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Showing posts from December, 2010

An Early April

After a cold and snowy start to winter, April has made an early appearance in the American Midwest. Strong southerly winds, ahead of the next winter storm, have pumped mild, humid air into the Heartland, priming the region for thunderstorms, which rumbled through Missouri overnight and into this morning.

This brief spring interlude, sporting afternoon highs near 60F and morning lows near 50F, is already beginning to fade; blue skies to the northwest, so inviting from a distance, warn of cold air behind the front. As the storm moves off to the east, northerly winds will push this air into Central Missouri and winter will reclaim the State.

These weather oscillations usually settle down in January as the jet stream assumes a steady, more southern track, keeping us on the cold side of that atmospheric boundary. But the word "usually" is a relative term and North American weather patterns are notoriously fickle. We have reason to hope that April makes several more visits bef…

Winter & the Elderly

In nature, winter is the culling season. Wild creatures that are old, sick, injured or malnourished often succumb to the harsh conditions; hypothermia, starvation and predation all take a toll. Early man also faced these threats as he emigrated from his tropical home to northern latitudes.

Most older humans will admit that their tolerance to cold weather has decreased with their advancing age and there are physiologic reasons for this perception. As we age our metabolic rate falls, our activity decreases, our calorie intake is reduced and our body fat begins to diminish; all of these factors make it more difficult to retain and generate heat. Furthermore, older persons often have chronic conditions that lead to impaired mobility and balance, making them more prone to falls and injury; the presence of snow and ice only exacerbates this risk. Finally, all of us are more likely to be infected with viruses during the colder months as our indoor lifestyle increases contact with other …

Unnoticed Visitors

Novice birders, focusing on common, local, avian residents, often overlook migrants and seasonal visitors that resemble those birds. One such visitor is the purple finch, a fairly common winter resident in California and across the eastern half of the U.S. Since they are similar in appearance to the abundant house finches, their presence may not be appreciated.

A bit larger, stockier and possessing a heavier bill, purple finches are also recognized by distinct plumage characteristics and a notched tail. The males have a rasberry wash over their head, breast and rump, which mixes with brown on their back and is diffused with white on their chest and abdomen; in contrast, the male house finch has an uneven, orange-red coloration, primarily on the head and upper chest. Female purple finches, like female house finches, are streaked with white and brown but have a prominant white facial stripe, just above each eye.

The summer breeding range of purple finches extends across the coniferou…

Unaweep Canyon Mystery

While the field of plate tectonics has solved many geologic mysteries, others remain. One of these is Unaweep Canyon in the northern portion of the Uncompahgre Plateau, in western Colorado; unlike other canyons, it has two mouths and a divide along its course, which is now traversed by Colorado Route 141.

Geologists have long debated the natural history of Unaweep Canyon. Some have suggested that, since the canyon is U-shaped, it was carved by mountain glaciers during the Pleistocene; however, closer examination of its floor has revealed that it is a V-shaped, stream-cut canyon, since filled with erosional debris to produce the flattened bed. Others, realizing that the small streams that now flow east and west from the divide could have not produced this magnificent canyon, with its massive walls of hard, Precambrian rock, theorized that the Colorado River originally sculpted Unaweep before changing course to skirt the northern edge of the Plateau.

The most recent evidence suggests…

The Davis Mountains

Looking at a satellite map of the U.S., one notices a dark smudge in West Texas, north of the Big Bend area and just south of I-10. This dark terrain reflects the vegetation and rock formations of the Davis Mountains, which stand out against the pale, drier landscape of the Chihuahuan Desert.

