Sunday, April 11, 2021

Barn Owls: The Ghostly Rodent Destroyer

Barn OwlHow do you describe Barn Owls? To begin with, what birds are stranger than owls? The oddly inelegant shape, the seemingly humorless and serious demeanor, the hostile and insistent beak snapping, the strength all out of proportion to their sizes?

And then there is the barn owl, with that heart shaped, almost alien, face, the head wagging when surprised or threatened, the long, gawky legs, and that arrestingly loud, drawn out and raspy hiss, like a cobra with a microphone.

Barn owls are a weird and fascinating species, even within the ghostliest of raptor orders, Strigiformes. The Martians have landed, and they have come for your rodents! In an interesting observation, the Carolina Raptor Center, speculating on the origin of ghosts and goblins in people’s minds, and mindful of the link between old barns, church steeples and agricultural fields, in other words, the proximity of villages to barn owl nesting sites, wonder whether the ghostly appearance, odd hisses, screeches and screams of the barn owl, helped foster such nightmares.


Barn owls are the most widely distributed of all raptors, found on every continent but Antarctica. Alas, barn owls, and other members of the family Tytonidae, seem more delicate than members of the “true owl” family, Strigidae, with most dying during their first year, and with the average age in the wild of only 18 months. Wesley, the hero of Stacey O’Brien’s book about her barn owl, lived to be 20, so once again, when you add a steady food supply, observation, and care to a wild animal, it dramatically increases their life span. Mature barn owls are just under a pound, and about 15 to 20 inches from beak to tail. As with all raptors, the females are larger than the males, and have a slightly more reddish golden-brown breast than the males, with more prominent spots. Barn owls have wing spans from 36 to 48 inches. Great Horned Owls take a discouragingly high proportion of barn owls and are sometimes suspected of patiently perching near barn owl nest sites to grab branchers and fledglings. Other mortality factors are what you would expect: vehicles, pesticide poisoning, being shot, high power lines, etc.

barn owl

Steve with Barn Owl by John Vant Erve, provided by Adirondack Wildlife Refuge

Barn owls are rodent-eating machines, and, as many farmers are rediscovering, safer and more effective than rodenticides, as they kill only the targeted animals. A mating pair of barn owls raising five owlets, may take 3,000 rodents in a year, and since barn owls seem to breed in response to the rodent supply, they may breed multiple times in any given year. In addition, barn owls are less territorial than other raptors, so, as Tom Hoffman points out at Barn Owl Headquarters, the farmer may have set up six barn owl nesting boxes within a 100-acre field. While most of what barn owls take are small rodents, according to BarnOwlBox, barn owls have displayed a versatility in hunting various types of prey, focusing on pocket gophers in California wine country, bats in Austria, red wing blackbirds in parts of the Midwest, house mice in Spain, and have even been seen catching fish. Is anything safe?!

As with the Great Horned Owl, a consideration of the barn owl’s offensive weapons, along with their tools for detecting prey, lead to the conclusion that life is definitely not fair for the rodents they prey on.  The barn owl seeks his prey, by flying in a side-to-side pattern, about ten feet off the ground, with the legs swaying left and right, while sweeping a narrow swath of ground. Sometimes they will hunt from a perch, gliding down to seize rodents.

As with other owls, the barn owl’s eyes are locked into the skull sockets in such a way, that the owl must swivel the head to change its field of vision. Like people, owls have binocular vision, while other raptors’ eyes are located on either side of the face. A barn owl’s eyes are twice as efficient as ours in dim light and are better at discerning outlines. Like a boxer slipping punches, barn owls bob their head when reacting to movement in their immediate vicinity. Some say this is done to improve depth perception.

