An online resource based on the award-winning nature guide – maryholland505@gmail.com

January

North American River Otters Use Abandoned Beaver Lodges As Dens

North American River Otters use dens (called holts) for giving birth and for shelter from weather extremes.  Den sites are usually close to the water line of rivers and lakes, and have multiple entrances underwater as well as on dry land.  They are often excavated under trees or rocks or in river banks, but otters also use abandoned muskrat burrows and beaver lodges as shelters (cohabitation with beavers has also been documented – see https://naturallycuriouswithmaryholland.wordpress.com/2013/02/22/beaver-otter-cohabitation/).

One of the most obvious and distinctive signs of otter occupancy of a den is the presence of their scat in the vicinity.  It usually has little form; rather, it consists of loose piles primarily composed of fish scales. Pictured is an abandoned beaver lodge that is currently occupied by several otters whose scat in the foreground and tracks and slides in the vicinity confirm their presence. A lack of any beaver sign indicates the lodge has been abandoned by its original inhabitants.

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Downy Woodpeckers Foraging For Overwintering Insects

Three-quarters of a Downy Woodpecker’s diet consists of animal matter, mostly beetles, weevils, ants, wasps, bees, true bugs, caterpillars, spiders and snails.  The pictured male Downy has located and is consuming some overwintering wood boring beetles.  

 Notice he is on a small branch.  Research shows that male Downys tend to forage on small-diameter branches and stems of weeds, whereas females are often found on larger branches and the trunks of tree.  

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Blue Eastern Cottontail Urine

A recent (1/22/21) Naturally Curious post on the color of Eastern and New England Cottontail and Snowshoe Hare urine mentioned that occasionally it turns blue after a few minutes in the sun due to consumption of the twigs and bark of the invasive shrub, European Buckthorn (Rhamnus cathartica). At the time of the post I had not had the opportunity to photograph it, but recently came across some so thought I would share it with you today!

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Eastern Gray And American Red Squirrel Food Caching Strategies

Red and Gray Squirrels both store food for the winter, but their food caching strategies are very different. Gray Squirrels store many hickory, oak and beech nuts by engaging in “scatterhoarding” – burying one nut at a time, each in a different spot.  Most popular are acorns, which fall into two groups — those grown by white oak species , and those from the group of red oaks. The acorns of red oaks have delayed germination, making them ideal for storage through the winter.  Those of white oaks germinate sooner, in the fall, so are more readily eaten than buried.  (If a Gray Squirrel chooses to bury an acorn from one of the white oaks, it often removes the embryo before doing so, which kills the seed and prevents germination.)  

Red Squirrels, on the other hand, practice “larderhoarding” –  collecting green cones in the fall (up to 15,000 or more) and storing them in one place (generally in the middle of their territory) where they are fiercely protected. A large pile (midden) can result, under which new cones are placed. This cool, moist environment keeps the cones sealed, protecting the seeds from being eaten by mammals and insects that are unable to open the cones.  Middens can contain enough food to last one to two seasons. (Photo: Exceptionally large Red Squirrel midden submitted by Steve Bird of the Coastal Mountains Land Trust, Belfast, Maine)

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Colorful Cottontail & Hare Urine

With snow on the ground, it becomes evident that the urine of Eastern Cottontails, New England Cottontails and Snowshoe Hares is occasionally colored red or blue!  This is not indicative of disease — it is a result of their diet. 

Phytochemicals are responsible for this oddity. Plants contain compounds that contribute to the plants’ color, taste and smell. When the plants are eaten by a rabbit or hare, these compounds pass through the animal’s system and come out in its urine, affecting the urine’s color. I am not aware of which plants produce the more commonly seen red urine, but compounds in the twigs and bark (the fruit is not often eaten by hares and rabbits) of the invasive European Buckthorn (Rhamnus cathartica) can turn rabbit and hare urine blue. (Initially the urine is yellow, but after about ten minutes’ exposure to the sun, it turns blue.) 

