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Showing posts from October, 2007

Pumpkins

On this day of the Jack-O-Lantern, it is interesting to look at the natural history of pumpkins. Native to Central America, the pumpkin is a member of the genus Cucurbita, which also includes squash, cucumbers and gourds. This genus is complex in that its various species are comprised of some representatives from all of the above groups; in other words, one type of pumpkin may be related to a certain squash but not to other pumpkins. Furthermore, members of the same species group, while designated as pumpkin, squash or gourd, are capable of cross-fertilization.

Current evidence suggests that pumpkins have been used by man for 9000 years or more. Initially collected for their edible seeds and pulp, they were eventually cultivated and, by the time European explorers arrived, their shell was being used to construct mats. Classified as a fruit, the pumpkin is an annual vine squash which produces both male and female flowers on the same plant. Early in the growth cycle, only male flow…

Fishing Frenzy

One of the highlights of my recent trip to Longboat Key was the development of a feeding frenzy on Sarasota Bay. The event began when a scattered group of Forster's terns discovered a large school of fish near the surface. Their chatter and repeated dives attracted the attention of brown pelicans and at least twenty soon joined the feast; though they usually dive from ten feet or more, the plentiful bounty allowed the pelicans to feed by rising only a few feet and then lunging forward, scooping fish into their net-like bills.

Opportunists that they are, laughing gulls moved in from all directions, raising the noise level with their piercing calls; some picked small fish directly from the surface but most settled next to the pelicans, waiting for a meal to drop from their pouch. Double-crested cormorants also joined the fray, diving from the surface to catch their prey, and a pair of belted kingfishers flew in from the nearby mangroves, their distinctive chatter adding to the din…

Quarryland

Enroute to Tampa last week, my flight made a stop in Louisville, Kentucky. As we descended across the forested hills of southern Indiana, I was delighted by the autumn colors and amazed by the large number of quarries that dot the landscape. This is, of course, limestone country.

Traveling east to west across the southern half of the Hoosier State, one encounters bedrock that gradually decreases in age. The southeast corner of Indiana sits atop Ordovician shales and limestones; further to the north and west, these give way to Silurian dolomites and then a band of Devonian sediments. In south-central Indiana, Mississippian limestones dominate the scene, including the famous Salem Limestone (commonly referred to as Indiana Limestone); deposited in a shallow sea, 340 million years ago, this exceptionally pure and workable stone has been used to construct many of America's landmark buildings, including the Empire State Building. Forming a jagged swath from northwest of Bloomington to s…

Flying South

Like many birds, I will be flying south this weekend. But, unlike the feathered travelers, I will be coming back next week. And, as one who prefers seasonal change to year-round heat and humidity, that's fine with me.

While I always enjoy a visit to our place on Longboat Key, off Sarasota, a week or two of summer like conditions is more than enough to make me yearn for cool, dry air. I have not been a summer person since I turned in my lifeguard whistle, 35 years ago, and, the older I get, the less I tolerate the Midwest steambath. Which explains my fondness for our Colorado farm!

But Florida can be a fascinating place to visit, with its subtropical foliage, diversity of birdlife and unique fauna. For anyone who has an interest in meteorology, it also offers an awesome mix of cloud formations and thunderstorms. And, of course, a daily walk on the beach can be good for the soul!

April in October

Yesterday felt more like late April than mid October. A potent Pacific storm had pulled out of the Rockies and, by late afternoon, was centered in southwestern Nebraska. Its associated cold front stretched from northern Minnesota to northern New Mexico and, ahead of the front, warm, moist air streamed northward from the Gulf, pushing highs into the 70s as far north as Chicago and Detroit.

As the front nudged eastward, bands of thunderstorms developed across the Southern Plains, moving northeastward and spawning at least 17 tornados in Oklahoma and Missouri. Further east, the southerly flow was bringing much needed rain to the lower Mississippi and Ohio Valleys.

By this morning, the central low pressure was in northwestern Iowa and continued to creep to the northeast. The squall lines have shifted east of the Mississippi River and beneficial rains were moving into Alabama and Tennessee. Since the center of the storm is well north of Missouri, our "backside" winds are from …

Rocks on Ice

Those of us who have hiked through forest or traveled across plains in the northern U.S. or Canada have occasionally noticed a large rock or boulder that seemed totally out of place. Surrounded by trees or half-buried in the soil, these monoliths appear to have either risen from the ground or dropped from the sky. On closer inspection, we find that their composition (usually igneous or metamorphic) is different from other rocks in the area.

