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Archive for April, 2013

Beaver Scent Mounds

4-30-13 beaver scent moundsThis is the time of year when two-year-old beavers leave their lodges and strike out on their own, primarily because the woods surrounding a pond usually can’t support more than one family of beavers. Beavers are exceptionally territorial; once they’ve established a lodge, they do not take kindly to interlopers. In order to make this perfectly clear to house-hunting young beavers, in the spring resident beavers build what are called scent mounds — piles (up to three feet in height, but usually much smaller) of mud, leaves and pond-bottom debris — around the perimeter of their territory. They then smear castoreum, a substance that comes from their castor sacs, over the mound. Chemicals in the castoreum convey to roaming young beavers that this particular pond is spoken for.


Spring Peepers Mating & Laying Eggs

spring peepers mating DA8A0504The mating season for spring peepers lasts two months or more, and judging from the sound that is coming from ponds and woodlands these days and nights, it is in full swing. Once a singing male is successful in attracting a female, he mounts and clasps her while depositing his sperm on her eggs. She lays up to 800 eggs, either singly or in small groups, on plants within the male’s territory. The frogs remain joined (a position known as “amplexus”) for up to four hours. After egg-laying and fertilization is completed, the female peeper returns to the woods; the male remains at the pond and resumes singing.


Six- and Twelve-spotted Tiger Beetles Active

4-25-13 6 and 12-spotted tiger beetlesTiger beetles (named for their ferocity) can be easily recognized by their quick, jerky movements, huge eyes and large, multiple mandibles. Look for these voracious hunters in sunny, open spots where they can easily spot prey and potential predators. The six-spotted tiger beetle is hard to miss, thanks to its iridescent green outer wings, or elytra. Contrary to that which its name implies, this species can have five, two or even no white spots. It is most likely to be found on exposed rocks, logs and tree trunks, whereas the twelve-spotted (may have 12 or fewer spots) tiger beetle tends to prefer moist sandy spots. They both capture and liquefy their prey by masticating it with their formidable mandibles, squeezing it and swallowing the juice. Both of these species of tiger beetles have a two year life cycle, overwintering as adults their first winter, emerging early in the spring, mating and laying eggs during the summer and then overwintering as larvae.


Great Blue Herons Mating

4-22-13 great blue herons copulating2  IMG_8954Numerous displays lead up to the mating of great blue herons – neck stretching, bill clacking, wing preening, circling flights, twig shaking, crest raising, neck fluffing, to name but a few. After this elaborate courtship comes copulation, which is not nearly as showy. Copulation typically takes place on the nest. The male places one foot gently in the center of the female’s back. The female leans forward, bends her ankles and holds her wings slightly away from her sides while the male lowers himself, often flapping his wings. Once the job is done, the male flies off. If you look closely you can perhaps make out that the male is grasping the female’s head/neck while copulation takes place.


Eastern Chipmunks Soon to Give Birth

4-24-13 dirty eastern chipmunk IMG_3051It’s possible that this chipmunk is preparing a nesting chamber in her underground burrow, judging from the amount of dirt that is on her. Sometime between February and early April chipmunks mate. Roughly a month later they give birth to 3 to 5 young in a bulky nest of leaves inside a 24” x 15” x 10” chamber. Within a week, hair and stripes will be evident on the young chipmunks. In about a month, they will venture out of the burrow, looking like small adults.


Eastern Commas Flying

4-23-13 green comma IMG_9353Commas are a group of butterflies also known as anglewings (for obvious reasons). There are several species of commas in New England, all of which have a silver mark in the shape of a comma underneath each hind wing. Like mourning cloaks, these butterflies overwinter as adults in bark crevices, logs or other protected spots. You often see them in the woods, where they feed on tree sap, mud, scat and decaying organic matter. When perched with their wings closed, they are extremely well camouflaged and easily mistaken for a dead leaf.


Porcupines Giving Birth

4-18-13 porcupine IMG_9203It’s not easy being a female porcupine. You mate in the fall and are either pregnant (7 months) or lactating (4 months) for the next 11 months before you have one month’s break and begin this cycle all over again. This time of year porcupines are giving birth to one young that is covered in fur and quills and weighs about a pound. The young porcupette is born headfirst in a sac, in order to protect the mother from quill damage. Its quills are soft at birth, but harden within an hour. (Thanks to Kay and Peter Shumway for photo op.)


Hepatica Blooming

4-18-13 hepatica DA8A9542Hepatica has finally opened its hairy buds and greeted the world with its beautiful white, pink, blue and lavender blossoms. Typically the only wildflowers to appear earlier than this member of the Buttercup family are skunk cabbage and coltsfoot. Like many flowers, hepatica blossoms open on sunny days, and close at night and on cloudy days. This prevents rain from washing out the pollen and nectar which help attract pollinating insects, including early-flying bees and flies.