As winter progresses, your chances of seeing blue urine increase, as much of the easily accessible nutritious food has been harvested and rabbits and hares resort to eating the less desirable twigs and bark of European Buckthorn. (Photo: Snowshoe Hare tracks and urine)

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Birds Gathering Grit On Dirt Roads & Roadsides

Birds compensate for their lack of teeth with a two-parted stomach, the first of which (proventriculus) secretes digestive enzymes and the second of which (a muscular gizzard) grinds the food they’ve eaten into small digestible bits.  Birds that eat hard seeds and nuts tend to have thick, muscular gizzards, while those species that eat very easily-digested foods such as soft-bodied insects, soft fruits, or nectar often have very small and thin-walled gizzards.  Many birds whose diet consists of hard substances, including seed-eaters, swallow grit (often why you see them on dirt roads or the sides of plowed roads where dirt has been exposed) to enhance the gizzard’s ability to pulverize food.

At this time of year, American Goldfinches, Common Redpolls, Snow Buntings, Tree Sparrows and Eastern Bluebirds (among others) can be found swallowing roadside grit to help grind up the seeds that they consume.  (Photo:  While a majority of their summer diet is insects, Eastern Bluebirds consume many fruits (containing hard seeds) during the winter, a change in diet that allows them to remain in northern New England throughout the year.)

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Muskrats Foraging

Usually at this time of year, Muskrats are restricted to foraging beneath the ice and eating their mostly herbivorous diet inside “push-ups” — huts made out of excavated vegetation that have been hollowed out and serve as protective outposts where they can eat and rest. Because of warmer weather this winter, many ponds have retained open areas where Muskrats (and Beavers) can climb out of the water and enjoy sunshine (if they’re lucky) and fresh air while they eat.

Unlike Beavers, which store their winter food in a pile adjacent to their lodges in the fall, Muskrats forage for food on a daily basis throughout the winter. While occasionally they eat small fish, clams, snails and turtles, Muskrats’ preferred diet is the roots, stems, leaves, and fruits of many water plants, such as cattail, water lilies, and rushes. Equipped with a thick, waterproof coat of hair, they are capable of remaining submerged up to 15 minutes collecting food due to a decreased heart rate and oxygen stored in their muscles.

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Snow Buntings Feeding

Congratulations to Kathie Fiveash, the first NC reader to correctly identify the tracks and feeding sign in the latest Mystery Photo as those of Snow Buntings (Plectrophenax nivalis).  These birds began arriving in the northern half of the United States from their summer home on the northern tundra last fall and will remain here until March, when they begin migrating back to their breeding grounds.

In the winter, 97% of a Snow Bunting’s diet is weed seeds, including those of knotweed, ragweed, amaranth, aster, goldenrod, grasses and grains. These birds forage on the ground, collecting seeds from the protruding stems of tall weeds, occasionally reaching or leaping up to take seeds from taller stems, jumping against stems to scatter seeds or bending stems over by stepping on them. (Birds of the World, Cornell Laboratory of Ornithology)

While foraging, Snow Bunting flocks are constantly restless, frequently flushing rapidly and low over the ground for short distances.  A flurry of birds, much like snowflakes, fills the air nearest the ground for a few seconds while they relocate to a new area. Birds at the back of the flock fly forward to the front, creating the impression that the flock is rolling along.

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Mystery Photo

If you think you know who has been feeding here, go to the Naturally Curious blog (www.naturallycuriouswithmaryholland.wordpress.com) and enter your answer under “Comments.” (Hint: photo taken in large agricultural field in Champlain Valley of Vermont.) Answer will be revealed on Monday, January 11. (Difficulty 1-10 = 10)

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What Determines The Internal Air Temperature Of An Active Beaver Lodge In Winter?

