Ruffed Grouse Make Do With Shallow Soft Snow Depth
There are about five or six inches of new powdery snow on top of an icy crust in parts of central Vermont now, with more to come soon. It is common knowledge that ten inches of snow are necessary for Ruffed Grouse to dive into and burrow under the snow in order to make an insulating nocturnal snow roost. With only five inches of snow, a grouse still seeks shelter, but somehow it knows not to dive into the snow from the air. Rather, it lands on the surface of the snow, and then walks along making a groove in the snow as it goes, until it decides to rest for the night.
Several such resting spots were apparent today at the base of trees — slight depressions fully exposed. The grouse that made the snow roost in this photograph shuffled through the snow and then scrunched down without breaking the surface of the snow where it settled for the night, so that it had an inch or two of snow over its body – hiding it from predators, if not providing much insulation. In the morning, after defecating, it departed, not bursting out of a snow bank as it would if there were a lot of snow, but instead lifting off in plain view, leaving faint wing prints on the surface of the snow.
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Coyotes Mating
Coyotes mate in January and February, but pre-mating behavior started two to three months ago. During this period scent marking increases, as does howling, and males wander far and wide. Female coyotes come into heat only once a year. When this happens, and two coyotes pair up, they may howl in a duet before mating. If there is an ample food supply, most females will breed and between 60% and 90% of adult females will produce a litter. The size of the litter fluctuates with the size of the rodent population; lots of rodents means larger litters. The same pair of coyotes may mate from year to year, but not necessarily for life. (Photo taken at Squam Lakes Natural Science Center)
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Mourning Dove Diet
Seeds, including cultivated grains, grasses, weeds and berries, make up 99 percent of a Mourning Dove’s diet. Because they can find enough food to sustain themselves, Mourning Doves are permanent residents, remaining year round, even in northern New England.
These birds feed on the ground and in the open, consuming 12 to 20 percent of their body weight per day, or 71 calories on average. Mourning Doves swallow the seeds and store them in an enlargement of the esophagus called a crop. Once their crop is filled (the record is 17,200 bluegrass seeds in a single crop), they can then fly to a protected area where they can safely digest their food.
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Meadow Vole Tracks
Meadow voles and mice (white-footed and deer) leave most of the tiny tracks one sees on the surface of the snow. In deep snow, meadow voles tend to remain beneath the surface in tunnels, but occasionally do travel on top of the snow. Typically, a white-footed or deer mouse leaves a leaping, four-print pattern, often with a tail drag mark running between the sets of prints. A leaping meadow vole may or may not leave a tail mark and usually has paired prints. However, voles leave a variety of tracks patterns, depending on the speed at which they are traveling and the depth of the snow, so they can be confusing.
Although one might think that three different animals made the tracks in this photograph, every tunnel, track and hole was made by a meadow vole. The trail in the lower left was made by a trotting vole, the tunnel on the right was exposed because the layer of crust just under the new snow prevented the vole from going any deeper, and at the top, the vole was quickly bounding into the safety of its deeper tunnel.
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Common Redpolls Appearing
The birds most commonly associated with winter irruptions are the winter finches — Pine Grosbeak, Red Crossbill, White-winged Crossbill, Purple Finch, Pine Siskin, Common Redpoll, and Evening Grosbeak. Their food supply, or lack thereof, in the Canadian boreal forests where they normally overwinter, determines whether or not they will be seen as far south as the U. S. Key trees affecting finch movements in the boreal forest are spruces, birches and mountain-ashes.
Common Redpolls feed primarily on the catkins (seed-containing fruit) produced by birch and alder trees. When catkin production is low further north, as it is this winter, Common Redpolls leave these areas and irrupt into areas where food is more plentiful. (Photo: male Common Redpoll)
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Great Horned Owl Live Cam
A Naturally Curious blog reader just made me aware of this Great Horned Owl live cam in Georgia, where Great Horned Owls are now nesting.
