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Archive for March, 2015

Meadow Vole Tunnels Exposed

3-31-15  meadow vole exposed tunnels IMG_3528If you live where the snow is actually melting, a labyrinth of vole tunnels may be revealing itself to you. These tunnels were excavated in the snow next to the ground in what is referred to as the subnivean layer. They lead from sleeping areas to known sources of food, and are advantageous to both mice and voles that travel in them – they provide thermal insulation by protecting them from the wind and cold, and they keep these rodents hidden from predators. Carbon dioxide, which builds up in the subnivean layer from animal respiration as well as CO₂ released from the ground, escapes through ventilation shafts, or air vents, that lead up to the surface of the snow.

Voles stay in these tunnels as long as the snow is deep enough not to expose them, finding food in the form of plants, seeds and bark from bushes and shrubs as they dig through the snow. This winter has provided voles, mice and shrews with an extended period of protection, as hungry barred owls attest to.

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Common Grackles Returning

3-30-15 common grackle 083Male Common Grackles have started to arrive on their northeastern breeding grounds (females will arrive in another week or so), having migrated from southern U.S. Common Grackles typically migrate in large flocks containing hundreds of birds, not all grackles. Red-winged Blackbirds, Brown-headed Cowbirds, European Starlings and occasionally American Robins can be found alongside Common Grackles in these migrating flocks. In the early 1990’s, magnetic material was found in the heads and necks of Common Grackles, indicating that the geomagnetic field may play a role in their migratory navigation.

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Juvenile Raccoons Dispersing & Adults Mating

3-27-15 raccoon tracks in snow IMG_5071When raccoons emerge from their communal (as many as 23 raccoons) winter dens, which they are doing now, the juveniles (those born last spring) disperse. Young males may travel as far as 170 miles, but usually establish their territories no further than 14 miles from their birth place. Juvenile females usually remain in their birth area, establishing a home range that either overlaps with or is included within the range of their mother. This time of year is also the peak of the breeding season for adult raccoons. Both males and females have multiple mates.

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White-winged Crossbills Nesting

White_winged crossbill by garth mcelroyrWhite-winged Crossbills inhabit the boreal forests of northern New England, the southern edge of their breeding grounds. This species, as well as Red Crossbills, are named for their bill which is supremely adapted to extracting seeds from conifer cones. Crossbills use their crossed bills to wedge open cone scales, after which they lift the seeds free with their tongues. Individuals can eat up to 3,000 conifer seeds per day.

White-winged Crossbills are erratic nesters that have been found breeding every month of the year. The birds nest whenever the available food supply is sufficient for egg formation and is likely to remain sufficient for at least three weeks, during the more energy demanding nestling stage.

Three nesting periods have been observed, each corresponding to the ripening of cones from different conifer species. The first season occurs in early July, when the cones of Tamarack, or American Larch, and White Spruce mature. The second nesting period begins in January and February, when they rely mainly on White and Red Spruce cone crops and the third season is starting now, as Black Spruce cones begin to open up. (Photo: public domain, male White-winged Crossbill)

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Porcupines Marking Dens

3-25-15 porcupine den IMG_9681Often, at this time of year, porcupines stake out their den trees (if they’re not inhabiting rocky ledges) by eating patches of inner bark, or cambium, with the exposed fresh inner wood announcing their occupancy. Typically, if a tree den is used year after year, they gnaw off a portion of bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells, indicating that this behavior is not for the purpose of obtaining nutrients. (photo: porcupine chewing near hollow tree den entrance)

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Owls & Humans Share Trait

barred owl 194Birds have three eyelids – an upper eyelid, lower eyelid and a third semitransparent membrane called a nictitating membrane that sweeps across the eye much like a windshield wiper. This membrane keeps their eyes moist, and protects their corneas from being scratched.

In most birds, including owls, the upper and lower eyelids are used to close the eyes when sleeping, and the nictitating membrane is used for blinking. Humans close their eyes mainly by lowering the upper eyelid, where most birds do so by raising the lower lid. Owls (and a few other birds such as parrots, toucans, wrens and ostriches) are more human-like in that their upper lids are usually lowered to close their eyes. Owls also usually close their eyes, partly or entirely, when capturing and transferring prey, scratching their face, preening another owl and copulating. (Note the rows of feathers on this barred owl’s upper eyelids.)