Regardless of the outside temperature, the interior of occupied beaver lodges has a fairly stable temperature of about 32°F.  This is due to several factors, one of which is insulation. Beavers spend much of the fall collecting and stuffing mud into the cracks between the branches that provide a framework for their lodge (leaving a mud-free air vent at the top of the lodge).  This mud as well as any snowfall that occurs during the winter help keep out the cold and retain the warmth that the resident beavers’ bodies radiate. 

A comparison of the (cooler) interior temperature of bank dens and that of open-water lodges confirms that the temperature of the substrate underlying a lodge also contributes to the air temperature of the chamber.

Lastly, heat produced by beavers raises the temperature of a lodge above that derived from the lodge substrate.

(Photo: beaver lodge on a morning cold enough to show “beaver breath” escaping through the air vent that runs up through the center of the lodge to its peak. Thanks to Kay Shumway for photo op.)

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Wild Turkeys Foraging on Sensitive Fern Fertile Spores

Congratulations to Deb Marnich, the first of many Naturally Curious readers who identified the Sensitive Fern fertile frond visitors as Wild Turkeys.  I had neglected to check and make sure I hadn’t addressed this subject recently on this blog, which is my custom with every post, and indeed, just a year ago there was a post on this very subject.  Judging from the number of correct entries, either I have a very informed readership or their memory is better than mine – quite possibly both!

Wild Turkeys usually forage in flocks as they search the ground for food. Acorns, hickory nuts, beechnuts, ironwood and white ash seeds, hawthorn and witch hazel fruits make up a lot of their diet in fall, winter and spring. In the summer, seeds of grasses and sedges as well as invertebrates are eaten. In winter, when snow has accumulated, leaves of sedges, evergreen ferns, hemlock buds, burdock seeds and spore-covered fronds of sensitive ferns tend to be more accessible and readily eaten.

The fertile fronds of Sensitive Fern (Onoclea sensibilis) persist all winter, sticking up out of the snow as if beckoning to hungry turkeys. Upon finding a clump of these fertile fronds, a turkey will peck repeatedly at them, causing the sori (clusters of sporangia which produce and contain spores) to burst and release thousands of spores onto the surface of the snow.

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Mystery Photo

Any idea who has been visiting these Sensitive Fern fertile fronds?  If so, go to the Naturally Curious blog, scroll down to “Comments” and enter yours.  Answer will be revealed in Friday’s post.

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White-tailed Bucks Shedding Antlers

White-tailed Deer bucks grow and shed a pair of antlers annually.  The main purpose of these bony growths is to serve as weapons against rival bucks during rut, or mating season.  During this time in the fall, prior to their 24-hour receptive period, does release chemicals to signal their readiness to bucks.  These chemicals keep the bucks’ testosterone level high, which in turn keeps antlers firmly attached to their heads.  Once rut is over, does stop emitting these chemicals, and as a consequence, the bucks’ testosterone level drops significantly.

When a buck’s testosterone level drops, it triggers cells called osteoclasts to become more active in the buck’s pedicles, the permanent bony bases which anchor the antlers to the buck’s skull. As a result, calcium is extracted from the pedicles which weakens the antlers’ connection to the buck’s skull, and eventually the antlers drop off.

It is rare that both antlers drop at the same time – usually there are four to eight days between the loss of the first and the second antler. I assumed that bucks needed to knock their antlers against something hard, such as the trunk of a tree, in order to get them to fall off.  However, years ago I witnessed a buck shedding an antler simply by dropping his head and then quickly flicking it upwards, sending an antler flying through the air. (Note pedicle where antler used to be attached. Photo by Alfred Balch)

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Coyotes Scavenging

Coyote tracks from three different directions led to an area where a deer’s well-cleaned skull was the only remnant of a communal meal. It had been dug up from a spot nearby where it had been cached, and carried to a more protected area to work on.  Coyotes are omnivores, but about 90% of their diet consists of mammals.  Coyote scat I’ve examined has included, among other things, the hair of Muskrat, Snowshoe Hare, White-tailed Deer and small rodents as well as feathers, grass and apples.

