Great horned owls

Guess “hoooos” back.

A Great Horned owl, with chick. – George Gentry

After 20 years of active birding on the Vineyard, I’ve encountered pretty much all of our regularly occurring bird species, most of our “rare but regular” vagrants, even a few of the outrageous rarities for which the Island is famed. But being an early-to-bed kind of guy, I have managed to miss one of our most dramatic avian residents: the great horned owl.

I fixed this oversight, quite accidentally, when I heard the distinctive hooting of this species in West Tisbury last Saturday night. I was leaving an event at the Nature Conservancy’s Hoft Farm field station off Lambert’s Cove Road. The bird was calling from the tall pitch pines on the hill that is visible from Lambert’s Cove Road.

A great horned owl, surely the same one, was reported there several weeks ago by David Stanwood, who keeps an alert eye (and ear) on the wildlife in that area. The recurring presence of a calling owl there suggests either nesting or an attempt at it; in any case, as with other owls, the hooting of a great horned owl is primarily aimed at staking out territory and attracting a mate.

The story of this species on the Vineyard is somewhat puzzling. Great horned owls were conspicuously absent from the Island for as long as anyone could remember, despite being one of the most common owl species in New England, and one of the most widespread and versatile birds in North America. Their absence here was inexplicable, given that these massive predators nested in respectable numbers just across the water on Cape Cod.

Great horned owls must surely have been here aboriginally. Their breeding range extends northward almost to the end of terra firma in the Arctic, and I can’t believe a bird that hardy wasn’t here in the post-glacial period when rising sea levels separated the Vineyard from the rest of the world some 5,000 years ago. Perhaps European settlers, out of a not-unreasonable belief that these owls preyed on barnyard fowl, wiped them out. If so, it’s still puzzling why the owls went for decades without bothering to recolonize the Vineyard by means of a short flight across the sound.

Which is, presumably, what finally happened about 20 years ago, when a small but evidently persistent population established itself here. Birds have been seen or heard, and nesting either demonstrated or suspected, at locations ranging from Oyster Pond near the south shore to Pilot Hill on the moraine, to Chilmark. I’ve never heard a birder speculate that more than three or four pairs were present here, and the population, if growing, is doing so slowly. Given that these birds like elbow room, their numbers may never grow much beyond what they are now.

Formidable predators, these owls eat pretty much whatever they want. Rabbits and small rodents are typically the mainstay of their diet, but a great horned owl will eat at least the young of species including skunks (owls lack a sense of smell), raccoons, and, yes, domestic dogs and cats. They take birds as well, often bushwhacking roosting victims in the dark.

The beak of a great horned owl is not to be trifled with, powerful enough to pull apart even sizable prey. But it is the talons, or claws, that do the dirty work: A great horned owl typically drops onto its prey from a perch, grabs it by the head, and drives its spikelike talons into the victim’s brain, killing it almost instantly.

While great horned owls have been found nesting in a wide range of situations, the most typical pattern is for them to take over a nest abandoned by some other large bird species. The nest may be in any sort of large tree, though in my experience these owls prefer evergreens, presumably for concealment. It’s not that they have much to fear, but crows, which hate these owls with a passion, will mob any great horned owl they find, and I’m sure that gets annoying.

For years, a pair of red-tailed hawks have nested on the hill where David and I recently heard the great horned owl. I’m trying to think, now, when was the last time I saw those hawks; if they’ve left, died, or been assassinated by an owl, it may be their nest that the owl has occupied.

Great horned owls tolerate human activity quite well, and while they’re primarily nocturnal, it’s not unusual to come across one out hunting at dawn or dusk. Almost two feet long, with a wingspan as great as five feet and a weight of as much as three pounds, this is a species that you cannot confuse with any of our other owls (even if you can’t see the eponymous “horns,” which are actually tufts of feathers). But this bird is most easily detected by its call, a series of deep, resonant hoots that can carry for a mile or more on a quiet night. This sound, once unheard on the Vineyard, appears to have become a permanent part of our nocturnal world.