Volcanic in origin, the Davis Mountains are remnants of two large calderas and their associated rhyolite lava flows, ash tuffs, cinder cones and laccolith formations. Persisting for 10 million years, the volcanic activity began in the Oligocene, some 35 million years ago, when grasslands were evolving across the Great Plains and mammalian megafauna dominated the scene. The Davis Mountains cover much of Jeff Davis County and represent the most extensive mountainous region in Texas; summits range from 3500 to almost 8400 feet. Like the Chisos Mountains of Big Bend National Park, the Davis Mountains are part of the Trans-Pecos Volcanic Field, which extends across West Texas and into Northern Mex…

Red-Shouldered Hawks

Though less conspicuous and somewhat smaller than their red-tailed cousins, red-shouldered hawks are fairly common throughout the eastern half of the U.S. and along the coast of California. Identification of this buteo is generally made by the fine, rust-colored barring on its chest, its relatively long, banded tail and its loud, high-pitched, descending call; the red shoulder patches, for which it is named, are not always apparent.

Preferring wooded swamps and riparian forest, red-shouldered hawks usually hunt from a low perch and feed on a wide range of prey, from mice and voles to lizards, frogs, snakes and songbirds. Often considered to be the diurnal counterpart of barred owls, both raptors share the same habitat and both have been threatened by the gradual destruction of forest and wetlands. Ironically, red-shouldered hawks, though often heckled by jays and crows themselves, are known to join these birds when they mob great-horned owls, red-tails and other large raptors.

Like…

White Christmas

Caught between high pressure over the Northern Plains and low pressure over the Texas Panhandle, we are getting our Christmas snow here in Missouri. The low is sweeping Gulf moisture in from the south while flow around the high is bringing colder air down from the north; the latter will hang around for several days, assuring us of a White Christmas.

The snow began overnight and has already dropped a few inches of wet snow on the frozen ground; by tomorrow morning, we may have half a foot or more and it will look very much like the Christmas Day that most Americans hope to experience. Snug in our heated homes, we can look out on the winter scene with no sense of alarm and, of course, children will enjoy romping through or sledding over nature's blanket.

Though challenged by the snow cover, wildlife are well equipped to survive its presence; the feeder sites will be especially busy but our winter birds would manage just fine without the handouts. Some mammals will den up until co…

The Pineapple Express

Produced by an atmospheric trough over the eastern Pacific, the Pineapple Express is a plume of deep, tropical moisture that is swept into the western edge of North America. Developing ahead the the trough's leading cold front and reinforced by circulation around high pressure to the southeast, this flow of warm, humid air, which originates near Hawaii, is forced to rise as it invades the Continent, producing heavy valley rains and dropping copious snow across higher terrain.

In most cases, the plume first strikes the Pacific Northwest; as the trough advances eastward and the angle of its cold front changes, the stream of moisture moves southward, through California and into Mexico. Should the front become stationary, as it did earlier this week, the onshore flow of tropical moisture may continue for several days, producing floods, mud slides, avalanches and great skiing conditions from the Coastal Ranges to the Rockies.

Once the trough moves across the western edge of North Ame…

Merry Consumption!

It's the most wonderful time of the year....especially for retailers. Pressured by tradition and expectations, Christians of all kind, from timid secular participants to evangelical zealots, invade the malls, spending lavishly to shower one another with the latest outfits and gadgets. Though bought with loved ones in mind, the gifts also soothe the mind of the purchaser, who must fight the guilt that pervades this season.

While born of a simple story about a charismatic figure who, by all accounts, led a spartan life, Christmas has become a three-month event, focused on extravagant consumption. Some might argue that this annual frenzy, instigated by Big Business and promoted by its army of advertisers, is crucial to the global economy but, in the end, those of us in "developed" countries receive far more than we truly need.

Excess consumption, combined with unbridled population growth, is perhaps the greatest threat to natural ecosystems across our planet. The acquis…

A Morning of Raptors

Venus gleamed brightly in the eastern sky as I drove to our meeting site for the annual Christmas Bird Count. Our group, as usual, was assigned an area south of Columbia that extends from wooded uplands down to the banks of the Missouri; most of this territory is covered by rolling terrain with forested hills, rocky creek channels and valley farms.

