For the past six winters a Barred Owl has been a daily visitor at my house. For most of these years, he roosted (and slept) all day every day from December through February on a White Birch tree just outside my door. Although I usually try not to interfere with the natural rhythm of things, one year when the snow was exceptionally deep, making hunting quite challenging, I decided to offer the owl a daily treat – one small rodent. Enough to entice him but not to satiate him or make him dependent upon this source of food. (I once opened up the gizzard of a road-killed Barred Owl and discovered five small rodents – they average about this amount per day.) Thanks to the Listserv in my town, I could appeal to residents for small rodents (trapped, not poisoned) which they generously deposited in a specially marked box outside the Town Hall, freshly frozen.
Every afternoon like clockwork the Barred Owl would become alert and open his eyes. If he had left his perch during the day, he would return at dusk, precisely at 4:30 p.m. His timing appeared to be in sync with the amount of daylight, as he arrived a bit later as the days lengthened. Most mornings I would take a mouse from the freezer and let it thaw (when I forgot, the microwave came in handy!). I would take the mouse outside, dangle it by its tail to alert the observing owl, and place it on the railing of my porch. Practically before my hand released the mouse the owl would fly in, grasp the mouse on the fly in its talons and disappear into the woods. More than once I felt the tips of his wings brush against me.
Six years, 60 days a year, comes to 360 days…this owl has spent nearly a year, one-tenth of its life, outside my door. I came upon the remains of a Barred Owl not even a quarter of a mile from my house this week. I can only hope it wasn’t my friend.
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Over the past few weeks many people in northern New England have discovered Barred Owls perching near their bird feeders during the day. At this time of year, with snow on the ground, food is harder to find and owls are forced to hunt during the day as well as at night. Bird feeders are a sure source of food, as mice and voles are coming out to feed on spilled seed (most often at night).
The owls we see are relying primarily on their sense of hearing to locate small rodents. Their ear openings are asymmetrically placed, which means that sounds reach the owl’s ears at different times. This helps them zero in on the exact location where the sound is coming from, both when they are perched as well as in flight.
Although Barred Owls can detect the sound of a mouse scurrying through tunnels two feet beneath the snow, this winter has been more challenging for them than many. Almost every snow storm has been followed by rain, which has created multiple layers of icy crust. Although sound may be heard through solid, liquid, or gaseous matter, one wonders if these multiple layers of crust compromise an owl’s ability to hear. In addition, these conditions can’t help but impede an owl’s ability to reach its target as quickly as it normally does.
A dear friend whose compassion for creatures big and small is unmatched was going to great lengths (coating balls of hamburger with hair cut from her dog’s coat so they would bear some resemblance to small rodents) to help a resident owl in a time of need. Some would argue that nature shouldn’t be interfered with, but those readers with a desire to come to the aid of a hungry owl could let a little seed fall on the snow that’s packed down around the feeder in hopes that a large supply of accessible food might attract more rodents which might fill more owl stomachs.
Most owls do not bother to tear small prey such as mice and voles apart but instead swallow them whole. After eight to sixteen hours, all the nutrients available in the eaten prey have been absorbed by the bird. Owls cannot digest the fur, feathers, bones, teeth and nails of their prey, so these parts remain in the bird’s gizzard (specialized organ that grinds up food in most birds but serves as a filter for holding indigestible parts in birds of prey). This accumulation of indigestible parts takes on its pellet form (which is the shape of the gizzard) about eight hours after ingestion, but is sometimes retained by the owl for another six hours or so before being coughed up. As a rule, bones are on the inside of the pellet, and the fur and feathers form a soft coating on the outside.
The stored pellet partially blocks the entrance to the digestive system so it must be ejected before the owl can eat again. This process takes anywhere from a few seconds to several minutes. The owl appears to “yawn” several times before regurgitating the pellet. Note that the pictured Barred Owl has prey (a Deer or White-footed Mouse) in its talons, but out of necessity is getting rid of a pellet before devouring it.
