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Taiga notes are ongoing updates about natural happenings in and around Denali National Park and Alaska's subarctic regions written by Denali Education Center Chief Naturalist Nan Eagleson.
September 8, 2009
The white spruce cone crop does not look terribly impressive this year but none-the-less, the red tree squirrel is actively cutting the unopened green cones from the upper branches of the trees. To extract and eat the seeds, they hold each cone in the forepaws and rotate it rapidly while chewing and cone scales flying in all directions. Because these squirrels don't hibernate, most cones are not eaten at this time of autumn but are cached at the bottom of a productive tree, in the squirrel's midden, a large pile of cones on the forest floor which are hidden away in underground connecting chambers, for their winter food. If the cones are small the squirrels often cuts an entire twigful of cones at a time. Studies have show that in Interior Alaska, red squirrels consume about 144 white spruce cones per day, and that a single midden may contain up to 16,000 cones. As much as 70 % of the white spruce cone crop may be harvested. The red squirrel's home-range is controlled by food supply and can be from ½ to 6 acres. It defends this territory against all other squirrels except during the mating season in March or April, reaching sexual maturity at about 1 year of age. With a marginal white spruce cone crop, their will be fewer red squirrels around this winter which will impact their predators the great horned owls and goshawks.
August 24, 2009
Summer is rapidly ending in the Denali area. In the past week the green leaves have become red and yellow and colder nights have ushered in all the changes that autumn brings. Moose calves which weighed only 20 pounds 3 months ago now weigh three hundred pounds. Their reddish brown coats have grown darker and the calves now resemble miniature adults. These calves are still nursing but at much reduced levels as they now feed much more heavily on leaves and twigs. Bull moose will soon shed the velvet from their antlers and by mid-September they will be engaged in the breeding season as the challenges of the rut begin. Moose claves will remain with their mothers during the breeding season although some older females with calves may avoid bulls and fail to mate for one or more years. Many bulls and cows will return to traditional rutting areas by mid-September and in some years, the peak of the rut in early October, may find Denali with low temperatures and deep snow. During severe winters dominant bulls may die due to serious injuries from the battles with other bulls for mating rights to cows. The surviving calves from summer will remain close to their mothers throughout the winter who will no longer be providing milk but will be providing important protection from predators such as gray wolves.
August 14, 2009
Northern flickers, the woodpeckers we see and hear most often in the Denali area use open forests and is the only woodpecker species which leaves for winter. These birds excavate large holes and usually choose large, decayed white spruce that still retains most of the bark. The bark keeps the interior wood moist, which speeds up heart rot which softens the interior of the tree. Often a good woodpecker tree will have more than one cavity in them. Sometimes these woodpeckers will use the same cavity for nesting and roosting several years in a row but often they do not. Their holes provide important sites for other birds that are unable to excavate cavities, such as boreal owls, chickadees and nuthatches which will nest and roost in the holes. In winter these holes are important cavities for birds which do not migrate to take shelter in during the long winter nights. Red squirrels and northern flying squirrels also may use the woodpecker holes for denning. What is known is that large, old trees are crucial to many birds and without decayed trees many cavity dependent bird species would not be able to find suitable nest and roost sites. During Denali's long cold winters, many permanent avian residents are dependent on these old, rotten trees with good cavities, carved by this summer visitor who adds to the overall health of the forest.
July 26, 2009
American golden-plover
By late July the days in Denali are getting shorter and some of our long-distance avian visitors have begun to migrate out of here. Shorebirds like American golden-plovers are some of the first to go. They will migrate both day and night and often double their weight before leaving, laying on fat to help fuel their long flights of thousands of miles without stops for several days. Spotted sandpipers are commonly seen along Interior rivers and lesser yellowlegs are frequently the most vocal nester near the many lakes, ponds and bogs of the park. Surfbirds, whose breeding range is confined to the high, bald mountains of Alaska, Yukon and Northwest Territories, are now heading to their wintering grounds which stretch along the Pacific coast from south-eastern Alaska to the Straits of Magellan. Long-tailed jaegers are on their way back to the South Pacific and Arctic terns, which undertake one of the longest migrations of any bird, will winter in Sub Antarctic and Antarctic waters of the Atlantic and Pacific. A tern banded in Alaska was recaptured ten years later in the same area, indicating a minimum of ten round trip flights. Upland Sandpipers, which nest in Denali on open grassy slopes and large dry river terraces covered with grasses, are on the way back to their wintering grounds on the pampas of southern South America. The growing understanding of how much shorebirds rely on critical areas in various countries shows the important role Alaska plays in these hemisphere-wide migrations. We now know that 100% of the North American populations of at least seven shorebird species come to Alaska as either migrants or breeders. Denali National Park is an important destination for some of these magnificent migratory birds and plays an important part in keeping these populations healthy.