The theme for this year's count was set when we heard and spotted two barred owls just before dawn. Clear skies and a minimal wind provided a perfect, if chilly, morning for birding and a large number of species were logged; but this was a morning for raptors. Not long after finding the barred owls, we encountered six bald eagles (5 adults and 1 immature) along the Missouri River, which was nearly covered with floating chunks of ice. As usual, red-tailed hawks were common above and along the farms fields and, today, were matched in number by red-shouldered hawks, which perched in wooded meadows. A sharp-shinned hawk streaked across…

The Scent of Skunk

In winter, cold, dry air and frozen ground suppress most of nature's fragrance. One potent exception is the scent of skunk musk, which wafts through the air and is detectable by our relatively poor olfactory system for up to a mile from its source.

Skunks, members of the Mephitidae Family, are represented by at least ten species across the globe, most of which are native to the Americas. Omniverous and crepuscular, skunks roam about to feast on a wide variety of plants, small animals, eggs, garbage and carrion; guided by an excellent sense of smell but hampered by poor eyesight, they represent a large portion of our roadkill. Of course, it is their volatile and irritating musk that wards off many natural predators (great horned owls excluded); produced in perianal glands and found to contain a mix of sulfur-containing thiols, this noxious musk can be accurately ejected for up to 15 feet. Mustelids (weasels, otters, martens, badgers and wolverines) have similar musk glands but,…

Great Gray Owls

One of the least conspicuous birds in North America, the great gray owl inhabits the boreal forests of Alaska and Canada and the mountain forests of the Cascades, Northern Sierra Nevada and Northern Rockies; during the winter months, they may also be encountered in Minnesota and northern New England. Preferring dense, coniferous woodlands, they hunt primarily at night but become increasingly crepuscular or diurnal during the colder months of the year; it is then that they are most often observed, perched on a limb that overlooks a forest clearing. While this owl is seldom seen, its deep, resonant hoots often echo through remote northern forests.

Though great grays are our largest owls by length and wingspan (the latter may be up to 5 feet), they are not as heavy as great horned owls; their large head and prominant, ringed facial disc accentuate their size and make their yellow eyes appear to be small and closely spaced. Despite their size, great grays are not overly aggressive and …

Winter Farmlands

Yesterday afternoon, the farmlands east of Columbia presented a bleak winter landscape; snow covered the ground, dead corn stubble and dry, yellow grass quivered in a cold, east wind, dark, barren woodlands shrouded the stream channels and a flat, gray sky diffused and scattered the weak winter sunlight. Were it not for the occasional grove of eastern cedars, one could have painted the scene in black and white.

Amidst this harsh and forbidding environment, one might not expect to see much wildlife but they would be wrong. As expected, raptors dominated the scene; red-tailed hawks surveyed the grasslands from the barren trees, northern harriers skimmed above the cropfields and American kestrels hunted from the powerlines. Skeins of Canada geese moved across the sky, eastern meadowlarks streamed across the roadways and large flocks of blackbirds settled in the fields. Dark-eyed juncos and white-crowned sparrows combed the roadside thickets, eastern bluebirds and mourning doves perch…

Mourning Dove Sit-In

Faced with snow-covered ground and an invasion of Arctic air, mourning doves have gathered in our large magnolia over the past two days; since this tree is on the south side of our house, it is protected from the cold north wind and receives plenty of sun, even in the winter.

Like many bird species, mourning doves form large, sociable flocks during the colder months but, unlike the others, these mellow birds assemble with little fanfare. Were it not for their distinctive forms, huddled in groups on the bare branches, one could easily overlook them. Content to watch their high strung neighbors as they squabble over the nearby feeder, the doves sit patiently, basking in the sun and waiting to partake of seed that falls to the ground. If not spooked by a sharp-shinned hawk, they may sit there all afternoon, heads on chests, oblivious to the winter chill.

Their peaceful sit-ins are a welcome sight during this trying season; the tranquility is infectious and their calm, polite demeanor …

Night of the Geminids

While not as famous as the Perseids of August or the Leonids of November, the Geminid meteors of December offer the most reliable display of the year. Produced by debris from the 3200 Phaethon asteroid, discovered in 1983, the Geminid meteors were first observed by a British astronomer in 1862, making them the youngest of the annual meteor showers; indeed, most of the other major displays, produced by debris from comets, have been documented for thousands of years (and have likely occurred much longer than that).

