An online resource based on the award-winning nature guide

Posts tagged “Strix varia

A Feathered Visitor

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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com  and click on the yellow “donate” button.


Hungry Barred Owls Near Feeders

3-4-19 barred owl _U1A2992Over 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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


An Owl’s Digestion Process

11-26-18 -barred owl coughing up pellet2 _U1A1839Most 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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to https://naturallycuriouswithmaryholland.wordpress.com  and click on the yellow “donate” button


Barred Owls Fledging (But Not Flying Yet)

5-21-18 barred owl fledglings3 _U1A3239

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!)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Snow Stories Begin

1-5-18 owl print in snow - Rob Foote IMG_4571 (002)

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.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Barred Owl Parents Providing Fledglings With Food

6-2-17 barred owls 327

Young Barred Owls are fed from the time they hatch (four to six weeks old) until late summer or early fall, months after they have fledged and long after they are capable of flight. When first out of the nest, the fledglings cannot fly, and thus are totally dependent upon their parents’ continued delivery of prey. The fledged young initially stay near one another and the nest site. The parents continue to feed them, and as the young become more mobile they slowly move away from the nest tree. Flight is attempted between the ages of 12 and 15 weeks. The first attempts are, as you would imagine, rather awkward, but as their wings strengthen, the young owls’ flying skills improve. Even so, the parents continue to feed them through the summer and often into the fall, when prey deliveries slow down and eventually cease, forcing the young to disperse. (Photo: Recently-fledged Barred Owl chick eyeing the Flying Squirrel its parent is delivering.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.

 


Barred Owl Chicks Fledging

5-25-17 barred owl fledging2Unlike 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)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Barred Owls Parents Tending Chicks

5-12-17 adult owl in nest hole 241For 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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Feathered Fishermen

4-24-17 barred owl IMG_8141

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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


The Feathered Feet of Northern Owls

3-14-17 great gray owl2 164

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.

Naturally Curious is supported by donations.  If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.

 

 


Snow Conditions Making Life Challenging For Barred Owls

1-20-17-barred-owl-and-red-backed-vole-l-040

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.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.

 


Barred Owl Chicks Fledging

6-18-15  barred owl fledged 155The 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.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Barred Owl Chicks View The World For The First Time

6-4-15  barred owl chicks2  100 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.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Patient (and Hungry) Barred Owls Visit Feeders

3-12-15 barred owl 152Barred 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.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Barred Owls Courting

2-11 barred owl 057Barred 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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Contents of One Barred Owl’s Stomach

11-7-14 vole, shrews and mouse 027Fantastic guesses, given you had no measurements to work with. Very creative, indeed. Yesterday’s mystery photo was a packed version of the bodies displayed today.

Owls swallow small prey, such as mice and voles, whole, while larger prey is torn into smaller pieces before being swallowed. Once eaten, prey goes directly into the owl’s stomach, as owls have no crop, and thus no ability to store food for later consumption.

Like other birds, owls have a stomach with two chambers — one is the glandular stomach, or proventriculus, (yesterday’s mystery photo) which produces enzymes, acids and mucus and begins the process of digestion. (Because the acids are weak, only the soft tissues are digested.) The second stomach is the muscular stomach, or gizzard, also called the ventriculus. The gizzard lacks digestive glands – it serves as a filter, holding back bones, fur, teeth and feathers that are difficult to digest. The soft parts of the food are ground by the gizzard’s muscular contractions, and allowed to pass through to the rest of the digestive system.

Several hours after an owl has eaten, the indigestible parts remaining in the gizzard are compressed into a pellet the same shape as the gizzard. The pellet travels back to the proventriculs and remains there for up to ten hours before being regurgitated. Because the stored pellet partially blocks the owl’s digestive system, new prey cannot be swallowed until the pellet is ejected. If more than one prey is eaten within several hours, the remains are consolidated into one pellet. (In this case, one very large pellet!)

Update: I left the contents of the deceased Barred Owl’s proventriculus outside last night, and a resident Barred Owl recycled the Meadow Vole and Masked Shrew.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Juvenile Barred Owls Mastering Flight

barred owl-fractured wing 062Typically Barred Owls in northern New England hatch in May and fledge, or leave their nest, in June at approximately four to five weeks of age. Unlike most young birds, Barred Owl nestlings leave their nest before they can fly. They initially perch on the rim of the nest and then climb to a branch on the nest tree, eventually dropping to the ground and climbing a nearby leaning tree to perch. The parents feed their young from the time they hatch until late summer or early fall. The fledglings begin short flights at approximately 10 weeks of age, attaining longer flights by 12 weeks. The pictured Barred Owl may have been mastering flight when it fractured a wing and ended up on the ground, soaking wet and very vulnerable to predation. (Thanks to Bob Moyer for photo op and Vermont Institute of Natural Science’s Wildlife Rehab staff for setting wing.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Barred Owls Frequenting Feeders

