Great Horned Owls do not build their own nests, though they may provide some lining to an existing cavity or nest. Snags, cliffs and man-made structures provide nesting sites, but most commonly Great Horned Owls use the tree nests of other species such as hawks (especially Red-tailed) crows, ravens and squirrels. Most, but not all, nests are used for only one season. Pictured is a Great Blue Heron nest that has been usurped by a Great Horned Owl family – a feat achieved by the owls claiming the nest as early as February, prior to the return of herons.
After incubating her eggs for roughly a month, the female Great Horned Owl then broods her young for two to three weeks. The father’s role consists of bringing food to the female while she is incubating and brooding. She then tears the food up into bite-size pieces for the nestlings.
When the nestlings no longer need the heat their mother’s body provides, brooding ends but the mother stays with her nestlings until they fledge at about seven weeks of age. (Pictured: Great Horned Owl mother and two downy nestlings, roughly six weeks old. Thanks to Marc Beerman for photo op.)
Shortly after being fed, most songbird nestlings produce what is called a fecal sac – a mucous membrane (usually white with a dark end) that contains their excrement. This sac enables easy removal of the chicks’ waste by the parents. In an effort to keep its young healthy and to reduce the chances of predators finding the nest, the parent takes the fecal sac in its beak, flies away and discards it some distance from the nest.
Some nestlings, including those of Warbling Vireos, are extremely cooperative when it comes to assisting their parents in keeping the nest clean. Just prior to producing a fecal sac they position themselves with their rear ends up in the air (see photo), where their parents can easily procure the fecal sacs when they appear.
In the Northeast, Bald Eagle eggs are hatching and the heads of the one-to-three chicks can be seen bobbing up and down, anxiously begging for a tidbit of food from one of their parents. For the first two or three weeks, their mother stays with them 90 percent of the time, keeping them warm and tearing food brought by their father into little pieces that she feeds to her chicks. Eventually food-gathering is shared equally between the parents, and is usually sufficient to produce a weight gain of 3 ½ ounces a day for male chicks, and 4 ½ ounces per day for the female chicks. (Female raptors are typically larger than the males.) The chicks in these photos are approximately two weeks old and are covered with their darker, second coat of down, which comes in when they are a little over a week old.
Young Barred Owls are fed by their parents from the day they hatch until late summer/early fall. During their first two weeks, food is delivered by the adult male to the adult female, in a bill-to-bill exchange. The female tears up the prey into swallowable bits and feeds them to her offspring. During this time the female does little hunting, but she begins to capture prey after about two weeks of brooding the young. At about this time, the young begin consuming whole prey on their own (see photo). Female prey deliveries are greatest immediately following sunset and immediately prior to sunrise, while male prey deliveries remain fairly constant throughout the night. (Photo: Barred Owl delivering Red-backed Vole to nestling.) (Thanks to Alfred Balch for photo op.)
When eagle chicks hatch they are covered with light gray down and have brown eyes and pink legs. One parent, usually the female, spends most of the day in the nest with her young for the first three weeks, brooding and keeping them warm. The male provides most of the food during this time. After he delivers prey, she tears off small pieces and feeds them to the nestlings. The chicks gain weight rapidly – roughly ¼ pound a day – so that in three or four short weeks the young are nearly the size of an adult. Eaglets are roughly six weeks old before they are capable of tearing off food and feeding themselves, and at least eight weeks old before they leave the nest. (Note corn stalk that’s been incorporated into nest; photo: one-week-old eaglet & its mother)
In the Northeast, Bald Eagles seek out the tallest trees around in which to build their nests. In certain locations in Alaska, coastal California and northern Canada where there are no trees, Bald Eagles will nest on the ground. When building a nest in a tree, eagles will usually build it in the top quarter of the tree, just below the crown, on limbs capable of supporting a large nest. Sticks from the ground are collected up to a mile away from the nest or are broken off of nearby trees. Additional materials are regularly added to the nest throughout the year, including daily additions during the breeding season (see photo).
Many live eagle cams can be found online (in Minnesota, one chick, one egg – http://mnbound.com/live-eagle-cam/ ; in Georgia, older nestlings: http://www.berry.edu/eaglecam/ ; in Pennsylvania, very young chicks: http://www.ustream.tv/decoraheagles ), giving the viewer a window into the incubation, birth and growth of these raptors. Depending on the location of the nest, one can see every stage of development, from eggs to hatchlings to all-but-fledged nestlings. In New England, eggs are soon to hatch, if they haven’t already. (Thanks to Marianne Blake for photo op.)
Great Horned Owls are said to have the widest range of nest sites of any bird in North or South America. Like other owls and falcons, this raptor does not build its own nest, but rather relies heavily on abandoned stick nests of diurnal birds of prey. Red-tailed Hawk nests are often usurped, as well as those of Bald Eagles, crows, ravens and herons. Nests may be lined with shreds of bark, leaves, downy feathers from the owl’s breast, fur of prey and trampled pellets. In addition to bird nests, Great Horned Owls also raise their one to four nestlings (usually two) in tree cavities and snags, on cliffs, in deserted buildings, in squirrel nests and even on the ground.
The female Great Horned Owl does all the incubating; the male delivers prey to her at intervals throughout the night. These early nesters have incubated eggs successfully when outside temperatures have been as low as -27°F. Hopefully warmer temperatures will welcome the newly hatched owlets in about a month. (photo: mostly hidden Great Horned Owl in Great Blue Heron nest)