These alien boulders are "glacial erratics," having been transported to their current location by the Pleistocene glaciers. Wrenched from a mountainside or scooped from the bedrock, they were carried atop or within the Ice Sheet as it advanced southward and then released as the glacier melted back. Often transported hundreds or even thousands of miles, these massive rocks are a testament to the power of flowing ice. Found across the glaciated areas of North America, they are but the largest and most obvious component of glacial cargo; smal…

Isolation Lost

The land that would become New Zealand formed along the western coast of Gondwanaland throughout the Paleozoic Era. Beginning 500 million years ago and ending 100 million years ago, recurrent episodes of deposition, compression and uplift added this land to the great Southern Continent. Then, about 85 million years ago, future New Zealand was torn from Gondwanaland as the Tasman Sea began to open, triggering the Island's long period of isolation.

From 55 to 25 million years ago, the ocean gradually opened between Australia and Antarctica; this process increased tectonic forces in New Zealand, which lies along the boundary of the Australian and Pacific Plates. The North Island sits above the edge of the Australian plate; subduction of the Pacific Plate below the Australian Plate in this area has produced volcanism across the North Island. New Zealand's South Island, on the other hand, straddles the two plates and the prominant Alpine Fault marks the boundary; compression eas…

The River Otter

As the days shorten and the weather begins to cool, most of us feel energized and become more active. This is also true for wildlife; stirred by the autumn chill and driven by the need to prepare for the winter months, many of our native mammals become restless, and thus more visible, during the waning days of fall. What better time to set out in search of one of our more interesting and entertaining residents, the river otter?

A member of the mustelid family, which includes badgers, mink and weasels, river otters were once common along most wooded streams in North America. Though extirpated from many areas during the 1800s, they are now making a gradual comeback due to hunting restrictions, habitat restoration and reintroduction programs. Nevertheless, "development" and pollution remain a threat in most regions.

River otters favor woodland rivers, lakes and swamplands where they feed primarily on fish, crustaceans and amphibians; on occasion, they also consume aquatic bir…

Red Heads

Found throughout southern Canada and the eastern two-thirds of the U.S., red-headed woodpeckers favor open woodlands. While often seen on farmlands, orchards and rural parks, these attractive birds are especially common on floodplains and in the backwater areas of our larger lakes and reservoirs; there they find stands of dead trees in which they prefer to nest. Once abandoned, their nesting cavities are used by tree swallows, bluebirds, prothonotary warblers and starlings.

Easily recognized by their bright, red head and large white wing patches, these woodpeckers have a varied diet. While feasting on bark insects like most of their cousins, red heads also "flycatch" from fence posts or dead snags, generally pursuing larger insects such as mayflies, damselflies and cicadas. And, like flickers, they often feed on the ground, consuming ants, beetles, grasshoppers, nuts and fallen fruit. Finally, like their western cousin, the acorn woodpecker, these versatile birds cache a…

Collision Zone

Looking at the weather map this morning, sunny skies dominated the Northeast, Southeast, Southwest and Northwest. But here in the Heartland, a large swath of showers and thunderstorms covered eastern Kansas and much of Missouri. Though no major fronts are moving across the region, light winds from the surrounding areas are converging over the Central Plains.

High pressure over the Northwest and a low pressure system over the Northeast are pumping cool, dry air southward across the Northern Plains. Conversely, low pressure over the Southern Plains and high pressure over the Southeast are combining to produce a flow of warm, humid air from the Gulf of Mexico. While pressure gradients are low and the winds are weak, these moving air masses are merging along the Kansas-Missouri axis, producing a concentrated area of heavy rain and thunderstorms.

Since there are no strong fronts or steering winds in the region, this blob of precipitation is moving very slowly, waxing and waning as it cr…

Life in Perspective

Current scientific evidence indicates that life first appeared on Earth 3.6 billion years ago. To put this evolutionary span in perspective, it is helpful to telescope the entire process into a single year. By doing so, 1 day represents 10 million years, 1 hour covers 417,000 years, 1 minute spans 6950 years and 116 years flash by in 1 second.

Using this condensed calendar of life, chemoautotrophic bacteria, feeding on sulfides and other organic chemicals, develop along the mid-oceanic ridges early on January 1. By January 10, stromatolites of photosynthetic cyanobacteria appear in shallow bays across the globe. Eukaryotic cells, which contain cytoplasmic organelles, turn up by mid June and multicellular algae have evolved by late September. Complex, soft-bodied organisms, such as sea worms, jellyfish and soft corals evolve in late October and, by November 1, shelled marine life has appeared.

