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Showing posts from April, 2007

The Dusk Squadrons

Balmy weather returned to Missouri earlier this week and with it came the chimney swifts. After wintering in Central and South America, these flying cigars return to the U.S. and southern Canada to breed and can be found in most areas east of the Rockies. They were a week late this year, no doubt delayed by the powerful cold front of early April.

Often mistaken for bats, chimney swifts roost in hollow trees, chimneys and abandoned buildings but spend most of the day on the wing, feasting on insects. Come dusk, their forays increase in frequency as mosquitos and other flying insects ascend above the trees. Cruising over our cities and suburbs and communicating with a banter of high-pitched chirps, the swifts resemble squadrons of fighter jets. Their rapid flight is a sequence of fluttering wings and glides, straifing the sky in synchronized formations before veering apart to dive at their unwary targets. Within a week, they will be joined by their larger, more deliberate cousins, …

The Devonian Coast

The Devonian Period, 400 to 350 million years ago, sits in the middle of the Paleozoic Era and is known for its vertebrate explosion. Sharks, boney fish, lung fish and early amphibians all appeared during this time, as did arachnids, terrestrial insects, ferns and the first tree-like plants.

Through much of the Devonian, the Catskill Sea covered most of what is now New York State; indeed, western New York harbors one of the most extensive outcrops of Devonian rocks in North America. This exposure continues along the south shore of Lake Erie, from Buffalo to the Sandusky, Ohio, area. Cliffs of Devonian shale and limestone can be found throughout this coastal region and along the rivers and streams that flow northward into the Lake. Among the more well known Devonian sediments are the Cleveland shale of the Cuyahoga River Valley and the Columbus limestone of the Marblehead Peninsula; the latter also forms the bedrock of Ohio's Lake Erie islands.

The Sierra Batholith

Most of Earth's mountain ranges have resulted either from the collision of plates (the Alps, the Himalayas, the Appalachians) or the development of volcanoes along subduction zones (the Andes, the Cascades). One exception is the Sierra Nevada Range which first developed as an underground tube of magma, known as a batholith.

The first pulse of this molten rock developed within the Smartsville Block, a large exotic terrain that loomed off the west coast during the Jurassic Period, 190 million years ago. This Block fused with the western edge of North America 25 million years later, forming what is now western Nevada and most of California. The second intrusion of magma occured 140 million years ago as an island arc, known as the Coastal Range Ophiolite, collided with the west coast, completing the assembly of central and northern California. The third and final pulse occurred during the Cretaceous reign of Tyranosaurus rex, some 80 million years ago.

The core of the Sierra Nevada…

The Fish Hawk

Thanks to a ban on DDT, ospreys have made a comeback over the past few decades. Now common along coastal areas of the U.S., these "fish hawks" are also regular migrants through the Midwest, heading to and from their Canadian breeding grounds. Along the way, they stop to rest and fish on our larger lakes, rivers and reservoirs and are often spotted in dead trees that overlook the water.

Since they have a white head, ospreys are frequently mistaken for bald eagles; in fact, they are a bit smaller and are easily identified by their dark eye stripe, white underparts and the prominant black patches at the bend of each wing. They hunt by soaring and hovering above the water before plunging talons-first to grab a fish; flying back to their perch to feed, they juggle the fish into a head-first position.

While they inhabit Florida throughout the year, ospreys are summer residents along northern coasts and on large lakes of the Pacific Northwest, Canada and Alaska. They generally mi…

Warbler Season

While birding highlights occur throughout the year, seasoned American birders always look forward to late April and early May, the peak of the warbler migration. These small, colorful insectivores summer in North America but the great majority winter south of the United States. Among the more common Midwestern residents are yellow warblers, northern parulas, common yellowthroats, yellow-breasted chats and Louisiana waterthrushes. Others are fairly common in special habitats; for example, hooded warblers favor mature forest while prothonotary warblers nest in wooded swamplands. Some 18 species summer in Missouri and just as many migrate through the State.