Foraging Technique of American Robins

4-17-13 A. robin2 IMG_8800In the fall and winter, fruit makes up about 90% of an American robin’s diet. In the spring, only 10% of a robin’s diet consists of fruit; invertebrates make up the remaining 90%. (Summer is a fairly even mixture of both.) At this time of year, earthworms are a popular food item with robins. Watching a robin foraging for a worm can make you wonder whether the robin is using its ears or its eyes to locate the worm. It turns out that most worms are seen, not heard, by robins. Because the sound of worms burrowing in the soil is of low intensity, they usually cannot be heard by robins because of background noise. Using sight, not sound, the robin first aims one eye toward a spot on the ground in front of it, and after holding this position for a few seconds, rotates its head and draws a bead with its other eye on the same spot– an earthworm in its burrow. The robin then quickly thrusts its bill into the burrow in an attempt to get its next meal.


Frog Vocal Sacs

4-16-13  vocal sacs“Peeps” and “quacks” fill the air these days.  How is it that these frog calls travel so far?  It’s all thanks to a thin membrane , or sac, that most frogs have. Note the single inflated sac of the spring peeper, and the paired sacs on either side of the wood frog’s head. These vocal sacs act as resonating chambers, causing the male frog’s mating call to be amplified and carried far (some species of frogs can be heard over half a mile away). Most frogs have one of three basic types of vocal sacs: a single throat sac (the most common), paired throat sacs (partially separated by connective tissue) and paired lateral sacs (completely separate chambers on either side of the head). Vocal sacs are outpocketings of the floor of the frog’s mouth. When calling, a frog closes its mouth and nostrils, and expels air from its lungs through the larynx and into the vocal sacs. The vibrations of the larynx emit a sound which resonates within the vocal sacs. The frog continues calling as muscles within its body wall force the air back and forth between the lungs and vocal sac. The thickness of the vocal sac wall in frogs varies. Typically, small frogs that call in the air (spring peeper) have thin vocal sac walls, whereas those that call in the water, particularly large species (green and bull frogs) often have thick-walled vocal sacs that appear swollen, not inflated like a balloon, when filled with air.


Killdeer Distracts Predator by Feigning Injury

4-15-13 killdeer IMG_8336

Killdeer arrived back in northern New England last month and have already begun nesting. Being a ground nester, the killdeer has many mammalian predators from which it needs to protect its eggs, including weasels, skunks, opossums and raccoons. Nesting killdeer have a number of responses to predators, which include several different types of distraction displays which draw attention to the bird away from its nest. One of the most common displays is to feign injury by assuming a position which makes the bird appear vulnerable. When a predator approaches, the bird runs away from the nest, crouches with its head low, wings drooping and tail fanned and dragging the ground to display its rufous rump-patch. The predator typically follows, seeing an easy meal, and as soon as it gets too close for the killdeer’s comfort, the killdeer continues to lead it off by alternate flights and sprints.


Red-osier Dogwood Stems

 

 

4-8-13 red-osier dogwood IMG_8874Red-osier dogwood (Cornus sericea), as its name implies, lends color to wetlands year-round, but it really comes into its own at this time of year.  In early spring this shrub is especially noticeable, as its red bark becomes much more vivid due to anthocyanin pigments which are affected by light intensity.  Although it can tolerate light shading, the stems and branches in shaded sites tend to be greener.  Native Americans utilized every part of this shrub,especially the stems and shoots.  Inner bark was used in tobacco mixtures during the sacred pipe ceremony, branches and shoots were made into baskets, dreamcatchers, bows and arrows, and peeled twigs were used as toothbrushes for their whitening effect on teeth.


Mourning Cloak Butterflies Emerging from Hibernation

4-11-13 mourning cloak IMG_2827

A male mourning cloak butterfly basks in the sun on an eastern hemlock while its dark wings act as solar collectors, warming the hemolymph (a circulatory fluid analogous to blood) in the wing veins and returning the warmed fluid to the butterfly’s body until it reaches a temperature sufficient for flight. This butterfly has just emerged from hibernating in a sheltered spot, such as behind loose bark. Because they overwinter as adults, mourning cloaks are one of the first butterflies to be seen in the spring.  The adults mate and lay eggs, and the caterpillars that hatch from the eggs will metamorphose into adults in June or July.  After feeding for a short time, the adults become dormant (estivate) until fall, when they re-emerge to feed and store energy for hibernation.


Migrating Dark-eyed Juncos Passing Through New England

4-10-13 dark-eyed junco2 IMG_9530This week those of us in the Northeast have been inundated with dark-eyed juncos, often referred to as “snow birds” due to their presence in much of the U.S. only during the winter months.  Although this member of the sparrow family breeds here and is found year-round in New England, over most of the eastern U.S. juncos appear as winter sets in and then retreat northward each spring.  Many of the juncos that we are seeing now are transitory migrants on their way to Canada and the Arctic to their breeding grounds.  They will remain there until next fall, when we will experience a similar influx.  Research has found that males migrate earlier than females, and that females tend to migrate further south than males. The timing of this migration is regulated primarily by the lengthening spring days.