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Eastern Chipmunks Up & Active

3-23-15  eastern chipmunk IMG_2146Eastern chipmunks typically emerge above ground in late March, at a time when most mature females are in breeding condition. It takes little time for nearby males to come courting. During their breeding period, females, for the most part, remain within their territory, whereas males explore within and outside of their territories in search of a receptive female.

Male suitors congregate on the site of a female in estrus and work out the hierarchy within the group. The top chipmunk wins the opportunity to breed with the female. During these dominance battles, the males vocalize, wave their upright tails from side to side, chase each other and fight. The dominant male then breeds with the female. She proceeds to mate anywhere from 10 to 30 times within about a six to seven-hour receptive period, not necessarily with the same male. All of this activity takes place within a week of when chipmunks come above ground, so keep your eyes peeled for those waving tails.

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Accommodating Both Birds & Bears

3-20 - birds and bears comment IMG_8628In response to my “bears & bird feeders” blog yesterday, a highly respected New England naturalist responded with the following comment, suggesting several ways to have your cake and eat it too. I so endorse his ideas, and especially the reasons behind them, that I am sharing them with my blog readers today.

April to mid- May is perhaps the most food-limited time for birds too. Furthermore, it is my belief that the biggest share of future curious naturalists (and conservationists) are those that grow up in households that feed birds. We NEED those bird feeders out there too! We naturalist types should be thinking about how to bear up and still keep the feeders going. Most of the time, I find that bringing the feeders inside for the night in late afternoon “works”. (I say, like bringing in the cat or the chickens.) We have a “bear resistant” rig here at the Harris Center-a feeding station that is raised and lowered like a flag on a two story flag pole. I know others have found electronic ways of keeping bears away (like motion activated lights), and my friends and neighbors Don and Lilian Stokes are very successful by electrifying their feeding station-just like an apiary. They wish many more people would do so.
Meade Cadot, Naturalist Emeritus, Harris Center for Conservation Education


Time To Take Down Bird Feeders

3-17-15 black bear-eating sunflower seeds  IMG_3607To prevent black bears from visiting backyard bird feeders, Fish & Wildlife Departments in New England recommend taking down birdfeeders from April 1st through December 1st. This year those dates are fairly conservative, as bears were visiting feeders after December 1st, and several have been seen frequenting feeders this month. The idea is to remove anything outdoors that would be of any interest to a bear which has just emerged from hibernation and is desperate for food.

Approximately 85% of a bear’s diet is vegetation. Before green shoots make an appearance in the spring, flower parts of aspen, willow, maple, ash and hazelnut, along with carrion, make up most of a bear’s diet. After losing 23% of its body weight during hibernation, a black bear finds protein-packed sunflower seeds very appealing. Make sure your garbage is secured, barbeques clean and pet food kept indoors, as well as your feeders. Keeping bears away not only prevents property from being damaged, but it also prevents bears from becoming nuisance animals that are habituated to food associated with humans, which often leads to the end of a bear’s life.

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Mourning Doves Calling

3-19-15 -mourning dove IMG_2091The mournful lament of the male mourning dove is often one of the first songs heard in the early spring. The frequency of this call builds to a peak from mid-May to mid-June. As in many other pigeons and doves, the Mourning Dove’s main call, or “perch coo” (coo-oo, OO, OO, OO) is an advertising call, sung in order to attract a mate. Unmated males often establish perches within their territory from which they repeatedly sing.

A shorter nest call is used by a paired male to attract his mate to a potential nest site. The male then gathers nesting material and presents it to the female while standing on her back. While she constructs the nest, he continues to use the nest call to maintain a bond with his mate. Once the nest is built, this call diminishes. You can hear Mourning Dove calls at http://www.allaboutbirds.org/guide/mourning_dove/sounds, although to my ear, it’s hard to distinguish the perch call from the nest call in these recordings.