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If you heard Barred Owls calling this winter, and have occasionally spotted one in the same vicinity this spring, now is the time to start looking up at the canopy to see if they produced any young owls. Having spent four or five weeks in a tree cavity being fed and cared for by their parents, Barred Owl nestlings get the urge to spread their talons (and eventually their wings) and leave their nest about this time of year. It will be roughly another month before they begin short flights; until then the fledglings are referred to as “branchers,” as that is where you will find them, perched and begging for food from their parents, who will continue to feed them until late summer or fall. (If you know a youngster who is captivated by owls, they might enjoy reading Otis the Owl by yours truly!)
With snow on the ground, the season of stories in the snow has begun. Many of the animals that remain active in New England during the winter are nocturnal so we rarely get a glimpse of them. But, more than at any other time of year, we are privilege to their activities due to the tracks and traces they leave in and on the snow during the night.
Much information can be gathered from these signs. Often at a kill site, the identity of the predator as well as the prey can be determined by shape, form or measurement. One can see from this photograph that a bird of prey (measurements indicate a barred owl) swooped down on a small rodent (judging from tracks, probably a meadow vole) and was successful in capturing it.
Even though a kill scene such as this, or any other wildlife activity recorded in the snow, may reveal the probable identity of the characters in the story, there are always more questions than answers, which is what gets us out in this frigid weather, day after day. The main question I’m left with after viewing this scene is why do voles and mice risk their lives by travelling on the surface of the snow at times, when they just as well could have covered the same ground in the maze of tunnels they’ve created deep in the subnivean layer between the ground and the snow (where they would be out of sight of hungry predators)? (Thanks to Rob Foote for photo.)
Unlike most young birds, Barred Owls fledge before they can fly. On average, they leave their nest when they are around eight weeks old, and don’t master flight until they’re about 12 weeks old. Fledging for a Barred Owl consists of climbing up out of the tree cavity where they spent their first two months, onto a nearby limb where its parents will tend to it. More often than not there is a nearby branch which it can hop to.
In the fledging depicted, the closest limb was a good 10-15 feet above the nesting cavity. With the help of its strong talons, beak and wings, the fledgling managed to scale the tree trunk up to a somewhat horizontal stub where it could get a good purchase. It may not have been the most graceful ascension, but the fact that it could manage to climb straight up for this distance without the assistance of any grasping fingers was impressive, to say the least. Fledged Barred Owls continue to be fed by their parents until they can fly and capture their own prey. (Photo: Barred Owl chick fledging – clockwise, starting from upper left)
For about a month the female Barred Owl sits on her 1-5 eggs (usually 2 or 3) until her white, downy chicks hatch, usually around the end of April or beginning of May. At about two weeks (mid-May) their natal down is being replaced by a white-tipped gray-buff secondary down, and primary feathers are beginning to grow in. They remain in their cavity nest for their first month.
It is pretty safe to assume that the adult owl in this photograph is a female as she is in constant attendance during the chicks’ first two weeks. The male brings her food which she tears into little bits so the chicks can swallow it. At the beginning of the third week, the female begins leaving the nest frequently to hunt. When she is at the nest, she often takes breaks from the kids and sits at the entrance surveying her surroundings. At this point the chicks start consuming prey (that is delivered to them) on their own. In a week or two the chicks will also start appearing at the cavity entrance. By their fourth or fifth week, the still-flightless chicks will leave the nest, but parental provision of food continues until fall.
Using their keen eyesight and sense of hearing, Barred Owls typically sit and perch on a branch, surveying the ground beneath them for whatever morsel appears, small mammals and birds being at the top of their list during the winter, with more emphasis on amphibians, reptiles, fish and invertebrates during the warmer months.
Several times I have observed a Barred Owl taking advantage of a vernal pool that was teaming with life, specifically Wood Frogs and Spring Peepers. Perched in a nearby tree, the owl kept an eye out for any sign of movement in the water. When ripples appeared near the shore it would swoop down to the water’s edge in an attempt to grasp a frog with its talons. Although it met with repeated failure, success was inevitable due to the plethora of distracted mating frogs.