July 15, 2009
The marten (Martes Americana), often called the pine marten is a member of the weasel family and they are just now beginning to enter their breeding season. Like other members of the weasel family (Mustelidae) marten hunt and kill small animals, most often voles, though they sometimes eat snowshoe hares, young birds and berries. During the berry season, they consume enough blueberries to turn their lips and scat blue! They live in many parts of Alaska although the greatest number of them live in mixed-wood forests of the Interior. Like squirrels, martens can reverse their hind feet and come down trees head first, the hind legs pivot at the hips. Like other members of the weasel family, the marten is able to delay part of its reproductive cycle. Marten mate in mid-summer when food is plentiful, but the fertilized eggs within females don't implant into the uterine wall until springtime, triggered by longer days. Marten kits are born in late March to mid-April and the young go their own way by August, beginning solitary lives that can last up to 14 years. The marten has also been called the American sable and its pelt can bring a high price for its beautiful dark fur, which is why they are known as Alaska trappers' bread and butter.
July 6, 2009
June was a month of warm sunny days and incredible wildflowers. Recently, temperatures have reached the eighties and the warm, dry weather has contributed to smokey skies and an abundant population of mosquitoes and other insects. The forest floor is dry and lichens look shriveled and colorless. However, lichens are hardy and fortunately, can tolerate drought and aversive weather conditions for extended periods of time. What they can't tolerate are airborne pollutants, which they absorb in toxic concentrations. Lichens form as a symbiotic relationship between algae and fungi. The algae have chlorophyll to photosynthesize sugars from sunlight, water and air. The fungus provides the protective structure and feeds off the sugars produced by the algae. Lichens are classified as part of the fungus kingdom which is neither plant nor animal but a third type of life that produces enzymes capable of breaking down dead organic matter, living tissue, and even rock. Lichens have the ability to live almost anywhere, on rocks, trees and other surfaces. The colors of lichens can vary greatly and the bright colors come from acid crystals stored in their tissues. This acid is what breaks down rock to form rudimentary soils and to etch holes in wood or other surfaces to give the lichens something to grab since they do not have roots. Most of the mosses found hanging from tree branches are actually lichens. True mosses are green like most other plants. It is thought that perhaps as much as 90% of all plants associate with fungus in the soil, and 80% of all plants could not survive without their fungal partners. The fungi extend the reach of the plant roots to obtain water and nutrients that otherwise might not be available. In return, the plants manufacture sugars to feed the fungi. Hopefully, we will soon get the rainy days of July (typically our wettest month), to nourish the flowers and forest floor and slow down the accelerated process warm temperatures bring with the added stress of dry, smokey air. And we'll then have the added benefit of our favorite edible fungi, the mushrooms.
May 27, 2009
The lovely, warm, sunny weather we have been enjoying in Interior Alaska for the past several weeks inevitably comes at a cost. Presently, there are several sizeable wildfires in Interior Alaska and a small one on the north boundary of Denali National Park. These fires are a reminder that our boreal forests are a dynamic place of change and these fires are the main agent of this change. It turns back the ecological clock by replacing older plants with younger ones. Sprouts rise from surviving roots. As a wildland fire burns, many places are missed and a patchwork of different habitats is created. This offers greater opportunity for a diversity of plants and animals. Over time, as regrowth proceeds, a succession of different plants and animals will make their homes in the burn area. As time passes, the plant community changes from herbs and grasses to willows and shrubs, then finally the climax trees such as white spruce dominate. Animal diversity changes along with the plant succession until fire once again burns the forest. Soon after a fire black-backed woodpeckers move into the burned forest and take advantage of beetle grubs that inhabit the burned trees. Within a few years voles, snowshoe hares, ruffed grouse and moose benefit from the willows and shrubs that are rejuvenated. Later, black bears will move into the newly forested areas along with goshawks and red squirrels. By around 120 years + the climax forest will primarily be white spruce as it begins to overtake the deciduous mix of aspen and balsam poplar. Eventually, the spruce trees age and accumulate years of dead needles and branches and the forest becomes loaded with fire starter. Last evening's sunset had that unmistakable hint of orange that mellows the views of distant hills and reminds us that great weather in Alaska always comes with a price.