Early in November, star fish, mollusks, sea urchins and trilobites scour the ocean floor and ja…

Couteau des Prairies

The Couteau des Prairies (Highland of the Prairie) is a 200 mile swath of Precambrian Sioux Quartzite, stretching from eastern South Dakota, through southwestern Minnesota and into extreme northwestern Iowa. Remnants of an ancient mountain range, this hard, metamorphic rock was deposited 1.5 billion years ago and has since undergone compression by overlying Paleozoic-Tertiary sediments, uplift, erosion and both sculpting and burial by the Pleistocene Glaciers. Even now, numerous streams erode the plateau, which divides the watersheds of the Missouri and Mississippi Rivers.

Today, the Couteau stands out as a network of ridges and low plateaus, rising 500-800 feet above the surrounding plains. Cliffs of the Sioux Quartzite are exposed throughout the uplift but, in many areas, are buried by up to 700 feet of glacial drift (both till and wind-blown loess). Buffalo Ridge forms the crest of the uplift, rising to nearly 2000 feet; it is composed of Cretaceaous shale and sandstone overlying th…

J.T.'s Gaia

As a fan of James Taylor since the late sixties, I have found that his lyrics always capture the essence of human nature. And, as a naturalist, his song "Gaia," on the "Hourglass" CD, is my personal favorite.

Decrying man's obsession with technology and his intent to "tame nature," the song also takes aim at our presumed rights as God's "chosen" species. At the same time, Gaia expresses a reverence for the beauty and harmony of the natural world and encourages the listener to step back from our narrow and self-righteous view of man's role on this planet.

I could continue to write these blogs for another twenty years and still fail to express the naturalist philosophy as effectively as this single song does. My thanks to James Taylor for a beautiful and inspiring work of art.

A Silent Front

A cold front pushed through the Midwest yesterday but, except for some clouds and a wind shift, was barely noticeable in central Missouri. While most cold fronts arrive with blustery conditions, accompanied by rain, thunderstorms or snow, yesterday's mellow transition was due to several factors.

The center of the storm was up in Minnesota and its low pressure zone was broad; in addition, it was not energized by the jet stream and was drifting slowly to the east. Its trailing cold front was likewise sluggish and separated two air masses that differed little in temperature and humidity. As a result, the passing front was only marked by a band of clouds, a few scattered showers and a gentle north breeze.

The more typical cold front, attached to an energized, "tightly wound" center of low pressure, arrives with a bang, as disparate air masses collide and cold, dry air undercuts warm, humid air ahead of the front. Significant pressure differences across this moving barrier gene…

Terminal Moraine

New England harbors the greatest concentration of glacial terrain in the eastern U.S. and one of its most striking features is the terminal moraine of the Wisconsin Glacier. As the last of the Pleistocene Ice Sheets formed across northern Canada and Europe, water was locked in the glaciers and sea level dropped; at the peak of the Wisconsin Glaciation, the coast of the New England mainland was at least forty miles east of its present-day location.

As the Glacier plowed its way to the south and east, it sculpted the peaks and valleys of the Northern Appalachians and hauled the remnant debris toward the coast. Reaching its maximum extent some 23,000 years ago, the lobulated Ice Sheet produced a ridge of till, rocks and boulders along its outer edge; some of this debris had been plowed along in front of the glacier while the rest was dumped by meltwater flow atop and within the ice. As the Glacier retreated to the north, it left behind this "terminal moraine," which rose above t…

The Powerline Falcon

Of the five falcons that inhabit North America, the American kestrel is the most common and the most widespread. This small raptor, formerly known as the sparrow hawk, favors open country where it often perches on powerlines, surveying the ground for insects, lizards, mice and songbirds. At other times, it hovers above the ground before striking.

Found throughout the lower 48 and southern Canada, the kestrel, about the size of a jay, is easily recognized by its distinctive facial markings and the rust color of its back and tail feathers. Though small, this swift predator is hardy, staying through the winter in most of its range; those that inhabit southern Canada and the northern U.S. do move southward for the colder months and, as a result, kestrels are most common in the southern U.S. during the winter. Drive any open-country road from October through April and you will see a kestrel every mile or so, perched on a powerline or small tree; they are also fairly common in suburbs and ur…

Autumn Wanderers

The words "autumn migration" bring to mind flocks of waterfowl, pods of whales and herds of large herbivores such as elk, reindeer or wildebeest. But, on a much smaller scale, our local wild creatures are also wandering about, preparing for winter.