4-4-14  barred owl with suet IMG_5432The number of Barred Owls seen near bird feeders recently makes one question whether these birds are, in fact, in dire need of food. Certainly the extended period of deep snow this winter has made finding prey challenging. Fortunately, the local bird rehab center (Vermont Institute of Natural Science) has not been inundated with starving owls, which indicates that other factors may be involved in the increased number of sightings near homes and feeders. One of these factors could be that Barred Owls are currently laying and incubating eggs, and a few early nesters may even be providing food for young owlets. Whatever the reason, the accessibility of rodents that are attracted to feeders and the food itself that’s in the feeders allows us an all-too-rare glimpse of this common owl. (The mystery of repeatedly finding my suet feeder on the ground every morning was finally solved when I took this photograph – look closely at what the Barred Owl is clutching in its talons.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Owl Ears

3-26-13 barred owl ear IMG_7161It’s well known that owls have an acute sense of hearing — some species, such as the barn owl, hunt nocturnally by sound alone. An owl’s asymmetrically-placed ears are located beneath the feathers at the edge of its facial discs. This placement, along with the shape of the external ear canals, is thought to contribute to an owl’s keen ability to locate sound. The flesh-colored fold of skin that you see in front of this barred owl’s ear is movable, and reflects and concentrates sound waves coming from behind the bird.


Barred Owl Pellet

This slideshow requires JavaScript.

Having posted a barred owl regurgitating a pellet, it only seemed fitting to post the pellet itself.  Many birds, not just birds of prey, form pellets that consist of the indigestible parts of prey they’ve eaten – fur, feathers, claws, teeth, fish scales, exoskeletons of insects and crustaceans and parts of plants.  In general, the larger the bird, the larger the pellet – the pellets of most birds of prey are an inch or two, and they’re roughly half an inch for a small songbird.  With birds of prey, likely spots to find pellets are beneath roosting and nesting sites.  In addition to getting rid of indigestible matter, the casting of pellets is thought to improve the health of a bird by scouring its throat, or gullet.  It takes anywhere from 6 to 16 hours after a hawk or owl has eaten for it to cast a pellet, and it may be necessary for the bird to do so before it eats its next meal.  Dissecting pellets is an effective way of determining a bird’s diet.  The pellet of a golden eagle in Oregon contained a leg band that had been placed on an American wigeon (a species of duck) about four months previously, a thousand miles away! (Pictured are a 1 1/2-inch barred owl pellet and the contents, minus the fur, of several pellets.)


Barred Owl Coughing Up Pellet

Roughly six to ten hours after consuming prey, owls, hawks and many other birds cough up a small pellet that consists of the indigestible bones, fur, etc. of the prey it’s eaten. The barred owl in this photograph was in the process of coughing up such a pellet. While pellets are hard to come by (they are well camouflaged on the forest floor), owls caught in the act of producing them are even more rare!


Barred Owl Diet

This is pure conjecture, but here goes. Barred Owls are known to consume small mammals, birds, reptiles, amphibians, fish and invertebrates. I have repeatedly encountered a Barred Owl lately near a pool of water in a brook that has all but dried up. Fish have become trapped in this pool due to the dryness of the summer, and are easy pickings for predators. Even though studies have shown that fish are a very small percentage of a Barred Owl’s diet (2.5% in owls from New Jersey, New York and Connecticut during the breeding season), I am betting that the owl that I flushed yesterday that was perched right next to the isolated pool in the brook was spending the day (and night?) at his favorite fishing hole. Three times it took off from its perch as I approached, but only flew a few feet away each time. Perhaps fish or frogs kept it from disappearing further into the woods.


Barred Owl Pellet and Droppings

There are two subjects in this photograph – one is dark and round (left) and the other is whitish-yellow and brown, and string-like (right).  One came out of a barred owl’s mouth; the other came out the opposite end.  Do you know which is which?  The round, brown object is an owl pellet which owls (and many other birds) cough up roughly 6 – 10 hours after consuming a meal.  It is just about odorless, and consists of the indigestible parts of the owl’s prey — bones, teeth and nails wrapped in the fur of, in this case, a vole. (The fur keeps sharp bones from tearing the owl’s esophagus when the pellet is coughed up.)  Different owl species have different sized pellets, and typically the larger the owl, the larger the pellet. (The average barred owl pellet is 2 ½” long and 1” wide.)   A great gray owl pellet (3”-4” long and 1 ½” wide) I found contained the skulls of three small rodents, in addition to other bones.  The whitish substance is the owl’s semi-solid waste. It consists of white uric acid and feces which are excreted through the bird’s cloaca, an opening that is used not only for waste disposal, but also for mating and egg laying.