Great Horned Owls Courting
The intense hooting of Great Horned Owls begins in late December or early January, about a month before actual mating takes place. Males call during most seasons of the year, but the period when the males are hooting vigorously lasts for a month or six weeks. During the mating season the deep, rich tones of the males are occasionally interspersed with the higher and huskier notes of the females. The answering calls of the females are heard for only a week or two, toward the end of the six-week period.
Eventually, when a male and female approach each other, they do a sort of courtship “dance.” The male cocks his tail, swells his white bib (see photo), and with much bobbing and jerking utters a series of deep sonorous calls that elicit calling responses by the female. He cautiously approaches the female, continuing much tail-bobbing and posturing. The owls nod, bow, and spread their wings as well as shake their heads. Courting pairs have been observed engaging in high-pitched giggling, screaming, and bill-snapping. Mutual bill rubbing and preening also occurs. Copulation concludes the courtship ritual, with both owls hooting at a rate of 4 or 5 hoots per second throughout copulation, which lasts 4 – 7 seconds. (Photo: Great Horned Owl, in captivity)
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Fisher Scat
For seekers of animal signs, tracking a fisher is a most rewarding endeavor. Fishers are constantly marking their territory – rolling on and breaking limbs of conifer saplings as well as urinating and defecating on or near saplings or on prominent, elevated stumps or rocks.
More than other members of the weasel family, Fishers can control the amount of scat they deposit, so that there can be a minuscule amount, or a full-size scat (2” – 7” long). Perhaps because of their predilection for marking with their scat frequently, they often use this medium sparingly.
The color of Fisher scat is usually dark brown or black, but once in a great while one happens upon fisher scat that is bright orange – a sure sign that the fisher has lived up to its aquatic name and has dined on crayfish in the recent past. Fishers primarily prey on snowshoe hares, porcupines, ground-nesting birds and smaller rodents. However, they do frequent streams that remain open in the winter, where they hunt for crayfish and, very rarely, fish.
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A Bobcat’s White-tailed Deer Cache
Rabbits and hares comprise much of a Bobcat’s diet, but when prey is scarce or hard to capture, adult male or sometimes large adult female Bobcats will attack bedded, weak or injured adult White-tailed Deer. Bobcats often cache prey (such as a deer) that is too large to eat in one feeding, returning to feed on it for an extended period of time. They scrape up leaves, bark, twigs, soil. snow – whatever is available – and cover their prey. When feeding on a deer, Bobcats bite away the hair to avoid eating it, and this discarded hair is frequently mixed with the debris that the cat drags over the kill to cover it (see main photo – taken the day after the deer was cached), or is left windblown around the carcass. A characteristic sign of Bobcat feeding is the amount of hair strewn around the carcass and the lack of broken long bones (Bobcats don’t have the strength to break them with their teeth).
Typically a Bobcat rests near its cache to protect it, but it doesn’t take long for other animals to detect and take advantage of an easy meal. Within three days of this deer being cached, Coyotes and Common Ravens had discovered it, and both they and the Bobcat had eaten enough of it to expose the deer’s rib cage (see insert).
Other predators that occasionally cache and cover their kills include Mountain Lions, Black Bears and Fishers. Large caches found in the winter in the Northeast are likely to belong to a Bobcat or Fisher (Fishers typically cache and feed on deer that they find as carrion).
(Cache discovered by Lynn & Otto Wurzburg, who observed the Bobcat leaving after caching the deer; photograph by Lynn Wurzburg)
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Lapland Longspur Plumage
The Lapland Longspur, named for the unusually long claw on its hind foot, breeds in the Arctic tundra and overwinters near fields throughout the northern half of the U.S. in flocks numbering up to four million birds.
Lapland Longspurs have two distinctly different plumages, especially the males. Their winter plumage (see photo) is streaked brown and somewhat dull. However, in the summer, the male’s plumage is very dramatic (see insert). The back of his neck, or nape, is bright rufous orange and black feathers form a distinctive facial mask and bib, bordered by a white stripe.