The appeal of warbler watching has to do with their variety (55 species can be found in North America) and the challenge of observing them. Many of these small, active birds feed in the treetops, flitting among the branches to snare their prey. They are thus often difficult to identify, even for the most experienced birders. If …

Hiking and your Health

As a physician, I know that aerobic exercise, such as walking, running, biking and swimming, is good for your health. This type of exercise has been shown to be important in the treatment and prevention of heart disease, high blood pressure, obesity, adult-onset diabetes, constipation, arthritis and osteoporosis. It is also helpful in the management of depression and a variety of stress-related conditions.

As a naturalist, I tend to recommend hiking. This activity combines aerobic exercise with the therapeutic benefits of nature. A frequent patron of multi-use trails, I often wonder about the runners as they labor past me, checking their watches, and the trail bikers who sprint along at high speed or bomb down the winding mountain trails. Neither seem to appreciate their surroundings; they might as well use the city streets or the local stadium track.

While I appreciate the value of competitive sports, I must also recommend the health benefits of a walk in the woods. Nature, in all its …

Earthquake Zones

Earthquakes usually occur along the edge of Earth's crustal plates, especially where they collide (India-southern Asia), subduct (the western coast of South America) or scrape along one another (Southern California). They also occur in rift zones, where continents are being pulled apart (the East African Rift) and around volcanic hotspots (Hawaii).

In some cases, earthquakes occur in mid-Continental areas where one might not expect an unstable bedrock. Such quakes are usually related to the presence of an old suture line (where land masses had fused) or an old, aborted rift. The New Madrid earthquakes of 1811-1812, which altered the course of the Mississippi River, developed along an old, deeply buried rift.

Some areas of the world, located at the conversion of numerous crustal plates, are especially prone to earthquakes. Two of these tectonic bullseyes are Indonesia and Japan; both of these countries straddle four plates (Australian-Eurasian-Philippine-Pacific for Indonesia, E…

Osage Prairie

When white settlers first reached Missouri, tallgrass prairie covered the northern and western portions of the State. In the northern section, the settlers found thick soil, enriched with glacial till; this proved to be ideal for crop production and most of the prairie soon became part of the American Cornbelt. On the other hand, the western section had thin, rocky, unglaciated soil and was used primarily for livestock grazing. As a result, much of this Osage Plain was spared the plow and the majority of Missouri's prairie remnants are found in this area.

One of the better places to experience the tallgrass prairie habitat is at Prairie State Park, 12 miles west of Lamar. Covering 3700 acres, this remote preserve, accessed by graveled roads and a network of trails, offers a true prairie experience. A herd of bison is used to maintain the prairie, which is home to a superb variety of grassland wildlife. Coyotes, red fox, badgers, prairie voles, ornate box turtles, glass liza…

The Oxbow

On this 38th annual Earth Day, there will be a good deal of talk about conservation, recycling and global warming. Unfortunately, talk does not often lead to action. So, it seems appropriate to pay tribute to a group of men and women who took that step and saved a vital piece of wildlife habitat.

West of Cincinnati, the Great Miami River enters the Ohio. Its broad floodplain, a mosaic of ponds, wetlands, riparian woods and cropfields, has long been an important staging area for migrant waterfowl and shorebirds. Subjected to seasonal flooding, especially from late February through April, the shallows of this valley provide rich feeding grounds for these migrants. Other residents and visitors include bald eagles, ospreys, cormorants, herons, egrets, muskrat, beaver and a wide variety of wetland songbirds.

In 1985, area residents learned of plans to construct an industrial port at the mouth of the Great Miami; knowing that this would destroy much of these wetlands, they formed Oxbow, Inc.,…

Grasslands of the Oligocene

While ferns and conifers evolved in the Paleozoic Era and flowering plants appeared by the middle of the Mesozoic, grass is a relative newcomer to the plant kingdom. Grass is thought to have evolved in the rain shadow of the young Rocky Mountains, fostered by a cooling and drying climate.