Coyotes are commonly blamed whenever there is a decline in the White-tailed Deer population.  Studies involving the removal of deer populations in a given area have not found any evidence that Coyote removal caused an increase in the deer population, nor did it affect the overall deer population growth. The fact that Coyotes are not causing deer populations to decline can also be seen in the devastating effect White-tailed Deer are having on forest ecosystems throughout the eastern United States as the Coyote population increases.

That’s not to say Coyotes don’t hunt deer – they do, primarily in the spring (fawns) and in the winter, especially when there is enough snow and/or crust to slow deer down but not Coyotes. However, much of their venison consumption is a result of their scavenging deer carcasses, which they do any time of year. Examine Coyote scat and the chances are great you will find deer hair in it; chances are also great that it came from a carcass, not a living deer.

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North American River Otters Sliding & Gliding

North American River Otters spend much of their time foraging.  They often have a circuit they travel along rivers and lakes which takes them up to a week or more to complete.  In between bodies of water, they travel overland on well-used paths, often during the day in winter.

These circuits are miles long, and for much of the time otters lope along in typical weasel fashion.  However, in winter the snow permits them to occasionally flop down on their bellies, tuck their front feet next to their chest and push off with their hind feet as they slide effortlessly on top of the snow, both down slopes as well as along flat surfaces.  Once they obtain a certain speed, they give their hind legs a rest and lift them off the ground so as not to slow them down as they slide (see photo).  Otters have been clocked up to 17 miles per hour running and sliding in this manner.

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Beavers Foraging

Even in the coldest of winters, there is often a thaw around this time of year that frequently allows beavers to escape the cold (+/- 34°F) dark lodge where they reside during most of the winter.  Our most recent thaw was such that in many beaver ponds, ice didn’t even have to be broken in order for resident beavers to forage for food on land.

When beavers are confined to complete darkness (under the ice) their 24-hour circadian cycle extends to a 28 hour day. During this time beavers sleep for longer periods at a time and thus need less food.  As spring approaches and the days lengthen, the slightest exposure to daylight will reset the beaver’s biological clock back to the circadian cycle. (Leonard Lee Rue, Beavers)  (Photo by Alice Trageser)

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American Goldfinch Plumage Anomaly

Molting, the replacement of all or some of a bird’s feathers, occurs in response to a mixture of hormonal changes brought about by seasonal changes. This process serves to replace worn feathers (they cannot repair themselves) and can play a part in seasonal camouflage as well as attracting a mate.

All of our small songbirds have a complete molt, replacing all of their feathers in late summer. In addition, many species have a partial molt (replacing body feathers but not wing or tail feathers) in the spring.

According to David Sibley, American Goldfinches begin to molt all of their (alternate/breeding plumage) feathers in September, with the males replacing their brilliant gold feathers with much duller feathers by November.  Come spring and the breeding season, male goldfinches replace their dull (basic/non-breeding) body feathers (but not the wing or tail feathers) with new, bright feathers.

Imagine my surprise when I spied a brilliantly colored American Goldfinch at my feeder this week.  According to ornithologist George Clark, it’s usually March before one starts to see an American Goldfinch in breeding plumage. One can only wonder what prevented this individual from molting its breeding plumage in the fall. (Photo: male American Goldfinch, winter plumage; inset – male American Goldfinch in breeding plumage in January)

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Bobcats Foraging

Bobcats are active all winter, particularly at dawn and dusk, when their primary prey (hares and cottontails) are active.  Mice and voles are also a significant part of their diet, and occasionally larger-bodied male Bobcats successfully prey on White-tailed Deer.  The pictured tracks reveal that while foraging for food, a Bobcat discovered the remains of a Porcupine that had been killed and skinned by a Fisher.

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Wrong Mystery Solved!

