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Owls

Snowy Owls Headed North

4-21-14 flying snowy 046The record number of Snowy Owls that spent the winter in New England are turning up in all sorts of new locations now that they are on their way back to their breeding grounds on the open tundra and stopping to refuel along the way. Although many were young birds, and won’t breed this year, the adult owls will when they reach the Arctic in a few weeks. First, the males perform aerial and ground displays. After mating, the female selects a nest site. In addition to having a sufficient food supply, the site must be snow-free, not subject to flooding, and command a view of its surroundings. The latter is achieved by making their nest on a hummock, or slightly raised surface of bare ground. The female scrapes a shallow depression in the earth with her claws, twirling around to make a form-fitted hollow. No insulating material is added to this depression – no vegetation, no feather lining. Eggs and nestlings are totally dependent upon the mother’s warmth, transmitted via the large, featherless, pink patch of skin on her belly known as an “incubation patch.” The female alone incubates the eggs and broods the young chicks while the male provides food for his entire family.

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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.)

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Snowy Owl Pellet

3-25-14 snowy owl  203Your knowledgeable ID skills regarding yesterday’s Mystery Photo were most impressive!

Snowy Owls are the heaviest owls in North America, weighing roughly 4 pounds (a Great Gray Owl is only 2.4 pounds). A lot of fuel is needed to power this magnificent raptor. In the Arctic, where they live, lemmings are their preferred prey — one owl may eat more than 1,600 of these small rodents in a single year. This winter the Northeast has experienced record numbers of visiting Snowy Owls. A banner year for the Arctic lemming population followed by prolific nesting success for Snowy Owls resulted in an unprecedented “irruption” of these owls further south this winter.

While we do have lemmings in New England, they are uncommon, so Snowy Owls have relied on our small rodent, squirrel, rabbit and hare populations for food. Those owls wintering on the coast, where dunes and moors closely resemble their tundra habitat, have also taken advantage of the large number of sea ducks. As witnessed and described by Nantucket ornithologist Edie Ray, the owls fly up to great heights over the sea, spot waterfowl and then plummet down to just above the surface of the ocean where they sink their talons into a “sitting duck.” As a result, the indigestible bones, teeth and nails of prey are protectively wrapped in feathers as well as fur in the large pellets coughed up by these owls. (Snowy Owl locators: Edie Ray and Sadie Richards; Snowy Owl pellet finder: Sadie Richards)

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Avian Toe Arrangment

3-17-14 mourning dove tracks 004As opposed to humans, who use the entire bottom of their feet for support, birds stand and walk only on the ball of their foot and with their toes. When you look at a bird’s leg, what appears to be its knee, bending backward instead of forward as it does in humans, is actually its heel.

Most birds have four toes, arranged differently according to the life style of the bird. Songbirds, as well as most other birds, have three toes pointing forward and one pointing back. Most woodpeckers, being active climbers, have two toes pointing in each direction, which provides added clinging support. The outer toe (of the three forward toes) of ospreys and owls is reversible, so that they can have two toes in back should they need to get a better grasp on slippery fish or other prey. Some birds that do a lot of running, such as sanderlings and most plovers, have only the three forward toes. (Photo: Mourning Dove tracks)

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Snowy Owl Invasion

2-4-14 lemmings-at-nest4In a typical winter, sightings of snowy owls are a regular occurrence in the Northeast, but this winter, as most New Englanders are aware of, we’re experiencing a banner irruption year, with individuals appearing in greater numbers from the north than they have in decades. In the past, hunger and lack of prey in the Arctic have been the accepted explanation for this influx of northern predators, but this year that theory has been put to a test, as 2013-14 visitors are arriving in excellent condition. Last summer the lemming population (snowy owls’ food of choice, with one owl eating up to 1,600 lemmings in a year), as well as other prey species, exploded in northern Quebec. It’s thought that snowy owls amass to nest in areas where prey is abundant, and it appears that this is exactly what happened in Quebec. The rodent explosion resulted in exceptionally large broods (up to 12 chicks per pair of owls). In part due to competition with older owls, this large first-year population of owls moved south this winter, and we are the beneficiaries. To see the movement of this year’s irruption, go to http://www.projectsnowstorm.org, where this photograph of a 70 lemmings/8 voles-lined snowy owl nest by Christine Blais-Soucy originally appeared.