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Rodents Recycling

3-13-15  gray squirrel 001Bones, antlers, skulls, turtle shells – all are recycled relatively quickly by rodents seeking a source of minerals, particularly calcium and phosphorus. All rodents possess four incisors, two in the front of the upper jaw and two opposite these, on the bottom jaw. These incisors, unlike other teeth, never stop growing. By gnawing on hard objects such as bones, rodents keep their incisors paired down. If an incisor is broken or lost, the opposing incisor will continue growing in a circle, having nothing to grind against, causing the rodent to die of starvation or from having its brain pierced (through the roof of the rodent’s mouth) by the ever-growing incisor. In this photograph, a gray squirrel is obtaining minerals and sharpening its incisors on a moose skull that a human wedged into the crotch of a tree.

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Male American Goldfinch’s Seasonal Plumage

3-17-15  male American goldfinch IMG_0482Most songbirds have one complete molt every year, in the late summer. Some, like the American goldfinch, have another (partial) molt in the spring. Last fall male goldfinches molted, replacing many of their bright yellow feathers with drab, greenish-gray feathers, so that they closely resemble females during the winter. Goldfinches start their partial molt in February, and in the next month or two, males will once again become bright yellow beacons. No-one can illustrate the subtle seasonal plumage changes of a male American goldfinch better than David Sibley: http://www.sibleyguides.com/2012/05/the-annual-plumage-cycle-of-a-male-american-goldfinch/ (Photo: male American goldfinch in March)

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Red Foxes Locating Prey

OLYMPUS DIGITAL CAMERADeep snow certainly presents challenges to predators – their prey is well hidden for the most part, and if they are to survive, they must compensate for not being able to see what they are hunting. Foxes are an example of how a predator survives in a winter like the Northeast has had. A red fox hunting for food is constantly listening for the sound of rodent feet under the snow, and when it hears them (they can hear a mouse or vole three feet beneath the surface of the snow) they leap up into the air and pounce on or near their prey with their front feet. Most of the time they are not successful, and come up empty-mouthed, but they usually succeed often enough to survive. Biologists are still working on understanding exactly how they do this.

Researchers in Czechoslovakia, watching foxes hunt in the wild, determined that a fox’s success seems to correlate with the direction in which it jumps. If the observed foxes jumped to the northeast they killed on 73 % of their attacks. If they reversed direction and jumped exactly the opposite way, they killed 60 % of the time. But in all other directions — east, south, west, or variations thereof— they were successful only 18% of the time. Jaroslav Cerveny, the Czech researcher, feels that foxes have a “magnetic sense,” and are capable of lining up the rodent sounds that reach their ears with the slope of the Earth’s magnetic field, and when this occurs, dinner is usually caught. (This theory has yet to be confirmed, but the likelihood that it is correct is great.) (Photo by Susan Holland, in the wilds of northwest Ontario)

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Black-capped Chickadees Starting to Build Nests

3-13-15  black-capped chickadee and Emma's hair 067At least two to four weeks before one would expect to find a black-capped chickadee building a nest, one was busily collecting hairs shed by my chocolate lab yesterday. In addition to fur, chickadees line their nest with grass (not available yet here), down and moss (hard to come by with two feet of snow still on the ground). Chickadees are able to nest this early in part because they nest in cavities, which offer them protection from the elements. Not having bills strong enough to hammer out cavities in living trees, chickadees rely heavily on rotting stumps for nest sites — the wood in them is punky and easy to remove. Birch, poplar and sugar maple snags and stumps are preferred nesting trees. If you want to provide chickadees and other birds with nesting material, take advantage of the fact that dogs and cats are shedding now, and recycle their fur.

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White-tailed Deer Scraping Bark

3-3-15  deer scraping2IMG_0490During the winter, white-tailed deer browse on the twigs, buds and bark of trees. Deer have incisors in the front of their bottom jaw, but none in the front of their top jaw, just a hard palate. They grip the bark with their bottom front incisors and scrape their jaw upwards, leaving behind grooves the width of their bottom incisors. Often there are frayed ends of bark at the top end of the groove, due to the deer having to use its hard palate and incisors, rather than two sets of incisors, to separate the bark from the tree. Favorite trees include red and striped maples, oaks, poplar, pines, hemlock, arborvitae and balsam fir.

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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.)

