 to 37 days, averaging 33. The female alone does all the incubation and rarely moves from the nest, while the male owl captures food and brings it to her, with the first nightly delivery typically soon after dark. [our female seems to leave the eggs for about 15 or 20 minutes sometime around 6:15 or 6:30 each day – we believe she’s feeding on prey brought to her by the male, and that both of them are very close to the nest during this feeding time]
Very cold temperatures are not an issue and eggs have been recorded that survived in the absence of their mother for 10 minutes at below -13F.
Brooding is almost continuous until the offspring are about 2 weeks old, after which it decreases. Great horned owls are tight sitters on the nest and will generally not leave unless pressed.
Typically owls react aggressively to disturbance at the nest and spirited hooting and various strange sounds serve as something of a warning to intruders.
The young weigh around 1.22 oz. at birth on average and can gain more than that each day for the first 4 weeks of life, when they will be more than 2 lbs. They are born with whitish gray down that slowly changes to downy plumage.
Between two weeks and two months, the young develop the ability to defend themselves, grasp food and climb.
They move into nearby branches at 6 weeks and start to fly about a week later. However they are not competent flyers until they are about 10 to 12 weeks old. The age at which they leave the nest is variable based on the abundance of food.
The young birds will stay in the area and most do not fully leave their parents’ territory until right before the parents start to reproduce for the next clutch.
A typical lifespan is 13 years. In general they are most vulnerable in the early stages of life, either from falling from the nest too early or being attacked by crows and ravens, and their mortality rate during their initial dispersal is 50%, with causes that range from human predation to accidents with cars and power lines to secondary poisoning from pest control efforts.
The primary diet of the great horned owl is rats, mice and voles, although it will hunt any animal it can overtake including mid-sized mammals, birds, and reptiles.
Due to its natural-colored plumage, the great horned owl is well camouflaged both while hunting at night and while roosting during the day. Even so they are sometimes spotted by crows. Owls are one of the main predators of crows and their young, and sometimes crows congregate to mob owls and caw angrily at them for hours on end.
Hunting activity tends to peak from dark to midnight and then again in early morning (4:30 a.m.) until sunrise. Owls hunt mainly by watching from a perch until they sense pray and then dive to the ground with their wings folded. They can fly at speeds up to 40 mph in level flight. They can snatch birds directly from tree branches in a glide.
Talons have enormous crushing power (about 28 pounds of force) and the owls generally kill by constriction with the talons holding the prey in place.
Prey are swallowed whole when possible. Six to 10 hours later, the owl will regurgitate pellets of bone, feathers, and other non-digestible bits. Large prey are dismembered. While they are nesting, the owl may stash prey in a nearby roost.
The Great Horned Owl has the most diverse prey of any raptor in this hemisphere – mammals first and foremost, with rabbits a favorite, but also birds, reptiles, amphibians, insects, invertebrates and fish.
A single owl requires between 1.8 and 3.5 oz. of food a day. Due to their poor sense of smell, great horned owls will even attack skunks.
Ear tufts are not ears but feathers; facial disk has a dark rim; bill and talons are gun metal gray. Legs are covered in feathers up to the talons. Females are typically almost a pound larger than males, with a typical weight of 3.5 pound. They are about 2 feet long with a 4-foot wingspan.
Eyes are extremely large relative to size of brain and body, just slightly smaller than the eyes of a human. Visually adapted for nocturnal hunting, the owl has a binocular field of view. Instead of turning its eyes, an owl must turn its whole head and is capable of rotating its neck 270 degrees, in order to see in various directions without moving its entire body.
The owl’s song is normally a low pitched but loud ho-ho-hoo hoo hoo, earning it the familiar name, hoot owl.
Widely distributed in this hemisphere, from the sub Artic to the uplands of Argentina, the great horned owl is very nearly ubiquitous. It prefers areas with open habitats for hunting that are next to woods for roosting and nesting. All mated great horned owls are permanent residents of their territories.
Red tailed hawks and great horned owls have a contentious relationship and try to aggressively exclude each other from their territories. However they can still nest fairly closely when food supplies are ample.
Source: Wikipedia/Great Horned Owl