Because they lack hair and feathers, frogs may be underestimated when scientists dissect owl pellets to see what Barred Owls eat. Given the frequency with which I have observed these feathered fishermen, I would think that might be very likely.
There are roughly 85 species of North American birds that are cavity nesters – birds that excavate nesting holes, use cavities resulting from decay (natural cavities), or use holes created by other species in dead or deteriorating trees. Many of them get a jump start on open-nesting birds, due to added protection from the elements. Barred owls, titmice, chickadees, wood ducks, woodpeckers, bluebirds, mergansers – many have chosen a nest site and are busy excavating, lining a cavity or laying eggs long before many other species have even returned to their breeding grounds.
The reduced risk of predation a cavity nest experiences is reflected in several ways: many cavity-nesters have larger clutches of eggs than open-nesting birds and cavity-nesting young also spend a relatively longer period of time in the nest before fledging. When in the woods, keep an eye out for snags (standing dead trees) and stumps, for they provide housing for many cavity-nesting birds. (Photo: Black-capped Chickadee removing wood chips from the cavity it’s excavating in a rotting stump.)
Most owls have feathered legs, but the feet and toes of some owls, especially those living in colder, higher latitudes, are also densely feathered. The feathers keep the feet of these birds warm, allowing them to hunt where snow is on the ground and temperatures are very low. Great Gray Owls (pictured), Snowy Owls and Northern Hawk Owls are all examples of this phenomenon. Owls living in warmer climes, such as Barn Owls, have sparsely feathered feet and toes, and tropical owls have nearly featherless feet. This variation can also be found within a given species that has a range that extends over many degrees of latitude, such as the Barred Owl.
I’m delighted to announce that my latest children’s book, Otis the Owl, has just been released. This book is a celebration of the serendipity of having had the opportunity to observe and photograph Barred Owl nestlings around the time of my grandson Otis’s birth. Otis the Owl is available from independent bookstores, online and from the publisher (click on cover image on my blog). It might make the perfect Valentine for your favorite 4 to 8 year-old!
Watch in wonder as Otis transforms from a tiny ball of fluff into a predator on the cusp of stretching his feathers beyond the safety of his family tree, in Otis the Owl, a real-life glimpse into the world of the woodland Barred Owl. Nature photographer Mary Holland’s breathtaking images capture the fierce beauty found in birds of prey, and candid commentary educates and enlightens while engaging audiences with questions, quizzes, and creative thinking. (Foreword book review)
There has been an unusually high number of Barred Owl sightings reported in northern New England and New York this winter, primarily from the road and near bird feeders. This phenomenon, particularly with owls, is usually attributed to either a current lack of food or an abundance of food during the most recent breeding season resulting in a dramatic increase in the owl population.
In the case of Barred Owls, it is the former. Unlike Snowy Owls, which vary the size of their clutch depending on food availability, Barred Owls typically have two young, regardless of the size of the rodent population. Thus, a plethora of progeny can be eliminated as a viable explanation for the abundance of Barred Owl sightings this winter, which leaves a scarcity of food as the primary reason.
For several weeks there has been a thick crust on top of the snow, which makes hunting for mice and voles difficult for raptors. Because they are very territorial, Barred Owls rarely wander outside of their territory, even when food is scarce. Thus, especially in the past few weeks, they have been desperate to find small rodents. Roads are one reliable spot where mice, voles and shrews are exposed, and bird feeders are most definitely rodent magnets. Hopefully weather conditions will allow birds of prey access to the subnivean layer (space next to the ground where small rodents travel, shelter and breed) before too many more Barred Owls starve to death. (Source: Joan Collins, NYS Ornithological Association, UV-BIRDERS List) (Photo: Barred Owl with recent Northern Red-backed Vole catch.)
Lying at the base of a large Eastern Hemlock I recently found two piles of bleached bones. One pile consisted of mostly vertebrae; the other pile had numerous tibias, humeri and ribs. All were the appropriate size and shape to have come from several Eastern Chipmunk skeletons – at least four or five. How did they end up in two distinct piles?