My apologies to the 50+/- NC readers who responded with great creativity to the latest Mystery Photo!  The photographer and I had a miscommunication, and I misdirected readers about the actual mystery you were to solve!  I thought the photographer had observed a goose making the two parallel lines in the ice with their feet (nails) as they landed. However, these two lines are actually just cracks in the ice, as many readers guessed (Susan Cloutier was the first to correctly identify them).   While Canada Geese do use their feet as well as their wings as brakes to slow themselves down before they land and they do have a hind toe which conceivably could scratch the ice, the landing imprints of the geese (and what I should have asked readers to identify) are actually in the upper half of the photo (see red circle) where the snow has been plowed aside, revealing the darker ice underneath.   The presence of a considerable amount of goose droppings confirms the identity of the birds landing on the ice.

Observers often ask how Canada Geese or other waterfowl can stand for long periods of time on frozen lakes and ponds.The legs and feet of waterfowl play an important part in maintaining their body temperature.  In the summer, their large, flat feet cool their body by releasing a good deal of heat.  In winter, the heat exchange system (counter-current circulation) in a bird’s legs prevents a great deal of body heat loss due to the fact that the warm arterial blood going into the bird’s feet is cooled by the colder blood traveling back to the body in adjacent veins.  Constricted blood vessels in their legs further conserves heat. (Photo by Mike Hebb)

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Seeing The World Through A Naturalist’s Eyes

There are innumerable resources for anyone interested in identifying any part of the natural world — field guides to feathers, fungi, tracks, butterflies, mosses, bird nests — the list goes on and on.  What has been lacking, in my opinion, is an introduction to the art of discovering what it is that you may then wish to identify.

If you are very lucky in your lifetime, you may cross paths with someone who heightens your awareness of the natural world that surrounds you and teaches you how to look at it and ask the questions that will provide you with insight into it.  These are skills that one rarely finds in a book.  To the good fortune of all who open the pages of The Naturalist’s Notebook – An Observation Guide and 5-year Calendar Journal for Tracking Changes in the Natural World Around You, this book does this and more.  Not only does it present the reader with the keys to observing the natural world around them, it provides the means to record these observations so that the daily details one observes are preserved for posterity and for comparison in years to come.

I can’t think of a better way for a budding or experienced naturalist to start a new year than to open the pages of this book and delve into the words that will allow them to connect themselves more intimately to the world that is right outside their door. Not only would they reap the benefit of the morsels within this book, but all royalties from the sale of The Naturalist’s Notebook are donated to conservation and environmental education. Nathaniel T. Wheelwright and Bernd Heinrich have given the world a true gift – one that could ultimately affect the future of this fragile planet we live on.

NB:  In addition to this publication, Nathaniel Wheelwright has produced an exceptionally informative and entertaining series of short videos about the natural history of eastern North American plants and animals: https://research.bowdoin.edu/nature-moments/.

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Two For One

2-15-19 cardinals _U1A8442Thanks to warmer temperatures and a vast increase in the number of bird feeders, Northern Cardinals have expanded their range northward as far as Canada over the past century. Males get far more attention than females, due to their year-round brilliant red plumage. However, the female Cardinal is equally striking with her more subtle tan plumage highlighted with touches of red. Believe it or not, it is possible, albeit very rare, to find both of these plumages on one bird.

Recently an interesting phenomenon known as a bilateral gynandromorph was recorded in Pennsylvania — a cardinal whose body is half male, half female. (For a detailed explanation and video, go to https://www.nationalgeographic.com/animals/2019/01/half-male-half-female-cardinal-pennsylvania/?fbclid=IwAR2KbCmxuGxtGmKug2eLPS9JD6Vf_KV93OWgy0UsKuMAO-p_2soISJgM400.) Not just the plumage, but the anatomy of this bird is half male, half female. The way in which this gender division exists has a unique effect. According to National Geographic, “Most gynandromorph individuals are infertile, but this one may actually be fertile as the left side is female, and only the left ovary in birds in functional.”