As the Eocene gave way to the Oligocene Epoch, about 40 million years ago, a period of glaciation began; within 5 million years, glaciation would occur on Antarctica for the first time. The cause for this climate change is uncertain but it is interesting to note that it corresponds to a period of increased volcanism in the Mountain West; in particular, the volcanic San Juans of southwest Colorado began to develop at this time. Whatever the cause, a cooler climate and a reduction of precipitation across the Great Plains both favored the development of grasslands. Persistent wind and intermittent wildfires also played a role and, by the middle of the Oligocene, extensive grasslands covered much of t…

Shorebirds in the Heartland

Most Americans associate shorebirds with southern beaches, having watched them feed along the tidal zone, running ahead of incoming waves. But the majority of these plovers and sandpipers only winter on those southern shores and begin to move north by April. Heading for Arctic breeding grounds, they stop to rest and feed along the way.

Most of these long distance travelers are best found in flooded fields or on the mudflats that line our lakes and reservoirs. Among the more common migrants are black-bellied plovers, greater and lesser yellowlegs, least sandpipers, dowitchers and semipalmated sandpipers. Golden plovers, willets and pectoral sandpipers favor marshy grasslands while phalaropes and western sandpipers feed in the shallows.

Peak shorebird migrations occur from late April through early May. After breeding and rearing their young in the perpetual light of the brief Arctic summer, these nomads are heading south again by early July. Fall migrants may be spotted in the Midwest any…

Backwater Wildlife

Most of our Midwestern reservoirs have a shallow, backwater zone, characterized by flooded timber, marsh and mudflats. Naturalists know that these backwater areas are among the best habitats for wildlife viewing and late April is an excellent time to visit.

Red-headed woodpeckers are usually common in these areas, carving out nest cavities in the drowned trees. In later years, the abandoned holes are used by cavity nesters such as eastern bluebirds, tree swallows, prothonotary warblers and wood ducks. Great blue herons, black-crowned night herons, double-crested cormorants, ospreys and bald eagles also nest in the flooded timber or use the dead trees as rest stops between their fishing runs. Below the surface, the tree trunks attract schools of fish, drawing hooded mergansers, belted kingfishers, pied-billed grebes and, in some areas, river otters to these shallows.

By mid spring, aquatic turtles and water snakes sun themselves on logs that jut from the surface while muskrats feed i…

Tribal Man

Man has always been a tribal creature. The earliest humans, like many animals, formed clans for the purposes of hunting and territorial defense. Later, as man spread across the globe, his disparate populations developed their own physical traits, language, culture and rituals. Today, humans retain their tribal identities: we call them nationality, race and religion.

This week's senseless tragedy at Virginia Tech, covered by every available newsperson in the country, highlights our tribal loyalties. Most of us can personally identify with the scene of the carnage, having attended a U.S. college or as parents/friends of college students. I suspect that many of us were somehow relieved that the culprit was an "outsider," a foreign national who apparently felt alienated in our culture. At least it wasn't one of our own.

Meanwhile, on the other side of our planet, such mass killings are occuring every day, in a war that was instigated by our own tribe. Reports of tho…

April Wetlands

Mid April is a great time to visit Eagle Bluffs Conservation Area, southwest of Columbia. Stretching across the Missouri River Floodplain, this refuge harbors one of the best wetland complexes in the State.

This morning, a lone coyote loped across the entry road, portending another interesting visit to the preserve. American coot, northern shovelers and blue winged teal were abundant, favoring the lake margins, sloughs and flooded fields. Joining them were small flocks of gadwall, green-winged teal and wood ducks. About 200 white pelicans had stopped to rest and feed at the refuge and a large number of double-crested cormorants fished on the open waters or perched on dead cottonwoods that line the larger lakes. Great blue herons stalked the shallows, where muskrat moved among their dens. Noisy as ever, Canada geese had paired off and were nesting along the shorelines.