Unlike most birds with different breeding and non-breeding plumages, longspurs molt only once per year, in the fall, into their non-breeding plumage. How can the males look so different in the breeding season if there isn’t a second molt? By spring, the outer tips of these feathers have worn off to reveal the males’ (and females’, but to a lesser degree) distinctive breeding plumage underneath. (Insert photo from public domain)
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The Effects of An Icy Crust on Wildlife
This winter has brought us several storms that have ended in rain and were followed by plummeting temperatures. Just a few inches down into the powdery snow on top of the ground there is a ¼”-thick crust, and if you dig down several more inches, there is a second layer of ice, roughly 1/8”-thick. When a thick, icy layer of crust forms, it can have a dramatic effect on the lives of wildlife both above and below it.
Some animals are relatively unaffected by the presence of a crust but many predators and prey are significantly helped or hindered by it. Ruffed grouse cannot seek overnight shelter from the bitter cold and/or predators by diving into a foot of soft snow and creating a snow cave (see photo). On the other hand, small rodents have a distinct advantage — mice and voles have several layers of ice between themselves and hungry coyotes, foxes and owls. Snowshoe hares lose the advantage they usually have on deep, soft snow — “snowshoes” that keep them on top of the snow when the bobcat or fisher chasing them has to flounder through it. Turkeys don’t have the strength to dig down through one thick crust, much less two or more, in order to reach hidden acorns. If a deer is being chased, its pointed hooves will break through the crust, slowing the deer down, whereas the crust may well support a lighter predator, allowing it to outrun the deer. Red squirrels have to work much harder to reach their cached winter cones and to create tunnels.
What is a mere inconvenience to us humans literally is costing as well as saving the lives of wildlife this winter.
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Bobcats Scent Marking
Like most cats, the bobcat is territorial and largely solitary. There is some overlap of males’ home ranges and they use several methods to mark territorial boundaries and to communicate with other bobcats. The signs of these methods include claw marks on trees, scrapes (mounds of soil and leaves scraped with the bobcat’s hind feet and formed into a pile that is marked with urine or scat), deposits of urine or feces and secretions from both mouth and anal glands.
Scat is frequently found in the same location, usually in conspicuous areas along travel routes, or near a den. (One monitored marking site contained 254 bobcat scats.) Resident bobcats also scent-mark with urine (one to five or more scent marks per mile) , squirting small amounts on rocks, bushes and snow banks as they travel. These scent markings function as biological bulletin boards within and between home ranges. In addition to marking territory, the scent markings are a means by which female bobcats claim a den, transient bobcats avoid resident bobcats, and bobcats find a mate.
When a bobcat encounters the scent mark of another bobcat, it raises its head with its mouth half open, nostrils closed and upper lip slightly curled back. This behavior is called the flehmen response. The bobcat inhales the scent into its mouth, where its vomeronasal organ detects molecules of the marker’s pheromones, which helps identify the marker and indicates, if it’s a female in estrus, whether or not she is ready to mate.
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Aquatic Frogs Hibernating in Ponds
Most aquatic frogs such as this Green Frog have been deep in hibernation for several months. A common misconception is that frogs spend the winter the way aquatic turtles do, dug into the mud at the bottom of a pond or stream. In fact, hibernating frogs would suffocate if they dug into the mud for an extended period of time. A hibernating turtle’s metabolism slows down so drastically that it can get by on the mud’s meager oxygen supply. Hibernating aquatic frogs, however, must be near oxygen-rich water and spend a good portion of the winter just lying on top of the mud or only partially buried. They may even slowly swim around from time to time.