Anyone who travels the backcountry in October will see a large number of box turtles, crossing the treacherous roadways as they search for food and wintering sites. Over the next few weeks, they will feast on berries, mushrooms, succulent plants, insects and earthworms as they prepare for a winter beneath the soil. In like manner, small mammals such as raccoons and opossums, having dispersed from their family groups, wander through the countryside, putting on fat and searching for winter dens.

Hikers who venture out on rainy autumn days may also encounter large, yellow and black salamanders along the trails. Unlike their reclusive cousins, these eastern tiger salamanders leave their summer digs to search for a pond in which to w…

Life on Earth

As I walked to work this morning, Venus gleamed below a crescent moon and stars faded in the predawn light. For those who know what their looking at, there is nothing more spectacular, nor more humbling, than the night sky.

Going about our short lives, focused on our personal needs, our families, our jobs and the events on this planet, we seldom stop to ponder our place in the Universe. Trying to make a difference in our own "world," we forget that we live on a smallish sphere that circles a medium sized star on an outer arm of a galaxy which is composed of billions of stars and which, itself, is one of billions of galaxies. Earth is but a grain of sand on the vast beach of the Universe and our lifespan is but a fleeting second in its history.

Yet, we persist in our efforts. We try to enjoy the time that we have, plan to experience the many wonders of this planet and do what we can to make it a better place. Afterall, it is our home. The night sky will always be there to keep …

Western Trough

The first wave of winter has pushed into the lower 48 as a pro-nounced dip in the jet stream has developed over the western States. Curving from the Pacific Northwest to the Four-Corners region and then northeastward across the Rockies, this steering current has brought cold, Canadian air to the Intermountain West. Snow is falling in the mountains and many of the Great Basin cities have experienced their first hard freeze of the season.

Meanwhile, ahead of the trough, summer has returned to the High Plains and Midwest, with afternoon highs in the mid to upper 80s. As it moves eastward, the trough is forecast to "flatten out," keeping the cold air along the northern tier of States. Here in Missouri, southerly winds will bring a warm, humid flow from the Gulf of Mexico, producing conditions more typical of June than October. Should the cold air get close enough, atmospheric instablity and afternoon thunderstorms will develop, enhancing the illusion of summer. The battle of the …

Seals and Bears

In recent decades, the study of evolution has been greatly advanced by the use of DNA analysis. Formerly based on fossils, geology, modern observations and a good deal of speculation, we now find that some of our past evolutionary assumptions were incorrect. But such is the history of science; as new information and tools become available, our knowledge and our theories change.

Watching sea lions romp in the surf, one might naturally assume that they are most closely related to otters; and who hasn't thought of a walrus as they watched a manatee loll among the sea grass? In fact, as DNA studies have shown, pinnipeds (seals, sea lions and walruses) are most closely related to bears, having diverged from a common ancestor some 25 million years ago. Manatees, on the other hand, are related to elephants and cetaceans (whales and dolphins) diverged from cows and pigs about 50 million years ago.

Of course, many humans dismiss the idea of evolution altogether. For them, the story of N…

Bugles of Autumn

As the first autumn snows dust the higher peaks, the Rocky Mountain elk begin their descent to wintering valleys. Along the way, their annual rut begins and the bulls attempt to gather their harems. Using high-pitched bugles to attract females and to keep rivals at bay, the 750 pound males become frenzied for the next few weeks, foregoing food and sleep to keep their harem intact and to ensure propagation of their own genes.

The rut peaks in early October as the elk are settling into their winter homes, usually montane meadows between 7500 and 9000 feet. One of the best areas to observe this rite of autumn is Rocky Mountain National Park, northwest of Denver. Viewing (and listening) is best at dawn and Horseshoe Park, just a few miles west of the Fall River entrance (along U.S. 34) often provides the best show.

Once the rut is over, mixed herds of a hundred or more gather for the winter. Grazing on meadows in the early morning and late day hours, the elk retreat to nearby woodlands for …

The Joy of October

Many people have their favorite month and I suspect that most naturalists would pick October; it is certainly my choice! With its mild, sunny days, cool nights and colorful foliage, October is the ideal month for hiking. Linking summer and winter, October brings a tide of migration as elk, songbirds, whales and waterfowl head for wintering grounds; hibernators, stirred by the autumn chill, also become more active and visible as they feast on a bounty of nuts, berries and salmon.

In the western mountains, the first significant snowfalls brighten the peaks while a dropping jet stream brings regular cold fronts to the Midwest and Northeast. By the middle of the month, wetlands fill with ducks and geese and the hooting of owls greets the night. And, as humidity, insects and yard chores fade away, it is hard to resist those nature trails. October is the outdoors month!