The Geminid debris field is the largest that Earth encounters in its annual journey around the sun. Up to 160 meteors may be seen in the course of an hour, seeming to radiate from the Gemini constellation; since they are relatively slow moving (compared to meteors in other displays) and since they tend to leave a vapor trail, the Geminids are also the easiest to observe.

Occurring from December 6 to December 19, the Geminid meteor show peaks on the nights of the 13th and 14…

Backside Blizzard

In the Northern Hemisphere, as storm systems track from west to east, the winds around their center of low pressure move counterclockwise. Ahead of the storm, southerly winds pump warm, humid air into the system, triggering showers and thunderstorms as the cold front approaches. North of the storm's center, this moisture is pulled into cold air behind the front, producing cool rain or snow, depending on the temperature of that air. If the storm is especially strong, determined by the depth of its central pressure, the circulating winds can be fierce and, when combined with snowfall, may produce blizzard conditions on the north and west sides of the system.

The current winter storm, centered over Lake Michigan this morning, is very potent. Its vanguard of showers and mild air flowed across Missouri on Friday, extending into Saturday morning; by Saturday afternoon, cold air was filtering in from the north and, by last evening, snow showers mixed with a gusty northwest wind. The…

Cheshire Moon

Stepping onto the deck last evening, I caught sight of the crescent moon, turned on its back in the western sky. Catching the orange glow of the setting sun and looming just above a branch of our neighbor's tree, it evoked the grin of the Cheshire Cat, Alice's friend and nemesis.

Both enamored with and frightened by the winter night, humans, like Alice in Wonderland, have long confronted its mysteries and threats. Natives of the Tropics, we are poorly equipped to survive the harsh conditions of winter and, devoid of night vision, we remain at the mercy of creatures that patrol its darkness. And the night sky, with its fabulous cast of glowing objects, has long inspired and threatened man, prompting us to imagine figures and omens in its pattern of moving lights.

As the Cheshire Moon dropped toward the horizon, I turned my attention to bright Jupiter, high in the southern sky, and to the other constellations that adorn our winter nights. Despite our advanced scientific know…

Life, Dinosaurs & Time

Life first appeared in Earth's primordial seas some 3.6 billion years ago and evolved into a wide diversity of marine and terrestrial creatures before dinosaurs arose. Unicellular organisms, echinoderms, mollusks, insects, arachnids, crustaceans, fish, sharks, mosses, ferns, conifers, amphibians and many reptiles appeared before the dinosaurs and continue to evolve today.

Dinosaurs ruled our planet throughout the Mesozoic, which stretched from 225 to 65 million years ago (MYA), but other life forms also arose during that Era. Turtles, crocodilians and the earliest mammals appeared in the Triassic Period (225-190 MYA), ancestral birds and flowering plants graced the Jurassic Period (190-135 MYA) and the Cretaceous Period (135-65 MYA) witnessed the rise of ants, social bees, snakes, marsupials and the first deciduous trees.

Since the end of the Mesozoic (65 MYA), when dinosaurs became extinct, these "terrible lizards" live on as birds and Earth's mammals have explode…

Eastern White Pines

It is during the winter, when the deciduous trees are bare, that we pay most attention to the conifers. But, since I park by pickup beneath a large white pine at our Columbia home, I find it hard to ignore this tree in any season. In spring, its small staminate flowers release a copious amount of yellow pollen which coats the truck; soon thereafter the spongy flowers begin to fall, collecting in the bed or along the base of the windshield. Drops of pine sap leave sticky residue on the hood throughout the year and heaps of yellowing pine needles surround the pickup in mid autumn.

Eastern white pines, the largest conifers in eastern North America, are native to southern Canada, New England, Pennsylvania, and the Great Lake States, extending southward along the Appalachian chain. Widely planted as ornamentals, these stately trees were once used for sail masts and are now harvested for lumber or used as Christmas trees. Often growing up to 100 feet tall and possessing a girth that ma…

Evolution of the Sonoran Desert

The Sonoran Desert of the Southwest U.S. and Northwest Mexico is a product of its latitude, the global climate and the regional topography. Lying along one of the desert bands (which run just north and just south of the Tropics), this arid ecosystem receives copious sunshine and is subjected to prolonged periods of high pressure, below which the air is sinking. This atmospheric condition retards cloud formation and both warms and dries the air as it plummets toward the Earth's surface.