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Northern Hawk Owl

n. hawk owl3- 231The Northern Hawk Owl is a bird of the remote Alaskan and Canadian boreal forests. Its name reflects the fact that this diurnal owl has both the appearance and behavior of a hawk, specifically, an accipiter. Although the Northern Hawk Owl winters throughout its breeding range, it periodically erupts southward into southern Canada and the northern United States. Sightings of this bird are rare in Vermont, but in recent winters, including the current one, there have been some. As with Snowy Owls, the magnitude and extent of these winter irruptions are thought to correlate with high reproductive success followed by severe winter conditions and decreased prey availability, but much remains to be understood about their winter dispersal habits. What we do know is that the Northern Hawk Owl’s skills as a hunter are very impressive. It can detect prey (small rodents, grouse, hares) by sight at a distance of half a mile and just using its ears can find prey under a foot of snow.

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Interpreting a Kill Site

12-18-13 hawk kill IMG_4136When there’s snow on the ground and you come upon a site where a predator successfully caught prey, there are usually signs that will help you determine who the main players were. In the above scene, remnants of red squirrel fur confirm the identity of the prey. If you look at the top of the image, you can make out a faint wing impression. Although not in this case, both wings of an avian predator often touch the surface of the snow, allowing you to measure the wingspread, and this information can help to eliminate some species of raptors. Birds of prey often defecate at a kill site. In the lower left corner of the photograph, as well as to the left and right of the packed area where the squirrel was eaten, you can see white (uric acid) bird droppings. Given that it is a hawk or an owl, knowledge about their respective evacuation habits will allow you to narrow down the possibilities even further. Owls tend to let their droppings do just that – drop, leaving small plops on the ground. Hawks, on the other hand, tend to forcefully eject their droppings some distance away. The long, thin streaks at this site were definitely propelled outwards, making it likely that the predator was a hawk. Familiarity with the hawks that overwinter in your area can help pinpoint which species it could be.

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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.


A Great Christmas Present!

If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”

In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e  book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”

I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!


Barred Owl Pellet

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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!


Great Horned Owl Fledglings

Hardy birds that they are, Great Horned Owls are one of the earliest nesting birds — you can find them on nests in January, February and March, even in northern New England. Eggs are incubated for about a month, typically in March or April with young usually hatching in May or June. The nestlings remain in the nest for six or seven weeks before fledging. Unable to fly until they’re ten or twelve weeks old, the fledglings follow their parents around and continue to be fed and cared for by them until the fall. These two fledglings were sticking close together as they made their raspy begging calls from high in a white pine. Both their calls and the down that was visible on their heads told me that they were this year’s young.


Striped Skunk

Although you would think that no predator would think of preying on, much less eating, a striped skunk, there are a few mammals, including coyotes, foxes and bobcats, that do just that, but only if they are in danger of starving.  One predator that routinely dines on skunks is the great horned owl.  One summer night I made out the silhouette of an owl flying in my direction, and as it flew by me its identity was confirmed by the skunk-like odor that accompanied it. 

 


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.


Northern Saw-whet Owl

Saw-whet Owl

One night this week I became aware of a series of whistled “toots,” all the same pitch, coming from the adjacent woods. This far-reaching, distinctive call comes from a surprisingly small owl, the Northern Saw-whet — one of our most common owls, whose common name comes from the “skiew” call that is made when it is alarmed. This sound has a resemblance to the whetting of a saw. Although a Saw-whet only weighs about as much as a robin, you would never know it from the volume and carrying power (over 300 yards) of its call. Typically the male calls only during the mating season, in an attempt to attract a female with whom it will mate. The female then selects the nesting cavity, typically a Northern Flicker or Pileated Woodpecker hole, usually in March or April. This pint-sized raptor (weighing less than 3 ounces, and measuring 8 inches in length) feeds mainly on deer mice. Unlike most owls, it does not swallow the mouse whole, but rather tears it in half, leaving the second half for another meal.


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