May 8, 2009
The ice went out on the Nenana River, along the eastern boundary of Denali National Park and Preserve, this past week (sometime during the night of May 3rd) . Ice blocks are stacked up along the river's edge and will melt rapidly because of the warm weather we have enjoyed for the past two weeks. In early spring, Arctic grayling begin to congregate at the mouths of clear water streams and rivers just before breakup. In April and May, as soon as streams open, the fish migrate up as far as 100 miles from their wintering waters, which are usually deep holes in bigger rivers. Spawning takes place from mid-May to mid-June. Males establish spawning territories and will follow a female and court her with a display of the dorsal fin. The female will release eggs (4,700 or more per female) which the male covers with milt over a sandy gravel bottom. The eggs are adhesive and stick to the substrate and other bottom structures. After spawning, the adults move to their permanent summer residence and the young, which have been described as resembling "two eyeballs on a thread" begin feeding the third or fourth day after hatching, depending on the temperature of the water. Soon, when the mosquito population really emerges, insects will constitute nearly 65% of the grayling's diet. So, not only are Arctic grayling an important sport fish of Alaska, they also do their part for biological control of the abundant mosquito population.
May 1, 2009
The warm spring days of the past week have the snow disappearing fast and the Nenana River nearing breakup. Robins and juncos have arrived and golden eagles, ravens, gray jays and gyrfalcons are all on their nests. The few flocks of geese and trumpeter swans appearing overhead will likely continue on till finding open water on larger lakes and ponds but puddle ducks are putting down on the bits of open water that are now available. Mew gulls are here and the occasional red-tailed hawk and rough-legged hawk are circling through. The word is out that bears have emerged from their dens so, it is time to clean up our yards, bird feeders and any attractant which might peak their hungry curiosity. Willow catkins are opening everywhere and on south facing, dry slopes the first pasque flowers of the season are beginning to bloom. Now is the time to collect balsam poplar buds to make Balm of Gilead. The buds are easiest to collect when temperatures are cool, when warm, the buds are exceedingly sticky and many of the valuable resins are lost. These buds can be used in soothing, aromatic salves such as Balm of Gilead. Gather 1 cup of balsam poplar buds and simmer with 1&1/2 cups of lard or moose fat (like the native people historically used), for an hour then strain through muslin cloth. If the preference is to use olive oil or almond oil, the salve can be thickened with beeswax. The fragrance is lovely and the salve is used for assorted skin irritations because of its antioxidant properties. May is the month when bird migration peaks, marmots, wolves, lynx, and hares are born and caribou and moose begin calving. What a glorious time of year!
April 10, 2009
Now that sun exposure has increased dramatically, willow catkins are beginning to appear on some species of willows in the Denali area. The willow family includes a large number of species that are an important source of food for herbivores such as moose, snowshoe hare, ptarmigan and beaver. The sweet nectar of the early flowering willows provide most of the needed energy for the bumblebees that are active before the snow has even melted and ptarmigan and grouse feed on the willow buds throughout the winter. Willows are unisexual with each individual plant bearing either male or female flowers which are crowded into catkins. Willow species can be difficult to identify because of possible hybridizing. Most willow species vary according to their growing conditions and in some cases distinct species within a thicket resemble each other more than specimens of their own species growing under different conditions. Identifying factors such as leaf shape, size, color, etc. can vary greatly whereas catkin and pistil characteristics remain fairly constant. Willows have always been used in a multitude of ways by humans because they are so well adapted to the disturbed areas humans inevitably create. One of their primary uses in Alaska is for reclamation of disturbed sites and stabilization of riverbanks. Salicin, the chemical that preceded acetylsalicylic acid (aspirin) was first isolated from willow. Many people are familiar with diamond willows which are carved into beautiful walking sticks or furniture. The "diamond" is caused by heartwood scarring following an infection by a fungus called Valsa sordida. Lots of wickerworks such as baskets, snowshoes, fish traps and other important items have been made from willows for centuries. Today, particularly for Alaskan bush communities where fossil fuels are exorbitantly expensive, there is a developing interest in willows as a source of renewable energy. This will be an interesting development to follow as alternatives to fossil fuels seem to be growing all around us.