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Returning Red-winged Blackbirds Announce the Arrival of Spring

3-10-15  red-winged blackbird IMG_3155Regardless of the deep snow that remains on the ground and the frigid temperatures we’ve had recently, spring has announced itself with the arrival of red-winged blackbirds this week. Most redwings that breed in New England migrate approximately 500 miles further south to spend the winter. In the spring, males begin migrating first, flying north in flocks during the day to their breeding grounds. (In the fall, females depart first.) While they eat primarily insects during the breeding season, redwings subsist mainly on seeds and grain this early in the season. Before you know it, females will return, and up to fifteen of them will be nesting on the territory of each male (though he doesn’t sire all of the nestlings).

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Exposed Honeybee Colony

honeycomb IMG_5036In the Northeast, honeybees typically choose a protected site such as a hollow tree in which to build their hive. Harsh winters demand this protection. Infrequently you will see where an attempt has been made to survive the elements without anything to contain the heat that the honeybees produce by shivering, or to block the wind, snow or sleet. Inevitably, this far north, the colony does not survive the winter.

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Porcupine Cecum

3-6-15 porcupine2 IMG_5163Your guesses were outstanding – especially “Pinocchio scat” and “petrified baby hippopotamus”– and a couple of readers even nailed it: part of the intestines of a porcupine. (Many of you suggested it might be a black bear’s fecal plug – not a bad guess – though any bear that had to pass something this large when it woke up might decide to hibernate year round.)

Mystery Photo Explanation: A fisher killed and ate a porcupine, choosing not to eat (and leaving behind) a portion of the porcupine’s digestive tract called a cecum – a sac located between the large and small intestine where the cellulose in leaves and bark that a porcupine eats are broken down.

During the warmer seasons of the year, porcupines feed on sugar maple buds, leaves of basswood, aspen and beech saplings, grasses and other herbaceous plants, apples, acorns and beech nuts. In winter, their diet consists mostly of leaves (mainly eastern hemlock in the Northeast), which contain low levels of nutrients and high levels of dietary fiber. Certain mammals and birds possess specific bacteria that secrete enzymes capable of digesting the cellulose in fiber (beavers, hares, rabbits and ruffed grouse come to mind) through the process of fermentation. Because these enzymes work slowly, the digestive tract of a porcupine is very long (26% of a porcupine’s total weight) and the fiber passes through it slowly.

A majority of the bacterial activity in a porcupine’s digestive system takes place in the cecum, which is about the same size as a porcupine’s stomach. Here fermentation turns finely ground woody material into molecules small enough to be absorbed by the porcupine’s body. (A process referred to as “hind gut fermentation.”) Research shows that 16% of a porcupine’s energy requirements are supplied by the porcupine’s cecal fermentation.

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Mystery Photo

mystery photo 154This frozen object was discovered in mixed woods, on top of the snow. Hint: it measures between 6 and 7 inches long, and is about 4 inches wide. It weighs approximately one pound and contains tiny wood fibers. All guesses welcome under “comments.”

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Otter Tracks

3-3-15 otter tracks IMG_5843North American River Otters have four webbed feet and strong claws that assist them in water as well as on land. There is relatively little hair on the soles of otter feet, and therefore the individual pads are often well defined in good tracking snow. Each foot leaves a five-toed track, with the inside toe on the front feet being somewhat smaller than the others. Otters have four plantar pad glands in the center of each hind foot with which they mark mounds of vegetation they create.

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Pileated Woodpecker Feeding Hole Embellishment

3-2-15  pileated horizontal lines 057Large rectangular excavations in trees, indicating Pileated Woodpecker feeding activity, are relatively common. These holes give the woodpecker access to carpenter ants living in galleries within the tree. What are not common are the horizontal lines radiating out from either side of the top rectangular Pileated Woodpecker feeding hole (and, more subtly, the bottom two holes) in the pictured tree.

Pileated Woodpeckers use methods other than drilling rectangular holes to locate insects – they glean branches, trunks and logs, peck bark and scale bark off of trees. But these lines are unusual, to say the least. If anyone is familiar with this pattern, and would care to explain the function of these horizontal lines, it would be greatly appreciated. After racking my brain and checking several resources, I cannot come up with a plausible explanation, though inevitably there has to be one, for no pileated woodpecker, or any other creature, is about to waste precious energy, especially in a winter as cold as this one. (Thanks to photographer, naturalist and keen-eyed John Snell (http://stilllearningtosee.com/about/) for finding and sharing this discovery with Naturally Curious.)

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