Hiking atop a levee, I found an excellent variety of songbirds in the adjacent bottomland forest. House wrens and…

The Four Geologic Eras

Geology is a complex and difficult subject, especially for the novice. I recommend that beginners first concentrate on the four major divisions of geologic history: the Geologic Eras. While professional and academic geologists divide the eras into periods and the periods into epochs and these into subdivisions, etc., such classification can overwhelm those who have had no formal education in the field. This blog entry thus provides a basic overview of the four Geologic Eras.

The Precambrian Era (4.6 billion years ago to 600 million years ago) encompasses the great majority of Earth's geologic history, stretching from the formation of our planet to the appearance of shelled marine life. Highlights include the formation of the oceans, the development of the atmosphere and, of course, the evolution of life. The first life forms are thought to have been chemoautotrophic bacteria, which appeared about 3.6 billion years ago.
The evolution of cyanobacteria and photosynthetic algae …

April Nor'easter

After carving a path of destruction across the southern States, our latest "spring storm" turned toward the northeast yesterday and began to move up the Atlantic Coast. Nearing the shore in eastern North Carolina, the storm strengthened, developing a central low pressure typical of a category 2 hurricane. Counter-clockwise winds brought moisture in from the Atlantic, dropping heavy rain from Maryland to Maine.

The heaviest rain fell in New Jersey and New York, with a record deluge of 8 inches in Central Park. Combined with the phenomenal rainfall, onshore winds produced flooding from the Jersey shore to the rocky coast of Maine. Futher inland, where the moist flow met cold air and higher terrain, heavy snow fell across Upstate New York and the Northern Appalachians.

Such "Nor-easters" are most common in November or March, when the jet stream injects cold, Canadian air into the warm, moist air along the Atlantic Coast. The ongoing storm, in mid April, is the product o…

Tectonic Plates

Amateur geologists know that the Earth's crust is a puzzle of tectonic plates and that most of the planet's earthquakes and volcanic activity occur along their margins. But they often assume that the shape of the plates corresponds closely to the contours of our Continents and Oceans. In fact, the seven large plates have both continental and oceanic regions; it is important to realize that the plates are 50 miles thick and that the surface features that we see are but a thin veneer on their upper side.

Africa, Australia and Antarctica all sit near the center of their plates, which extend into the ocean on all sides. On the other hand, some plates are far more complex and their shape is less predictable from the surface features. The North American plate extends from the West Coast of the U.S. to the mid Atlantic Ridge and from southern Mexico to the Arctic Ocean; however, it also extends from the center of Iceland to eastern Siberia, including the Bering Sea, the northeast…

Spring Crossroads

In mid April, the bird population of Missouri is undergoing a dramatic change. Winter residents, such as white-throated sparrows, dark-eyed juncos, fox sparrows and white-crowned sparrows, are departing for the north, never to know the hot, humid summer of the American Midwest. At the same time, summer residents, including brown thrashers, gray catbirds, house wrens, chimney swifts, barn swallows and blue-gray gnatcatchers are arriving from the south and will soon be nesting. Out in the wildlands, migrants are streaming northward, stopping to rest and feed in our State; these travelers include blue-winged teal, American coot, golden plovers, double-crested cormorants and American white pelicans.

Such is the pulse of nature's seasons and birds, more than any other creatures, dance to its rythym.

The Green River Lakes

As the Paleocene gave way to the Eocene, 60 million years ago, a trio of lakes were forming in the intermountain west. Fossil Lake, the smallest but deepest of the three, covered the extreme southwestern edge of Wyoming; Lake Gosiute covered much of the rest of southwest Wyoming while Lake Uinta spread across northeastern Utah and northwestern Colorado. All three of these lakes formed within basins that downwarped as the Rocky and Uinta Mountains rose. Over the course of their history, some 20 million years for the larger two lakes, these bodies expanded and contracted with the climate; during wet periods they were interconnected while, during extended droughts, they were separated by vast salt flats and desert.

