Working the Night Shift
Who’s awake? Me too! Who’s awake? Me too! In the fall and winter, this series of five rhythmic, muffled, slightly eerie hoots—all on one pitch—increasingly wafts through the darkness. The sentinel taking attendance is the Great Horned Owl. Measuring nearly two feet from head to tail, the Great Horned is the largest and most widely distributed owl in North America. Seen most commonly perched upright in trees or on power poles at dusk, this owl is heavily barred in brown and black. Feather tufts (not horns at all) atop its large head give rise to its rather inaccurate, albeit catchy, common name. Its enormous yellow eyes are so large that they cannot move in the owl’s head. However, the owl can swivel its head as much as 270 degrees to look in any direction. Since Great Horneds hunt at night, locating prey by sound is vital—and this owl has the requisite acute hearing. With a skull nearly as wide as its body, its ears are set relatively far apart and offset from each other a bit, allowing the raptor to triangulate the location of the tiniest sounds even more accurately. Its large and wickedly strong talons allow it to instantly snap the spine of even large prey. As with many birds of prey, both males and females look the same, although females often are as much as 30% heavier.
No other owl in North America makes use of as many diverse habitats as does this massive, powerful raptor. Since Great Horneds hunt from high perches, pretty much all they need are a few trees, some open areas for hunting, and an abundance of prey. As a result, Great Horneds can be found in San Diego County from the coast up to the mountains and down to the floor of Anza-Borrego Desert. As is true with most owls, first on the menu are rodents, rodents, rodents (e.g., mice, rats, voles) followed by other nocturnal (active at night) and crepuscular (active at dawn and dusk) mammals such as skunks and rabbits. Great Horneds have even been known to take on porcupines, although neither in that fight typically comes out very well. Great Horneds will also capture birds as large as ducks or geese, snakes, lizards, and sometimes even insects. As is true with most raptors, owls swallow their prey—bones, hair, tails, feet, feathers, teeth—whole. An owl’s stomach has two parts—the proventriculus and the ventriculus—that separate and compress all of the indigestible parts of its food into a pellet, which it then egests or “casts”—fancy words for “throws up.” Although the biology is a bit different, the process is not unlike a cat’s coughing up a hairball.
Great Horneds don’t build their own nests but instead use old stick nests built by large birds such as a Common Raven or a Red-tailed or Red-shouldered Hawk. One surefire way to find a Great Horned’s nest is to look for bulky stick nests in large leafless trees of winter. Every now and then, you might spot what looks like a nest with ears. That’ll be the female, hunkered down with just the top of her head showing, keeping the kids safe.
Great Horneds begin nesting very early in the year, typically in January or February. Nesting so early involves considerable risk. Eggs must continually be kept warm and dry during the entire 28 – 35 days before hatching, which can be a real challenge when temperatures in the mountains may plummet or rains may fall heavily. Owlets require four or five weeks to mature once they hatch, so they need extra time not only to fledge but also to develop complex hunting skills once they fledge. By hatching in late winter, the owlets are ready to start practicing those skills at a time when lots of other birds and mammals start raising young, providing an abundance of prey for practice.
But Great Horned Owls are not the only owls breeding this time of year. Several other owls of San Diego County—e.g., Barn Owl, Western Screech-Owl, Long-Eared Owl—also begin their breeding seasons this time of year.
In some American Indian cultures, the owl embodies sinister or evil happenings. Even in mainstream western culture, this creature often suggests mystery or trouble. Who remembers the various references and appearances of Great Horned Owls in the 1990s television series Twin Peaks? (“The owls are not what they seem…” Never a good omen in that show.) In reality, though, all owls deserves our respect and deep appreciation. Without the keen skills of these vigilant nocturnal hunters, the rodent population might now be running the world while we sleep. Who’s awake, indeed…