Barn owl

Photo by Kevin MacKenzie, provided by Adirondack Wildlife Refuge

A barn owl’s hearing is anywhere from 25 to 100 times more sensitive than ours. The ears are asymmetrical, with one set high on the right, and the other in an inverted position low on the left just inside and under the heart-shaped facial disk, whose outline is formed by stiff, bristly tan feathers, and which acts as a dish for collecting sound. When sound reaches the lower ear, the barn owl swivels the head through its lateral and medial axis, until the sound is hitting both ears simultaneously, and, because the eyes can only look straight forward, by definition, the owl is staring at the location of the sound’s source. Laboratory tests indicate that blindfolded barn owls can catch mice, using their hearing alone, and can not only locate a mouse by the sound of its heartbeat, but can audibly discern the movements of one type of prey from another.

Soft and light feathers enable silent flight, by breaking the air disturbance of the wings, into thousands of tiny pockets of turbulence, inaudible to the ears of mammals. This not only prevents the prey from hearing the owl’s approach but allows the owl to continue triangulating the prey’s location as they approach. The outer toe swings back and forth, to enable perching with three toes in front, and the rear toe, or hallux, in the rear, or, when striking prey, to swing back and join the hallux, in framing the rodent’s spine, leading to a firm grip, allowing an easier kill by the beak. As the owl reaches its unsuspecting prey, the legs extend the open talons forward, the head draws back and the eyes shut, as the talons grasp the prey. If the prey is not killed by the crush of the talons, the beak is used to quickly finish the job.

barn owl chick

4 week old fledge by Trish Marki, provided by Adirondack Wildlife Refuge

Female barn owls can brood when they are a year old. Like most owls, barn owls do not construct nests, but appropriate any suitable cavity, natural or man made, where the female lays 3 to 12 eggs, in intervals of 2 to 3 days.  Incubation lasts about 33 days for each egg, and the owlets fledge at between 56 and 62 days. Mom broods while Dad hunts and provides food for Mom and the growing owlets.

It is not unusual during the nesting season, to find owlets on the ground in the vicinity of the nest. Before “rescuing” this comically hostile ball of feathers, observe the owl over a few days, just to confirm that the parents are not feeding it where it sits. If the vertical “keel” of a bird’s breastbone feels sharp, and protrudes out from the attached muscles, it is often a sign of starvation, in which case it means the young owl is not being fed, and it is time to call the rehabber. The young owl may be a brancher who tumbled from its perch in its first attempt at flight, or was booted by an older unsentimental sibling, as a strategy for garnering a higher portion of the food Mom and Dad bring back to the nest. Each Summer, some of our education birds, notably the Great Horned and Barred owls, foster-parent fledglings, who are later released in early Fall.

 

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Steve Hall

Steve and Wendy Hall run the Adirondack Wildlife Refuge and Rehab Center in Wilmington. They've been rehabbing and releasing wild animals for over 45 years, specialize in predators, keep wolves as the cornerstone of their educational program, and have lived in the Adirondacks for the past 20 years. The Adirondack Wildlife Refuge became a non-profit about 10 years ago.

Visit www.AdirondackWildlife.org to learn more.


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3 Responses

  1. Julian Shepherd says:

    Steve, Nice article on one of my favorites – thanks. Can’t resist telling you about an experiment, which maybe you know, that I tell my students as an elegantly simple experiment to show that barn owls can catch prey totally by ear in total darkness. In his pioneering work in the late 1950s, Roger Payne worked in an old shack near Cornell illuminated only with infrared light, and photographed barn owls catching prey. After first finding that barn owls could catch a mouse moving over a noisy floor in total darkness, he tied a leaf to a mouse’s tail and caught the owl pouncing on the noisy leaf as the mouse moved over a soft rubber floor.

  2. Thanks Julian. We’ve had barn owls at the Wildlife Refuge, and I’ve been thinking about them for some time. I wrote an earlier version of this article for our web site, and while researching, I came across references to tests like these, but the leaf adds an interesting twist..

  3. Lillian says:

    Thank you so much for this! We had the great privilege of having a beautiful barred owl perced on our patio perimeter three different days. No work got done while watching for hours, but would not trade the experience…

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