March 30, 2009
The month of March in Denali is a favorite of local residents for getting out into the surrounding country and traveling while snow and ice conditions still allow access to skiers, mushers and snowmachiners. Having passed the Vernal Equinox over a week ago, the lengthening days bring genuine warmth as the sun moves closer to our zeneith. Snow buntings will arrive any day now while boreal owls, northern hawk owls, great gray owls and great horned owls are all doing their territorial hooting and calling. The first sighting of returning golden eagles have been made and ravens, magpies and gray jays are all busy nesting. Lynx mate and porcupine babies are born in March. As the month comes to an end our year-round resident owls will be nesting. These owls were in loose pairs throughout the winter but with the lengthening days their behavior slowly changes. The photoperiod is the environmental trigger which initiates the hormonal changes needed to stimulate closer pair formation. Receptors in the hypothalamus, deep within the brain, sense the changes in day length and trigger chemical messengers to release hormones that awaken the ovaries and testes which leads to the release of crucial sex hormones. The owl pairs start to roost together, vocalize frequently, preen and nibble the sensitive feathers on each other's face and reinforce their bond in the first steps towards successful reproduction. These pairs may not breed every year, depending predominantly on food availability. The age which most owls do begin to pair and raise young is relative to the life span of the species. Larger owls generally live longer and typically take longer to reach sexual maturity. Great horned owls don't begin to breed until they are at least two years old or older, while smaller owls like the boreal owl start to breed when they are one year old. In these northern latitudes, day length, or photoperiod, is the environmental trigger used by most wildlife to synchronize seasonal behaviors. With these lengthening days of spring, there is a lot going on, all around us. No small wonder, after a long winter, it is a favorite time of year.
February 23, 2009
On these sunny, late February days, our Denali skies are showing the first signs of spring with wonderful courtship flights by ravens. Paired ravens are vocalizing and passively defending nesting territories as they engage in areal acrobatics. The Common Raven (Corvus corax) is mainly found in mountainous areas and can survive at all seasons in diverse habitats ranging from hot deserts to the high Arctic. The raven is the largest species of song birds and although their voice is not very musical it is incredibly varied, from deep baritone croaks to high bell like notes. They produce more than 30 vocalizations which they sometimes utter in quick succession. The juvenile calls are loud and squaking. The raven is the largest all black bird in the world but many folks confuse crows and ravens. Ravens are much bigger, have a long head and large heavy bill and a wedge shaped tail. Ravens often soar while crows never do. We dont have crows here in Denali but the Northwestern crow (Corvus caurinus) can be found south of the Alaska Range along the coast of Alaska. Ravens first breed at 3 or 4 years and mate for life. They remain paired all year and by mid-March adult pairs are roosting near their nesting location. Both sexes help build a bulky stick nest on a cliff ledge or atop large conifer trees. They may use the same site year after year, adding material on top of old nests. Ravens are magnificent fliers and seem to exhibit an aloof attitude to humans, never coming to feeders and, as Alaskan writer Sherry Simpson suggests "picking at the carcass of civilization."
