A great horned owl blends into the bark of a tree with plumage that's a similar pattern and color to the bark. Credit: Courtesy of Bob Duchesne

Owls are spooky. No wonder they have become part of our Halloween traditions.

Many cultures have regarded owls with suspicion and dread, though not all. The Babylonians believed that owls stimulated fertility and protected pregnant women. Early inhabitants of the British Isles thought that if a pregnant woman heard an owl hoot, her child would be blessed. Other early Europeans credited owls with helping spinsters find husbands. The Greeks believed owls to be symbols of good fortune, and they were considered wise. Athena, the Greek goddess of wisdom, often took the form of an owl. Owls were holy symbols in India and Japan.

The Romans, however, came to fear owls as omens of impending doom. They believed that hooting owls foretold military defeat, shipwrecks and the deaths of emperors, including Julius and Augustus Caesar. Their recommended remedy was to kill the offending owl and nail it to the front door, if you could catch it. That myth persisted in parts of Britain until the 1800s.

Native American cultures developed a wealth of folklore about owls, differing widely across the continent. Many tribes thought they brought sickness and death. Some believed they were protective spirits, and a few tribes considered them to be the earthly form of gods. One thing is for certain: virtually no culture in history has been neutral about owls.

Owls have often been perceived as messengers, even accompanying the souls of the dead to the afterlife. The owl-as-messenger took on new life in Harry Potter, as Hogwarts students had their own personal owls who delivered mail and ran errands. Harry’s owl, Hedwig, was a snowy owl, but many species of owls were featured in the story.

Owl folklore and myths have some basis in fact. Owls possess a number of spooky attributes. Foremost, they are silent killers. Their large wings allow them to fly slowly, with less noise. The leading edges of owl wings have comb-like serrations that break up the airflow in front, eliminating the “whoosh” sound of wingbeats. The trailing edges have downy featherings that muffle what little noise is left. Owls’ prey rarely hear them coming.

Owls have offset ears. One ear is higher on the head than the other. The miniscule difference allows the owl to locate prey by noise, as sound waves reach each ear at slightly different times. Large facial disks further funnel sound to the ears.

Most owls are nocturnal, so humans usually encounter them at night. Historically, many cultures have feared things that go bump in the night. Some owls, mostly of the far north, hunt in daylight. After all, they live in the land of the midnight sun. Snowy owls are white, like their hoary, treeless habitats in the tundra and they are faster than most owls, able to chase down prey.

Owls are cryptically colored — various shades of brown and gray — in a pattern that matches the bark of the trees they sit in. Even a large owl can blend into the background when sitting stationary in a tree. Imagine how many humans over the past 10,000 years have been shocked to suddenly notice an owl watching them from a nearby perch.

This cryptic coloration even figures into owl mating. Like most nocturnal critters, owl eyes are big and loaded with rods, which gather light in dim conditions. This comes at the sacrifice of cones that would allow them to distinguish colors. Thus, owls are not adorned with bright plumage, because they are functionally color blind. However, owl plumage does contain an unusual class of pigments, which react to ultraviolet light in ways that only owls can see. Though invisible to us, these shades apparently signal age and mating suitability to other owls.

Owls aren’t terribly fond of human presence, but they are fond of the rodents that hang around people. So our species has a long history of bumping into theirs in somewhat spooky fashion. Barred owls are the most frequently seen and heard owls in Maine, occupying the forest edges all around us. Great horned owls seem to like cemeteries and currently nest in Bangor’s Mount Hope Cemetery. Elsewhere, barn owls really do nest in barns. Eastern screech owls are cavity-nesters in urban and suburban backyards.

Harry Potter notwithstanding, real owls make poor pets. They are stubborn, resistant to training and not all that bright. In addition, it is illegal to own one in most parts of the world. Plus, since they are nocturnal and noisier at night, they will haunt your dreams. Spooky.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.