Covering a broad basin and surrounded by highlands, the Sonoran Desert is shielded from moisture in all directions; to the northwest are the Sierra Nevada Mountains and the high Mojave Desert, to the north and east is the Mogollon Rim of the Colorado Plateau, to the southeast is the wall of the Sierra Madre Range and, to the southwest, are the mountains of Southern California and the Baja Peninsula. Any air that enters the Sonoran is thus downsloping from higher terrain, causing it to heat up and…

Madagascar and its Primates

As Pangea continued to break apart, Madagascar split from Africa, some 160 million years ago. Drifting to the south, it merged with the remnants of Gondwanaland, the combined mass of Antarctica, India and Australia. There, its African flora and fauna mingled with the plants and animals of that tropical land mass. About 95 million years ago, the India-Madagascar segment broke from Antarctica-Australia, moving to the northeast; within another 15 million years, Madagascar began to rift from India, presumably triggered by an underlying hotspot that also produced the massive Deccan Traps basalt flow at the end of the Mesozoic. By 70 million years ago, Madagascar was moving into prolonged isolation and now rests 350 miles off the southeast coast of Africa.

While the earliest mammals arose during the Triassic, more than 200 million years ago, primates first appeared late in the Cretaceous, after Madagascar had become an isolated land mass. About 60 million years ago, these ancestral pri…

The Voice of Winter

Winter is the quiet season. Compared with the rest of the year, there are relatively few natural sounds that greet us on our excursions through the fields and woodlands. Of course, exceptions do exist: the crunch of snow beneath our boots, the rattling of limbs in the winter wind, the rustling of dead oak leaves and the dreaded sound of sleet, coating our cars and walkways. The wild creatures chime in now and then: the howl of coyotes, the eerie bark of fox, the cheerful tune of chickadees, the drumming of woodpeckers and the raucous cries of jays and crows come to mind. But, for me, the voice of winter is the gruff call of the great horned owl.

Oblivious to the ice, snow and frigid air and well equipped to stalk the long, dark nights, this large and powerful predator symbolizes the harsh winter season and epitomizes the survival skills that it demands. Hidden from view for much of the day, great horned owls appear along wood borders in the gathering dusk, ready for a night of hu…

The Benefits of Aging

Aging has its disadvantages. Our physical strength and stamina tend to deteriorate, we are more prone to a variety of illnesses and, for some, our mental faculties begin to fail. When we reach middle age, we begin to notice the early signs of aging and, combined with the other stressors of that period, this observation can induce a sense of resignation and cause some to give up on the joys of life.

But those who remain active, both physically and mentally, come to realize that there are also benefits of growing older. For most of us, the responsibilities of our career and our family life begin to disipate and we have more time to engage in exercise, hobbies and other personal interests. Those endowed with creativity are especially rewarded by this age-induced freedom; indeed, history is replete with famous writers, painters, photographers and other artisans who took up their passion later in life and, possessing the experience and wisdom of advanced age, were especially productive…

December

A northwest wind developed yesterday afternoon, behind the latest cold front, and, overnight, ushered in the coldest air and lowest wind chill since last winter. December made its appearance beneath a frigid, clear sky, lit by a crescent moon, bright Venus and a bowl of twinkling stars. On my walk to work this morning, it was 22 degrees F.

Festooned with holiday lights and leading up to the beloved season of Christmas, December does not incite the animosity that January and February stir in the soul of tropical man. Nevertheless, in the Northern Hemisphere, December is the darkest month of the year and often brings severe winter weather. Even when relatively mild, the month heralds the long, steady descent toward the nadir of nature's year.

December 1 marks the calendar and meteorologic onset of winter which, from an astronomical point of view, begins with the winter solstice, on or about December 21. One can debate when the season officially begins but, to paraphrase a Supre…