April 23, 2020
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Ohio's Owls was originally published in the BFEC Newsletter, Vol. 14/No. 1, Winter 2010.
Through the centuries and across the globe, owls have in turns been the subject of our reverence and our fear. They have been considered “omens of good luck, bad fortune, impending doom, wisdom, foolishness, evil and witchcraft, and even predictors of weather” (ODNR Division of Wildlife). Clearly, their appearance and habits provide plenty to fuel the imagination.
Owls are in their element at night, at a time when humans generally feel more vulnerable. Their calls ring through the darkness, their vision enhanced with those enormous, staring eyes. They hone in on sights and sounds even further by swiveling their heads almost 360 degrees.
In human terms, this would signal the moment to call in the exorcist. Eerie? Yes. But these traits are examples of incredible adaptations that make owls very good at what they do — hunt.
Their neck flexibility, for example, is a function of thirteen neck vertebrate, compared with human’s mere seven.
Those enormous eyes can encompass up to five percent of the bird’s overall mass, and allows them to more efficiently collect and process light in dim conditions. If our eyes were proportionately as large, they would be the size of softballs.
With the exceptional tools of a predator, owls make great neighbors for anyone with an unwelcomed mouse population. Of the twelve owl species that have been recorded in Ohio, the barn owl has one of the best reputations as a “mouser.”
Barn owls have probably done much to perpetuate superstition due to their stark, white face and almost completely nocturnal habits, flying well after dusk. They are also very adaptable to people and their structures, indeed preferring to nest in barns or vacant houses.
Barn owls primarily eat mice and voles that populate “old field” habitat, or fallow farm fields that have grown up in grasses and flowering plants. Their pre-settlement population in Ohio was probably fairly small given that forests dominated the landscape. But as forests gave way to farms, the barn owl population grew.
Their fate again took a turn, however, as farm practices changed and large tracts of old field habitat shrank. Near 1990 barn owl populations hit a low point, with only a dozen or so nesting pairs estimated statewide.
Programs that encourage the placement of nesting boxes in barns have been credited in part with a modest recovery. There are now estimated to be 50 nesting pairs in the state, two of which have been confirmed in Knox County.
Owls may seem elusive, but you can increase your chances by learning a little bit about their habits, and thus when and where to look. As with many animals, it’s helpful to look for clues before finding the animals themselves.
Evidence may come, for example, in the form of an incessantly cawing murder (or flock) of crows. Sometimes crows seem to get together and make a lot of noise just for the heck of it, but at other times they are more purposeful and take to “mobbing” owls. Crows are well known for this behavior, but song birds will also mob smaller birds of prey. The next time you hear an cacophonous band of crows, look up to see if they are busy harassing an owl.
The ground is another place to look for a not so glamorous animal sign - scat. Owls leave a somewhat different marker when they regurgitate “pellets,” or balls of indigestible fur and bones, after a meal. A collection of pellets under a tree may indicate a favorite roosting (or day time resting) site of an owl, such as a dense stand of pine or spruce.
Many species of owls start nesting in late winter, which is a good time to listen for their nocturnal calls. The convenient lack of leaves in this season also makes them easier to spot, especially considering the hours they spend sitting in a predictable location and flying back and forth to feed mates or young.
Great horned owls are one of Ohio’s largest and earliest nesting birds, starting in January or February. They usually use old nests of other animals such as hawk or squirrels. Look for their large, tufted ears sticking out above the edge. Keeping an eye on tree cavities may also lead to an owl spotting, especially of the smaller screech and barred owls.
Of the twelve owl species recorded in Ohio, the four with breeding populations are shown below.
Ohio's largest resident owl, two feet tall with five food wingspan. Ear tuft "horns" are not related to hearing, but rather for visual effect.
Habitat: Very adaptable; farmland with small wood lots, suburban parks. Nests very early in late January.
Diet: Great variety of muskrats, skunks, squirrels, etc.
Distinguished by its eight inch stature, prominent ear tufts and large yellow eyes. Named for its song, an eerie, trembling wail and soft trill.
Habitat: Towns, orchards and small woodlots. Nests in nature cavities (like hollow trees), without any nesting material.
Diet: Mice, large insects, frogs, snakes.
Named for horizontal bars of white and brown on neck and chest. Eyes are brown. Distinctive call that sounds like the phrase "who cooks for you?"
Habitat: River bottoms, large tracts of forests.
Diet: Small rodents are preferred, but will eat other mammals and insects.
Once common, now on the Ohio threatened species list. Stands a little over a foot tall with a wingspan of up to four feet. Notably long legs.
Habitat: Old fields and grasslands; nests in barns and vacant buildings in March through May, usual clutch size of five.
Diet: Mice and voles.
In some species, asymmetrical ear placement helps owls hone in on sound. The brains of these species can process a 20 millionths of a second difference between a sound's arrival at each ear.
While humans must keep their muscles contracted when holding an object, owls have what is essentially a mechanical locking device that allows them to grasp an object with full force without continuous, conscious muscle contractions.
Most owls lay 3-5 eggs, though not at the same time — they are laid, and hatch a day or two apart. Older, larger owlets may get more food from parents, and younger owlets often do not survive unless food is very plentiful. This strategy ensures that some will survive even when food is scarce, rather than all owlets starving.
As they near maturity, young barn owls will eat the equivalent of a dozen mice per night. The Owl Rehabilitation Research Foundation, Ontario, Canada, reports that barn owls consume twice as much food for their weight as other owls.