February 9, 2009
The only caribou in the Denali area now that are sporting antlers are the females. Like other members of the deer family, caribou grow and shed their antlers each year. However, caribou are the only species in which both sexes grow antlers. By now, the bulls have shed their antlers but in March, velvet knobs will appear. By November or December the older bulls begin to drop their antlers and by February most of the younger animals have dropped theirs as well. The female's antlers develop from June to September, but they will not drop them until the birthing time in spring. The cow's antlers are more slender and much shorter. Caribou are cloven-hoofed mammals. Their large concave hooves splay to carry them across the snow and tundra and to shovel down through snow to reach lichen, a vital winter food. In summer, the foot pads are large and the edges of the hooves wear flat so that the pad rests on the ground. In winter, the hooves grow in length, the pads shrink and become tough, and the hair between the toes form tufts to cover the pads, protecting the foot from heat loss. These animals also have other efficient ways of adapting to the cold. In winter, most of the caribou retreat to the forest for shelter. Their pelage is of two types: long, stiff, hollow guard hairs that trap warm air next to the skin and a wooly underfur. One of the highlights of this long season in this area is the presence of caribou, enduring the wildly vascillating weather of Denali winters.
January 27, 2009
While arctic ground squirrels and hoary marmots are safely in their burrows, hibernating for the winter, collared pika (Ochotona collaris) remain active, feeding on the dried hay they stored the previous summer and fall in their burrows. The pika cures the plants before stacking it in the haypile and they need to store at least 12 pounds of vegetation to make it through the winter, with some overachiever pika storing up to 50 pounds! Pika are sometimes appropriately called "rock rabbits" because their closest relatives are hares and rabbits. All of these are members of the mammal order Lagomorpha and they all share a similar digestive feature in that they are coprophages. Pikas and snowshoe hares reingest their pellets to get full advantage of the available nutrients. Hares and pikas have a very enlarged cecum in which bacteria ferment plant material, extract the energy and convert it to volatile fatty acids, proteins and vitamins. Collared pika are closely related to Ochotona princeps the pikas in the Rocky Mountains and southern British Columbia. The two populations likely differentiated during a glacial episode in the late Pleistocene in which the northern populations of Alaska, Yukon Territory and northern British Columbia were isolated from the more southerly populations by continental glaciers. Even today there is still a separation in the geographic populations by over 500 miles in central British Columbia. Pikas select a different assortment of plants when haying as opposed to simply grazing. When haying, pikas are primarily selecting non-woody, non-grass, herbaceous plants, (forbs). Dwarf fireweed, horsetails, low-bush cranberry leaves and berries, willow leaves and Labrador tea are just a few of the food species found in their hay piles here in Denali. Unlike the cyclic populations of snowshoe hares, the populations of pikas remain relatively stable. However, in more southerly latitudes pika habitat is being marginalized by climate change and they are literally running out of alpine habitat as tree lines and shrub lines move up in altitude and latitude. Sightings of active pika have been made on talus slopes in the Denali area when temperatures were well below freezing, confiming these amazing little mammals are well adapted to this subarctic climate.
January 14, 2009
The temperatures in some areas of Interior Alaska are as much as 90 degrees F warmer today than they were a mere week ago, and it is raining! These extremely varying temperatures probably don't interfere much with what is happening right now in the hibernating dens of Ursus Arctos, the grizzly bears. Typically, the cubs are born in January in the den and are altricial (dependent) being blind, weighing only about a pound and covered with fine gray hair. In Denali, the average number of cubs is 2 but litters can vary from one to three. Because the female is in torpor while in the den, the cubs will need to find a nipple and nurse until they emerge from the den in late April or May with the mother. The mother bear has three pairs of teats: two pairs pectorally on the chest and one pair inguinally between the hind legs and the cubs will nurse from all 6 different teats. Bears are unusual "hibernators" because of their large size. They don't fall into a deep torpor and decreased consciousness like most true hibernators. Bears must be able to become alert because of giving birth and retaining the babies in their dens for 4 to 5 months. They sleep but are not out cold. Bears are also unique because they have adapted to recycle their waste products. A fecal plug forms and prevents waste from accumulating in the den. Given the weather so far in '09, bears seem pretty clever to opt out of trying to make a living in winter and just sleep through it!