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Snowshoe Hare Succumbs to Avian Predator
The drama that goes on in our woodlands is never-ending, and winter provides us with a window into life and death scenarios. One of the most sought-after prey animals in northern New England is the snowshoe hare. Bobcats, lynxes, coyotes, foxes and fishers are some of the mammalian predators of this lagomorph. In this particular case, however, the predator had wings (determined by wing imprints in the snow and lack of tracks). While great horned owls do prey on hares, there was a tell-tale sign that it was a hawk, not an owl, which produced this pile of fur and bones. If you look to the upper left of the photograph, and to the upper right, you will see lengthy curved lines of bird droppings, or sprays, that were left by the predator as it plucked its prey. Because it was ejected forcibly, and didn’t just drop down on the snow where the bird was situated, the scat leads one to the conclusion that it was a hawk, not an owl, which deposited it. A woodland accipiter capable of capturing a snowshoe hare after an extensive chase, which this was, is the northern goshawk. (Thanks to Nicole Cormen for photo op.)
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Crabapple Consumers
Even without much of anything to go on, all answers were correct! Although Cedar Waxwings were the predominant avian visitor to this crab apple tree when I visited it, there were also robins, starlings and crows feasting away (and presumably several other species, including turkeys, as some of you guessed, at other times).
Cedar Waxwings are among the most frugivorous (fruit-eating) birds in North America. In the winter, sugary fruits dominate their diet to such a degree that occasionally, when the fruit has become overripe and has started to ferment and produce alcohol, the waxwings can become intoxicated and, rarely, die. One individual saw that her front lawn was littered with the bodies of dead Cedar Waxwings on top of the snow, but by the time she went out to dispose of them, the drunken birds had all revived and flown away.
During the winter, Cedar Waxwings travel in flocks of up to several hundred birds. They are nomadic, roaming the countryside in search of crab apples, hawthorns and mountain ashes, as well as serviceberry, juniper, winterberry, dogwood and cedar, among others. Waxwings will descend upon a tree en masse and while perched will bend down and pluck crab apple after crab apple, swallowing them whole, one at a time. Occasionally you will see them hovering briefly in the air while plucking fruit. They are well known for “gifting” fruit to fellow waxwings.
Many birds that eat a lot of fruit separate out the seeds and then regurgitate them. Cedar Waxwings let the seeds pass through them, scarifying the seeds in their digestive tract (breaking down their outer seed coat), which, once the seeds are deposited, allows them to eventually germinate. Because of this, waxwings are considered important seed dispersers for many fruiting plants in North America (including the invasive, non-native honeysuckle which, when eaten during the time feathers are developing, causes Cedar Waxwings to develop orange, not yellow, tail bands).
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Mystery Photo
Who’s been here? Hint: This photograph was taken under a crab apple tree. Mystery will be solved in tomorrow’s post.
Cold Snaps & Invasive Insects
(Our recent plummeting temperatures in the Northeast convinced me to re-post this in an effort to see a silver lining.)
There can be a plus side to the sub-zero temperatures New England experiences in winter – the cold weather may well decrease the number of invasive pests we have. An example of this is the Hemlock Woolly Adelgid (the aphid-like introduced insect decimating the eastern hemlock population) which succumbs at 4 or 5 degrees F. However, some insects are not fazed by the cold until it dips way below zero. At -20 F., roughly half of the Emerald Ash Borer larvae (an invasive beetle that is highly destructive to ash trees) overwintering in trees will die. Once the temperature reaches -30 F., there’s a 90 percent mortality rate. Bed Bugs face instant death at -22 degrees F., but it takes 24 hours to kill them at -11 degrees F. and 72 hours to kill them at 0 degrees F.
