Even in the dead of winter, nature speaks to us. For the past two months, my wife and I have been charmed by the calls of a most interesting visitor, the Eastern Screech Owl, which has been perching around 78th Street. Every evening at dusk and then between 8:30 and 9 PM, the distinct quiet hoots of this diminutive owl have made me drop what I was reading. I even stopped listening to music on headphones so I could catch the evening nocturne. In 28 years of living here, this is the first time I have heard this owl.
The Eastern Screech Owl (Megascops asio) has the distinction of being one of the most misnamed of birds. Unlike one of its prey items, the Mourning Dove, which does indeed utter a melancholy song, this night predator doesn’t screech at all (unless really agitated). Instead, it offers gentle tremolos or soft calls. Far different from the booming sounds of our region’s larger owls, the Great Horned Owl and the Barred Owl.
If you are used to the image of big fierce- looking owls, you must downsize your search image to spot this one. Adult Eastern Screech Owls are tiny, ranging from 6 to 10 inches long and weighing in at 4-8 ounces. Diminutive birds that are strictly nocturnal in their behavior, they become even harder to see because they are among the best-camouflaged bird species in our region. Eastern Screech Owls sport a dark gray plumage, but the complex patterns and streaks in the feathers allow it to blend with tree bark. They like to nest in abandoned tree cavities where they hole up during the day. But when they do emerge to stand on the cavity’s ledge, pressed against one wall, they disappear visually into the bark. Further south, where pine trees dominate the forest, you can find reddish members of the species. Some birders say this adaptation enables their plumage to merge more successfully with the tawny bark of pine trees or the bright leaves of some deciduous trees, but this is hearsay and not based on genetics. For either color morph, skilled birders rarely spot them, let alone neophytes.
But their presence is typically unmistakable: a weird roll of a song that someone once described as, “Oh-o-o-o-o that I never had been bor-r-r-r-n!” And you can hear them almost anywhere. Females are larger than males as in most owls and have different vocalizations.
Eastern Screech Owls are generalists in habitat selection: deciduous forests, open parklands, forests bordering rivers, even suburban areas such as here in Cabin John. Find a locale with lots of mice and songbirds and they are content. One of their favorite food items is the aforementioned Mourning Dove, which stands no chance against the sharp talons of this little owl. Nor do over 100 other species of birds that have been recorded in their diet. That said, rats and mice make up the bulk of their menu, so they do us homeowners a favor. But they will eat about any small prey item and love crickets, grasshoppers, and other insects, especially during the breeding season. It’s hard to know what drives habitat selection strategies in animals, and discovering those strategies is a major branch of ecology. For this owl in particular, questions emerge: Is it the presence of lots of easy prey to catch, like birds that hang out at backyard feeders, or is it the availability of tree holes for nesting found in older trees, often a scarce resource? Another possibility is that these owls seek out places where larger, predatory owls such as Great Horned Owls and Barred Owls rarely venture, finding roosting spots near houses and in open areas. Perhaps the desire to avoid predators drives habitat selection more than any other factor.
When dusk falls, our owl awakens. Often it hunts from a perch, swooping down to make a kill. Blessed with sharp nocturnal vision and acute hearing, the Eastern Screech Owl is reportedly able to detect the sounds of mice under a blanket of snow. It is in the “swoop” that their extraordinary evolutionary adaptations for night hunting emerge. Their fine hearing is aided by a feature common to owls, something that would look unusual in humans: ears that are asymmetrically placed on the sides of the head (the tufts of feathers that stick up on the top of the head look like ears but are fake). This slight shift enables the owl to compare the differences between each ear’s perception of sound to lock in on an object. The flight feathers are exceptional too: they are serrated at the tips. This built-in noise damper removes the sound of flapping wings, enabling a sneak attack.
My hypothesis is that the screech owl came to visit us and take up temporary residence to move away from dangerous Barred and Great Horned owls now that February, the start of the owl’s breeding season, is upon us (although our neighborhood is full of Cooper’s Hawks, a diurnal raptor also known to go after screech owls). I would have liked to know the motivation for the visits, but I was still so pleased that the owl faithfully called each night and then again before dawn. Sometimes it would even wake us up at night. It had clearly settled in at home in Cabin John.
Then it happened: Radio silence. During the following two weeks, I strained to listen for the songs of our new friend. Night after night, nothing but silence or the annoying sound of a jet plane headed to National Airport. Had I spoken too soon about our backyard being a Barred Owl-free zone? I was walking out in the backyard forest the other day when I saw a large bird with broad wings flap into the same tree our local Eastern Screech Owl had used as its calling perch! A Barred Owl! I hooted at it angrily and it flew away. Two days later my wife thought she heard our friend calling, but it was far away. I thought I had heard it, too. Maybe wishful thinking, a trait of many birders who, eager to see or hear a special bird, can convince themselves they did. I hope he is still around.
The Eastern Screech Owl can live up to 20 years in captivity, but life is much shorter in the wild. Perhaps our friend has moved to Glen Echo for the time being, to visit other families and scour the ground for mice and voles. That is what I like to think, anyway.
By Eric Dinerstein
Illustration By Trudy Nicholson