January 5, 2009
The extremely cold temperatures we have had in Interior Alaska for the past week confirms the hardiness of the year-round residents, especially those of the avian family. Most song birds need to keep their internal body temperature revved up to about 110 F. Given the ambient air temperature in the Denali area has recently vacillated between -30F to -52F in some places, it is a marvel that these loyal chickadees, redpolls, crossbills and grosbeaks show up at the feeders at first light, daily. Black-capped chickadees survive extremely cold nights by roosting in tree cavities to reduce heat loss and sleeping in a hypothermic state to conserve energy. Common redpolls eat as much as 42 % of their body weight in seeds during a single day and white-winged crossbills must eat about one spruce cone seed every seven seconds during the brief daylight hours in order to survive these cold periods. The upper and lower bills cross at the tip and allow the crossbills to twist the stalks of the spruce cones, then bite between the scales to expose the seeds. The cones of different tree species vary in size from different regions and crossbills have bills that are sized for opening the predominant cones they encounter in the regions they occupy. In contrast with the specialized crossbills, the Common raven survives the winter by eating whatever it can find such as carrion and garbage, and occasionally will hunt cooperatively in groups. It is amazing to watch ravens in the frigid air doing aerial acrobatics and spectacular dives all for the sake of fun. Great Horned and Boreal owls thaw frozen prey by incubating them as they would eggs. Birds increase their visits to feeders in harsh weather, and small species, which are more constrained energetically, benefit greatly from feeding. So, keep those feeders full, this cold spell is expected to continue for at least another week!
December 24, 2008
It is now 3 days past winter solstice and we have gained one minute of day light in the Denali area, near latitude 64 degrees north. Christmas Day, tomorrow will be one minute and 3 seconds longer than today. So, the sun is incrementally moving north since its farthest southern journey on December 21st. Each year the time of a solstice (or an equinox) comes about five hours and forty-nine minutes later than the one the year before, except on leap years, when it comes about eighteen hours and twelve minutes earlier. The primary reason for this quirky annual pattern is the use of a leap year to partially correct for the year actually being about 365 ¼ of days long. Sun rise today was at 10:50 AM and Sunset at 3:15 PM. Sunrise and sunset refers to the times when the upper edge of the disk of the Sun is on the horizon, a hard thing to see here in the Alaska Range unless you are standing on the top of a high peak. What we really see here is twilight. Before sunrise and again after sunset there are intervals of time, twilight, during which there is natural light provided by the upper atmosphere, which does receive direct sunlight and reflects part of it toward the Earth's surface. There are three kinds of twilight, civil twilight, nautical twilight, and astronomical twilight. Civil twilight begins before sunrise and ends after sunset when the center of the Sun is 6 degrees below the horizon. Nautical twilight is defined when the sun is 12 degrees below the horizon and Astronomical twilight is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the Sun does not contribute to sky illumination. These technical definitions don't really compute when we are enjoying any amount of natural light during this time of year, there is truly something magical in the twilight hours of this time of year. Happy Holidays!
December 18, 2008
The Denali Park Christmas Bird Count (CBC) is taking place on December 27th and Cantwell, AK will be doing a CBC for the first time this year on December 28th. The CBC happens one day, between December 14 and January 5. It begins at midnight on a designated day and ends the following midnight. Participants work in teams to count as many bird species and individuals as possible in assigned sections of a count circle fifteen miles in diameter. Feeder counts are also tabulated. Groups gather to compile their counts, and the tallies are combined with counts from across the United States, Canada, Latin America, and the Caribbean. The CBC was founded in 1900 by ornithologist Frank Chapman as an alternative to the Christmas "Side Hunt," a competition to see which team could shoot the most birds and other animals. With more than one hundred years of data, the Christmas Bird Count has become a valuable source of information about changes in bird populations over time. Data from the CBC have helped track irruptions of boreal seed-eating birds such as pine grosbeaks and white-winged crossbills. More recently, the counts have been used to document declines of American crows that appear to be related to West Nile virus. The long-term records have also shown how the ranges of birds have expanded or contracted through time, such as the northward spread of black-billed magpies here in Interior AK. The counts also track changes in numbers, such as declines of Bewicks's wrens in the eastern United States since the 1930s. As the longest-running data set on bird populations, the Christmas Bird Count helps scientists keep track of long-term changes. The CBC is organized through local coordinators. Call Nan Eagleson at (907) 683-2822 for the Denali Park CBC and Jill Boelsma at (907) 768-2266 for the Cantwell CBC. A five-dollar donation is requested from participants. Audubon is the sponsoring organization.
