By Rick Borchelt
Here in the D.C. metro area, we’re accustomed to having the icy stillness of midwinter nights being broken by rambunctious college parties, sirens and traffic helicopters. But there’s another night sound that lucky locals can hear in winter: the courtship duets of our two large resident owl species, the great horned owl (Bubo virginianus) and the barred owl (Strix varia). These birds can be quite noisy, too!
When they aren’t hunting in the cold nights, males of these owl species court females with an impressive variety of hoots, screeches, barks, and screams (you can sample some here: tinyurl.com/ms6paf8h). These sounds are a prelude to mating, establishing a nest and incubating eggs — all which take place through the dead of winter. Both owl species are surprisingly common wherever sizable stands of mature trees are found; both regularly nest in and around College Park and our sister suburbs.
Great horned owls and barred owls are the region’s largest resident owls (in our area, only snowy owls, our occasional winter visitors, are larger). Barred owls are about three-quarters the size of great horned owls and have correspondingly smaller feet that only allow them to take small food — squirrels, rabbits, mice, voles and rats, along with frogs and salamanders. (They’re so agile and dexterous that they can even capture large moths and other night insects with their feet.) Great horned owls hunt rodents and rabbits, too, and can also handle larger prey like opossums and the occasional unmonitored chihuahua or free-range cat. They’re one of the few predators that regularly feeds on skunks.
The winter owl concert season kicks off in December, with great horned owls calling through the night, often from tall pines and other evergreens. The deep bass hoots, “hoo-h’Hoo-hoo-hoo,” belong to the male, while the female’s responses are a little higher and a little raspier. Great horned owl calls are mostly all on the same pitch, which will help differentiate them from the calls of barred owls. Male and female great horned owls duet together for a month or more before claiming a nest site in late January and settling down. Both of these owl species mate for life.
Great horned owls nest in an astonishing range of sites — sheds, attics of empty houses and hollow trees, for example. More often, they commandeer an existing crow, hawk, heron or osprey nest. If you spot an old nest of these other birds in January, don’t be surprised to find the head tufts of a female owl sticking up over the nest rim as she incubates her clutch of eggs.
Great horned owls do little to spruce up a nest, be it an old one they’ve claimed or a new one they’ve made themselves. At best, a female owl might add a few lichens or bits of moss before laying two to four creamy white eggs. She then incubates her eggs through the ice and snow of late winter while her partner does the hunting and provides her with food, since she cannot leave the eggs while the weather is so cold. The eggs hatch after about five weeks, typically in March.
Barred owls don’t usually ramp up their duets until January. Their most common call is four or five baritone notes that jump up and down in pitch, “who-cooks’-for-you’, who-cooks’-for-you-all.” Sometimes the call is just two notes, a very military “hoo’-ah.”
Barred owls usually pick for their nest site a tree hole or cavity, or the top of a dead tree snag. The female lays two to three white eggs, which she incubates by herself in late winter while the male hunts for her. Barred owl eggs hatch in about 28 days.
Both barred and great horned owls need to get an early start on mating and nesting because their young are slow to develop. They typically fledge from the nest in May, when they’re about two months old, and adults continue to feed them and teach them to hunt through the summer and early fall. While the chicks of most birds are born naked, these owl chicks hatch with a thick, fuzzy down coat that helps protect them from freezing in the deep winter cold — and frequently earns them top marks in the cutest birds category.
Great horned owls are the apex predators in the bird world that everyone else fears. Great horned owls regularly take roosting or nestling herons and have even been known to snatch eaglets and young ospreys from their nests. They will also take young — and sometimes even adult — barred owls; if you have a great horned owl pair in your neighborhood, barred owls will clear out.
Great horned owls are ubiquitous across the U. S.; their range extends north into Canada and well into South America. They have such a large breeding range in part because they adapt well to drier upland habitats and a broad range of nesting sites. Barred owls, by contrast, need large trees for nest sites. Their historic range was limited to the eastern U.S., but fire suppression and tree planting across the Great Plains have allowed barred owls to hop-scotch along rivers across the prairies and into the old growth forests of the Northwest, where they now give the endangered spotted owl serious competition.
Have questions for Rick about the world of nature in and around the city, or suggestions for future ”College Park Wild” columns? Drop him a note at email@example.com.