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Otter Holes

1-30-19 otter hole img_5596A pond can have one to two feet of ice on top of it, yet North American River Otters somehow manage to find a way to come up through the ice. How do they do this? Careful observation reveals that the ice where otter holes are found is thinner than most of the pond’s ice. Otters rely on spring-fed open water and areas of thin ice for surfacing holes. Here they break through the ice and often drag larger fish out onto the ice to eat them.

If otters are feeding in a beaver pond and they can’t find openings in the ice for fishing, they have been known to tunnel into beaver dams for access to open water. In late winter, water levels sometime drop below the ice, leaving an air space that lets otters swim and hunt beneath the ice without the need for holes. (Look closely at opening to see the actual hole beneath the surface water that they emerge from.)

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The Sniff Test

1-30-19 red fox marking img_7153When your quest is to find out as much as you can about the identity, activity, diet and territory of your four-footed neighbors, it is logical to make the most of all your senses. Tracks can be seen, scrapings and bite marks on a tree can be felt and yes, one’s sense of smell can enhance any tracking expedition. Just as the tracks and scat of different species of animals have distinctive characteristics, so does the urine of different animals. Scent marking, including urination, is a behaviour used by animals to identify their territory, and therefore a highly visible sign in winter.

At this time of year, foxes are breeding, and without even putting your nose near where a fox has marked his territory with urine, you can detect its skunk-like odor as you pass by. If you’re so inclined (and I realize many readers may not be) you can heighten your sensory experience as well as your identification prowess by sampling the smell of other animals’ liquid waste. White-tailed deer urine has a pungent, piney smell, quite pleasing to this naturalist’s olfactory receptors. You can detect a porcupine den from a considerable distance by the pungent, very distinctive but hard to describe odor of its urine (which spills out onto and coats the bark of a tree den, thereby advertising the porcupine’s presence). Coyote urine smells very much like a domestic dog’s, and members of the weasel family often have musky-smelling urine, though a recently-sniffed fisher marking had very little scent.

Needless to say, it’s a lot easier to discover and sample urine when there’s snow on the ground and it is more evident. Virginia opossums, snowshoe hares, red and gray squirrels, eastern coyotes, red and gray foxes, raccoons, fishers, mink and striped skunks are all in or entering their breeding seasons, when scent marking is more frequent. Snow is currently on the ground, at least in northern New England. It’s prime time for olfactory activity, if you’re game. (Photo: stump marked by a red fox)

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Common Gartersnakes Brumating

1-28-19 gartersnake img_4888Somewhere between two and four feet (depending on where you live in New England) beneath our feet there is a “frost line” below which the ground water in soil doesn’t freeze. Snakes, being reptiles, are ectotherms, and their bodies assume the temperature of the air around them. In order to avoid being frozen to death in the winter, they retreat below the frost line, where they enter a state called brumation – the cold-blooded term for a state of torpor and inactivity that is not true hibernation, but in which a dramatic slowing down of bodily functions occurs. Crevices in south-facing rocky ledges and abandoned woodchuck, fox and skunk dens (and human cellars) often serve as hibernacula, or winter shelters. Common Gartersnakes are known to gather in large numbers (one Canadian den served as a hibernaculum for 8,000 gartersnakes), in order to concentrate the small amount of heat their bodies produce in the winter.

As the air temperature lowers in the fall, a snake’s body temperature falls and its metabolism decreases dramatically. Gartersnakes actively prepare for this by not eating for several weeks prior to hibernating. This allows all of the food they previously consumed to be completely broken down and absorbed into their system. To enhance this process, gartersnakes bask in the sun both before and during their early days of sheltering in hibernacula, warming themselves so as to increase the rate of their metabolism just prior to hibernating.

Should a snake happen to eat a large grasshopper, earthworm or small frog just prior to entering brumation, the snake may become extremely lethargic due to the slowing down of its metabolism, and the contents of its stomach may not be digested as quickly. The longer it takes to process food in its stomach, the greater the chances that this dead material will start to decay, which could result in serious illness to the snake.

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