This fall, many people around Denali are seeing more black-capped chickadees in the area and at their feeders. Black-capped chickadees survive extremely cold nights by roosting in tree cavities, reducing radiant heat loss by 60 to 100% compared with roosting in open air. They can also lower their body temperature overnight by as much as twenty-one degrees, sleeping in a state of hypothermia that conserves energy. During the short days of winter here in Alaska, chickadees must eat enough food during the brief 4 hours of daylight so they can fast for the next 20 hours in the cold darkness. It will be interesting to see if this year's CBC shows an increase in actual numbers of black-capps compared to previous years. This will be the 17th year that Denali Park has participated in the count and the 109th annual Christmas Bird Count.
December 5, 2008
In the Denali area and certain other parts of Alaska, there is a healthy population of beaver (Castor Canadensis) and by now they are holed up in their winter lodges . They do not hibernate but will stay in the dark chamber of mud and sticks with their life long mates and offspring from several previous years. Their combined body heat helps to warm their home even during the severest temperatures. The beaver eats roots, tubers and the inner bark of trees and as a consequence, its own meat is sweet and tender. To avoid becoming everyone's favorite prey, this vegetarian took to the water a long time ago and is well adapted to the aquatic life. Its dense coat conserves heat and its multipurpose scaly tail functions as a rudder, as a place to store fat for lean times, as an internal temperature regulator and as an early warning system to other beavers when it slaps it against the water. Beaver have a pair of glands in the anal area of both sexes which secrete castoreum, the musky oil the beaver uses to grease its coat and mark scent mounds to delineate its territory. Castoreum was used in the Middle Ages as medicine to cure everything from headaches to impotence. It is high in salicylic acid; the basic ingredient of asprin, which the beaver ingests by eating on willow bark. To extract the most calories from its high-fiber diet, the beaver eats everything twice when food supplies are low, a practice called coecotrophy. Snowshoe hare do this as well and ruminants such as moose manage this by burping up their ingested food and chewing the cud. Double digested beaver stool looks like sawdust, not unlike the contents of winter moose "nuggets" when torn apart. Beaver also have a number of additional features which equips them for underwater. They have valves which close off their nose and ears; membranes over their eyes which serve as goggles and skin flaps behind their front teeth to allow them to tow tree branches in their teeth without swallowing a load of water. The beaver's ratio of brain size to body weight is the lowest found among mammals but, none-the-less, they are amazing engineers. Interestingly, it appears that much of their building techniques appear to be learned during their long childhood. The European beaver (Castor fiber) is nearly identical in appearance to the American beaver, but it does not build dams. History suggests that the intricacies of dam construction were lost to Castor fiber during the centuries when only a few survived in parks because their numbers were decimated for the local fur trade. The Europeans then turned to North America for beaver, after wiping out their own, and around 300 years later, about the time the first wagon train made its way West on the Oregon Trail in 1843, the beaver had almost entirely been trapped out "back East". Beaver are nature's natural hydrologists and after three hundred years of incessant trapping the North American fur trade altered the physical landscape of the American West, which is now, consequently, far more arid.
November 24, 2008
This is an important time of year for Dall sheep in the Denali area. The most active mating season for Dall sheep goes from mid November through December after increasing snow has forced the sheep to descend from their summer range. These wild white mountain sheep are found only in central and northern Alaska, the Yukon Territory, and northern British Columbia where mountain ranges provide favorable habitat because the snowfall is relatively light and strong winds keep the exposed ridges free of snow. As mating activity lessens, in late December and January, the rams drift away from the ewes and form bachelor groups. The winter is spent on relatively small ranges of south-facing, exposed grassland, where the sheep paw through shallow snow to find food. Lambs are born between early May and mid-June and weigh 5 to 6 pounds at birth. Normally one lamb is born per ewe, although twins occur occasionally. When hare numbers have crashed lynx may go after Dall sheep, along with wolverine and grizzly bears on occasion but their effect on population numbers is unimportant according to most biologists. Probably the most serious threat to wild sheep numbers is lack of good quality winter food.