The lack of any fur indicated that regardless of how these bones came to be here, they were deposited quite a while ago. The lack of any partial skulls or jaw bones and the large number of bones in each pile led me to believe that these were not the remains of two pellets that had been regurgitated by resident Barred Owls. No wild owl pellet I’ve ever dissected, including the large pellets cast by Snowy and Great Gray Owls, has contained even half this many bones, and most contained at least part of a jaw bone.
If not pellets, then scat? How likely is it that a predator could catch and consume multiple chipmunks rapidly enough so that they would end up in the same pile of scat? One feasible explanation could be that a fox, coyote or fisher preyed on young, inexperienced chipmunks, but the bones were adult-size bones.
Perhaps these two piles are the remains of a predator’s cache – perhaps a bobcat?
The possibilities are endless as to how this chipmunk graveyard came to be. However, none of the theories proposed here can explain the dissimilarity between the types of bones in each pile. If any naturally curious readers have insight into this phenomenon, your thoughts are welcome!
An owl’s range of audible sounds is not unlike that of humans, but an owl’s hearing is much more acute at certain frequencies, enabling it to hear even the slightest movement of their prey under two feet of snow. When a noise is heard, the owl is able to tell its direction because of the minute time difference in which the sound is perceived in the left and right ear. If the sound is to the left of the owl, the left ear hears it before the right ear. The owl turns its head so the sound arrives at both ears simultaneously, at which point it knows its prey is right in front of it. Owls can detect a left/right time difference of about 0.00003 seconds.
Once an owl has determined the direction of its next victim, it flies towards it, keeping its head in line with the direction of the last sound the prey made. If the prey moves, the owl makes corrections mid-flight. When about two feet from the prey, the owl brings its feet forward and spread its talons, and just before striking, thrusts its legs out in front of its face and often close its eyes before the kill. (Photo: barred owl wings and feet imprints; inset: barred owl ear opening.)
The fledging of flightless Barred Owl chicks takes place four or five weeks after they hatch. Typically they perch on the rim of the nest cavity before climbing to a nearby branch. If there are no branches close by, the chicks will drop to the ground and climb a nearby leaning tree, where they perch and are fed by their parents. Juvenile Barred Owls begin short flights at approximately 10 weeks of age, attaining longer flights by 12 weeks. They are now learning to hunt, but continue to be fed by their parents until late summer or early fall. (Thanks to Alfred Balch for photo op.)
Young Barred Owls are fed by their parents from the day they hatch until late summer/early fall. During their first two weeks, food is delivered by the adult male to the adult female, in a bill-to-bill exchange. The female tears up the prey into swallowable bits and feeds them to her offspring. During this time the female does little hunting, but she begins to capture prey after about two weeks of brooding the young. At about this time, the young begin consuming whole prey on their own (see photo). Female prey deliveries are greatest immediately following sunset and immediately prior to sunrise, while male prey deliveries remain fairly constant throughout the night. (Photo: Barred Owl delivering Red-backed Vole to nestling.) (Thanks to Alfred Balch for photo op.)
Barred Owl eggs (usually two or three) are often laid in a tree cavity, where the adult female incubates them for roughly a month. Fuzzy, white, downy chicks hatch and remain inside the tree for four or five weeks while being fed by both parents. When the young owls are two or three weeks old, their white down is replaced with gray-buff secondary down, and they gain the strength to climb up the inside of the tree and peer out at the outside world. In and out they go, perching on the rim of the nest hole for half an hour or so as they await the arrival of their next meal, and then retreating back to the safety and warmth of their nest. (Thanks to Alfred Balch, naturalist extraordinaire, for photo op.)
If you live where the snow is actually melting, a labyrinth of vole tunnels may be revealing itself to you. These tunnels were excavated in the snow next to the ground in what is referred to as the subnivean layer. They lead from sleeping areas to known sources of food, and are advantageous to both mice and voles that travel in them – they provide thermal insulation by protecting them from the wind and cold, and they keep these rodents hidden from predators. Carbon dioxide, which builds up in the subnivean layer from animal respiration as well as CO₂ released from the ground, escapes through ventilation shafts, or air vents, that lead up to the surface of the snow.