Coltsfoot Blooming

4-9-13 coltsfoot IMG_7600You’ll find this early bloomer, Coltsfoot (Tussilago farfara), growing in some of the most barren spots on earth – roadsides that are awash with salt from the winter and that are nutrient poor, to say the least, but if sun and moisture are available, these dandelion look-alikes often thrive. Emerging this early in the spring, when temperatures can still dip down below freezing, has its challenges.  Hairy scales on the flower’s stem help keep the plant relatively warm.  Although the flower head is initially angled downward, when it blooms it straightens out and greets the sun.  During the night, and on cloudy or cold days, the flower closes, conserving heat.


Spring Peepers Emerging

4-8-13 spring peeper2 IMG_7463Sitting on top of the snow, still as a statue, a spring peeper gathers strength to make the long trek to open water, where, if it is a male, it will exercise its voice for the first time in many months. Like the gray treefrog and wood frog, spring peepers can freeze as solid as a rock for several months during hibernation and then, on a warm day, thaw out in a few hours and resume a normal, active life.  The formation of glucose and ice crystals that form outside of cells enable this phenomenon to occur.  Once hibernation has come to an end, peepers seek out wetlands, vernal pools and ponds to breed and lay eggs before they return to their home on the forest floor.


Common Raven Defends Nesting Territory

4-5-13 raven chasing red-tail2 IMG_8693Common ravens are known for their aerial acrobatics, often doing rolls and somersaults and other amazing tricks.  According to Cornell Lab of Ornithology, one bird was seen flying upside down for more than a half-mile. Young birds are fond of playing games with sticks, repeatedly dropping them and then diving to catch them in mid-air.  The pictured raven, however, was much too busy to be doing cartwheels in the sky.  It has a nest with eggs nearby, and during its morning patrol encountered a red-tailed hawk which it drove out of sight in a matter of seconds.  Although small mammals make up most of a red-tail’s diet, they are known to also prey on smaller birds, including defenseless nestlings, which the ravens will have in the next few weeks. (Because of the angle, the  24-inch-long, 53-inch-wingspread raven looks disproportionally larger than the 19-inch-long, 49-inch wingspread red-tail.)


Red-shouldered Hawks Building and Refurbishing Nests

4-5-13 red-shouldered hawk nest IMG_8573With winter temperatures still upon us, it can be challenging to find signs of spring in the hills of Vermont.  However, subtle signs do exist if you know where to look!  Notice the fresh greenery in this nest – it confirms that recent refurbishing has taken place by returning red-shouldered hawks.  Roughly two feet in diameter, a red-shouldered hawk’s stick nest is lined with moss, lichen, bark and conifer sprigs.  Other  items that have been used as building material for these raptors include ears of corn, corncobs, corn husks, tissue paper, nests of songbirds, straw, mullein, leaves, twine, various deciduous tree leaves, entire plants, dried tent caterpillar webs and plastic grocery bags. The pictured nest will serve as a nursery for two to five red-shouldered hawk chicks in about a month’s time, and as the nesting season progresses, sprays of conifers such as the hemlock sprigs you see here will continue to be added.


Wood Duck Courtship Displays

4-3-13 wood ducks  IMG_6045It’s been my life’s dream to witness the fledging of young wood ducks from their tree cavity nest in response to their mother’s calls below – perhaps this will be the year! Adult wood ducks have recently returned to northern New England, having already formed mating pairs. They now proceed to perform a number of courtship displays which enable them to maintain this pair bond. The most common display involves the male’s turning the back of his head towards the female as he swims in front of her while holding his wings and tail high. Chin-lifting, feather-shaking, wing-preening, neck-stretching and bill-jerking are just some of the displays that occur during wood duck courtship.


Silver Maple Flowering

4-2-13 silver maple IMG_8305Silver maple (Acer saccharinum) is second only to skunk cabbage when it comes to early spring flowering. Even with our nights still well below freezing, silver maple trees are bursting with blossoms. This close relative of red maple bears its male (pictured) and female flowers separately, sometimes on the same tree and sometimes not. Silver maple’s sap can be tapped and boiled into syrup, but the yield is much less, and it’s only about half as sweet as that of sugar maple.


Long-tailed Weasels Completing Their Spring Molt

email- long-tailed weasel in crotch of tree  IMG_7953Two species of weasels (smaller relatives of mink and otters) are found throughout New England – the long-tailed weasel (pictured) and the short-tailed weasel (also known as an ermine). Both are roughly the same size (somewhere between 9 and 16 inches), with long thin bodies and short legs. Visually telling these two species apart can be challenging unless you get a good look at both the tail and the body, and even then, it can be difficult. A short-tailed weasel’s tail is about 40% of the head and body length, whereas the long-tailed weasel’s tail is more than 45% of the head and body length. In the northeast, in November, both of these carnivores usually start shedding their brown summer coat for a white winter coat, and then molt and start growing in a brown coat again beginning in March. Further south, in Pennsylvania, less than half of the long-tailed weasels turn white, and none do south of the Pennsylvania/Maryland border. (Thanks to Tom Kennedy for photo op.)