November 14, 2008
The Nenana River, the eastern boundary of Denali National Park, is beginning to freeze along its edges and in some places from the bottom up. The banks along its edge show a variety of tracks of hooves and feet of the local wildlife but one of the more distinct signs of a playful resident is the slide of an otter down the snowy bank into the water. Near the campus of the Denali Education Center is a spot where several of these slides show the otters seek company when they turn to sport. River otters, Lutra Canadensis, tuck their forelegs straight beneath them and go sliding belly whopper style into the water. The river otter is perhaps the most playful four-footed animal in North America. In the summer they will use a grassy bank as a substitute slide for snow. The dense fur of this long-bodied, short-legged animal is brownish when wet, and grayish when dry, and with webbed feet, they have torpedo like speed in water. Litters of young pups are usually two or three and are born in February to April. The mother teaches the pups to swim and the father helps to train them. As the summer wanes, the father goes his own way but the mother and pups will remain together as winter approaches. The otters will circle a wide area for the necessity of following a food supply. In winter, as streams and lakes freeze over, the otters must move on till they find open water. The otter is a carnivore and eats what it can catch for fish as its main prey. In autumn, Arctic grayling move back into the Nenana River when the water clears, as its glacial source no longer contributes a load of sediment. The fish will over-winter in deeper holes in a sort of torpor and be a fairly easy catch for the otters.
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October 20, 2008
As our population of winter resident birds develops, the white spruce cone crop promises a nice compliment of seed eaters this winter, especially the finches such as pine grosbeaks and white-winged crossbills. All of our local ponds and smaller lakes are now frozen and ice is floating down the Nenana River. Birds seen at feeders in the Denali area this past week were varied thrush, juncos, red-breasted nut hatches, boreal and black-capped chickadees, white-winged crossbills, magpies and several other residents. Likely, the varied thrush has moved on by now but it will be interesting to see who remains over winter. Some birds are expanding their winter ranges and Denali is a good place to note these changes. The 109th Audubon Christmas Bird Count, which takes place during a 24 hour period between December 14th to the 3rd of January, will be a snapshot of local birds. This year there is a new CBC in the Denali area with the addition of the Cantwell Christmas Bird Count. The Denali Park CBC will be in its 17th year of participation and the two counts combined should give us a good indication of who our feathered neighbors are. Now that it seems our snow is here to stay and our temperatures are well below freezing we should take note of our hardy avian residents. Crossbills are finches that live in the boreal forests and feed on the seeds of conifer trees. They have specialized bills with thin, overlapping tips to pry open the cone scales allowing access to the seeds within. In years when white spruce cones and seeds are plentiful, white-winged crossbills have been known to successfully nest and raise young for every month of the year in Alaska, excluding January.
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October 9, 2008
The recent snowfalls on the north side of the Alaska Range in Denali Park are earlier than usual and it seems likely it will stay till spring. The accumulation on the higher slopes over the past week is enough to drive some grizzly bears (Ursus arctos) into the den or down to lower elevations in search of food. The denning period for most Denali grizzlies typically extends from late October and early November to April or early May but early snows lead to earlier denning, particularly for pregnant females and females with cubs. The berry season, which began late, was cut short by early snow. Denning is correlated with food scarcity. When autumn snows begin to accumulate significantly and the ground freezes; berries are buried by snow and bears can no longer dig for roots and excavate ground squirrels. Sometimes a den may be dug long before the time of use, or not until time of retirement. Most dens are lined with dry grass and herbaceous material and because grizzlies can so easily dig in loamy or gravelly soil they typically dig new dens rather than search for one used previously. Bears will den throughout their range and don't necessarily move to lower country to retire for the season. During winter, bears do not truly hibernate but experience a period of dormancy when their body temperature drops and the metabolic rate is reduced. Occasionally, bears will emerge from their dens in winter, particularly during spells of warm weather and during years when food is scarce prior to denning. Duration of dormancy is longer in areas having severe climates and females with new born cubs emerge later than single bears. It is thought that there are approximately 300-350 grizzly bears on the north side of the Alaska Range. Given the early snow and the short berry season, perhaps we'll see a few of them wandering around in the Park this winter.
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September 30, |
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