Voles stay in these tunnels as long as the snow is deep enough not to expose them, finding food in the form of plants, seeds and bark from bushes and shrubs as they dig through the snow. This winter has provided voles, mice and shrews with an extended period of protection, as hungry barred owls attest to.
Barred owls are nothing if not resourceful when it comes to methods for finding food. Typically they sit on a high branch and scan the area for prey before dropping down to capture small mammals such as mice, squirrels as well as reptiles and amphibians. During summer months, they have been seen perched over water and swooping down to capture fish, as well as wading in shallow water to hunt for crayfish and fish. Barred owls have even been seen running along the ground and pouncing on amphibians.
Even with a myriad of hunting techniques, however, barred owls have had a hard time this winter, due to the depth of the snow (harder to hear and reach prey) and the time it is taking for it to melt. Small mammals, which compose the bulk of their diet, remain well hidden. Reports of barred owls perched patiently waiting and watching on or near bird feeders for unsuspecting rodents to expose themselves have become commonplace. Mice and voles that come out from under the snow to feed on spilled seed during the night are a life-saving source of food for these stressed birds. Warmer weather will hopefully soon improve hunting conditions for barred owls. Their gain will be our loss, for once again, as it should be, a sighting will become a far more rare occurrence. (Thanks to Emily and Joe Silver for photo op.)
Let me first say that the scenario I describe is conjecture, albeit conjecture based on the evidence posted yesterday. Today’s post may well tell you more about my train of thought when interpreting signs in the snow than the actual events that took place! The tracks were discovered and photographed by Sally Grassi of Camden, Maine, who saw a large bird (I thought that telling you this would be giving away too much!) devouring something while perched on the snow at night. The tracks that may appear to some as leading to and from the kill site are marks made by something that came out of the sky – they come from and lead to nowhere. I apologize if they were misleading. Given the myriad of ways this scene could be interpreted, the guesses made were strikingly on the mark. Kudos to Kathie Fiveash, who correctly guessed the prey species.
Plot: A bird of prey attacked another bird and proceeded to consume most of it.
Characters: As to the species of predator, the fact that this activity took place at night points to an owl, and the size of the bird eaten (deduced from the size of its remaining foot and bones) narrows the attacking bird down to most likely being a Barred Owl or a Great Horned Owl, both of which are found along the coast of Maine in the winter. (Snowy Owls are diurnal and therefore, even though there are individuals that have irrupted into New England this winter, the likelihood of it being a Snowy Owl is minimal.) Although we can’t know for sure which species of owl it was, chances are great that it was a Great Horned Owl, as they routinely eat large prey, and Barred Owls only occasionally feed on birds this size.
As to the identity of the prey — the geographic location, the time of year, the few remaining feathers and the color of the remnant (unwebbed) foot and leg appear to eliminate all but the Black Guillemot. Although totally black with white wing patches during the breeding season, this alcid (member of the family of birds that includes puffins, murres and auks) has a mostly grey/white plumage in the winter, and brilliant orange-red legs and feet year round. It can be found throughout the year along the coast of New England where it hunts for fish, crustaceans and invertebrates in shallow water near shore. (Thanks to Sally Grassi for Mystery Photos, to George Clark for confirming prey I.D. and J.J.Audubon for the Black Guillemot illustration.)
Barred Owls call year-round but their vocalizations increase and expand in February when courtship begins. No longer are their calls limited to their year-round “who-cooks-for-you — who-cooks-for-you-all.” Males and females engage in “duets,” as well as many other vocalizations, including cackles, hoots, caws and gurgles. Those who sleep with open windows may feel like they are in the middle of a jungle inhabited by hundreds of raucous monkeys.
Barred Owl courtship is not strictly vocal. Male Barred Owls display by swaying back and forth and raising their wings, while sidling along a branch in close proximity to a female. Courtship feeding and mutual preening also occur prior to copulation. The nights of February are filled with amorous avian calls and gestures.