Unfortunately, once an invasive insect establishes itself, even if its numbers go way down for whatever reason, it usually rebounds in several years’ time. Some invertebrates are not affected by the cold temperatures. The Black-legged (Deer) Ticks that reside on moose, deer, mice, birds and other hosts can withstand sub-zero temperatures as they have the warmth of their hosts’ bodies to keep them warm. In order for ticks to succumb to the cold, the frigid air has to last until May, when the fertilized female ticks fall off their hosts to lay their eggs. (photo – emerald ash borer, public domain image)
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Porcupine Feet Designed for Climbing
Porcupines spend a lot of their life climbing on and clinging to trees due to their woody diet. In addition to strong, curved nails that fit into bark crevices, the soles of their feet have a pebbly surface with very little fur. The bumpy texture increases the surface area and the friction when a porcupine’s feet are in contact with a branch, helping the porcupine hold onto the tree trunk and branches. Even so, examination of porcupine skeletons confirms that many have fractures that have healed, indicating that a significant number of porcupines, while their bodies are adapted for climbing, still experience falls during their lifetime. (Photos: porcupine footpad; insert – porcupine footpad in fisher scat)
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Sedge Seeds
Over 500 species of sedges in the genus Carex are found in the U.S. – over half of the world’s total. The great majority of these perennial, grass-like plants grow in the moist soil of meadows, marshes and bogs, as well as in high altitudes. Sedges are often distinguished from grasses by their stem, which is typically triangular in cross-section (“sedges have edges”). The flowers of sedges, each surrounded by a bottle-shaped bract, or modified leaf called a perigynium, are clustered on spikelets. The tips of these bracts persist after the seeds have formed, giving the spikelets a prickly appearance.
Because of their wide availability, the seeds are eaten by many kinds of wildlife, especially birds. Wild Turkeys, American Woodcock, Northern Cardinals, Horned Larks, Snow Buntings, Lapland Longspurs, ducks, rails, sparrows, redpolls and finches relish them. In the Northeast, Carex seeds, along with insects, are the most regular items in the diet of Ruffed Grouse chicks. Moose also occasionally feed on sedge seeds. (Photo: Longhair or Bottlebrush Sedge, Carex comosa)
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Owl Night Vision
Like humans, birds have a sensitive retina in the back of their eyes that absorbs incoming light, senses it, integrates the information in it, and sends this information on to their brain. An avian retina is much thicker than ours and contains more rod cells (for dim light vision) and cone cells (for acuity and color vision).
As most owls are active at night, their eyes must be very efficient at collecting and processing light. The eyes of owls are disproportionately large compared to the size of their skull, and enable them to collect as much light as possible. In addition, the retina of an owl’s eye has an abundance of light-sensitive rod cells — owls have almost a million rods per square millimeter compared to humans which have only about 200,000. Barn owls can see a mouse at 6 – 7 feet with an illumination of .00000073 foot-candles – the equivalent of humans seeing a mouse by the light of a match a mile away. Eye size, an abundance of rod cells and additional neural mechanisms provide owls with vision greater than that of most of their prey.
Since owls have extraordinary night vision, it is often thought that they are blind in strong light. This is not true, because their pupils have a wide range of adjustment, allowing the right amount of light to strike the retina. Some species of owls can actually see better than humans in bright light. (Photo: barn owl, in captivity)
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Ice-coated Tree Buds
Recently freezing rain coated trees with ice and the sight reminded me that when a freeze is threatening fruit trees in the spring, just as buds are breaking, orchardists often opt to replicate this phenomenon by starting a sprinkler and coating their trees with ice. Flower buds that are starting to open can be extremely temperature sensitive, suffering damage when it goes below freezing even temporarily. As counter-intuitive as it seems, a properly maintained layer of ice works well to protect opening buds from the cold. When water freezes, heat is produced at a rate of 80 calories per gram of water (the heat of fusion). If water is continually applied to the tree and consistently freezes, it is possible to maintain the buds around 32 degrees F., thereby protecting the flowers within them. (Photo- sugar maple terminal buds)
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Hooded Mergansers Seek Open Water
Hooded Mergansers are short-distance migrants that can be found in eastern North America year round where ponds and rivers remain open and slow-moving fish, insects and crayfish are plentiful. Some individuals migrate south and southwest in winter — 80% of birds banded in Maine, Vermont, New Hampshire and New York were recovered in coastal Atlantic states from New Jersey to Florida. A smaller number actually migrate north to spend winters in the Great Lakes and southern Canada. While numbers swell in March/April and November in northern New England due to migration, if there is open water you may well see Hooded Mergansers this far north throughout the winter.
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