Through most of their history, these lakes occupied a subtropical zone and lush vegetation grew along their margins. Crocodiles, turtles, tropical birds, amphibians, lizards and primitive mammals inhabited these bordering wetlands and a wide variety of fish lived within th…

Ponderosa Parklands

Ponderosa pines are common throughout mountainous regions of the western U.S., found primarily in foothill zones, on lower mountain slopes or atop the higher mesas. These large, aromatic conifers favor dry, sunny areas where they grow in open "parklands," interspersed with meadows of grass, forbs and wildflowers.

In Colorado, ponderosa parklands develop at elevations from 6000 to 9000 feet and are especially common across the Front Range foothills, along the Palmer Divide (north of Colorado Springs) and on the southern flank of the San Juan Mountains. A rich understory of Gambel's oak, mountain mahogany, kinnikinnick, wax current and bitterbush lines the drainages, adding to the floral diversity of these scenic woodlands. On shaded, north-facing slopes, where the soil is cool and moist, dense stands of Douglas fir and Colorado blue spruce predominate.

Mid April is a good time to visit the ponderosa parklands of the Front Range foothills. Western and mountain bluebirds …

Forest Wildflowers

April is the month of forest wildflowers. The soil is warming, moisture is abundant and the sparse canopy has not yet shaded the forest floor. So grab your wildflower guide and head for a woodland trail!

Spring beauty, trillium, heptatica, buttercups, bluebells, bloodroot, May apple and Dutchman's britches are among the more common forest wildflowers. Others include wild hyacinth, columbine, trout lily, Jacob's ladder, bellwort, fire pink, rue anemone and squaw-weed. Understory trees, such as redbud and flowering dogwood paint the woodland and the drumming and calls of woodpeckers ring through the early spring forest. By the end of the month, the canopy will close in, shade will envelop the understory and most of the color will fade to green.

Miracles and Nature

On this Christian Holy Day, there has likely been plenty of reference to miracles. But what is a miracle? The word is invoked for an array of unlikely and unexplained events, from the Miracle Mets of 1969 to the mysterious "healings" associated with religious sites. In its most common usage, the word implies Divine intervention, often referring to an inexplicable rescue from disease, injury or death. In such cases, nature is often the villain, whether it be a storm, an infection or an illness (such as cancer) and the saved is either a human or one of his domestic pets. We rarely hear about miracles that saved the lives of wildlife unless, of course, humans were somehow involved.

But that which was unexplained a thousand years ago may be well understood today and that which we currently cannot comprehend may be common knowledge a century from now. The how, when, where and what of our natural world are gradually becoming less mysterious; it is the "why" that ope…

Primates

Primates, the mammalian family of which we are a member, first appeared at the beginning of the Cenozoic Era, some 65 million years ago. Within 5 million years, ancestral primates had diverged into the prosimians (future lemurs, lorises, galagos and pottos) and the anthropoids (future monkeys, apes and humans). Both branches were successful for the next 20 million years but, with the appearance of true monkeys, 40 million years ago, the prosimians began to decline; today, survivors of that group are in isolated areas (e.g. Mada-gascar) or have adopted a nocturnal lifestyle, reducing their need to compete with monkeys.

Apes evolved in Africa 10 million years ago; gorillas diverged from the human line about 9 million years ago and chimpanzees broke away 7 million years ago. Our earliest humanoid ancestors (found to date) are the Australopithecies, which appeared in the Rift Valley of East Africa some 4.5 million years ago; males of these species weighed about 100 pounds, twice as much as…

Spring...Not!

The calendar says it's spring. The grass is green, the flowers are blooming and the trees are leafing out. And it's been in the 70s for the past two weeks. But the jet stream calls the shots and it has brought another round of winter.

A big dip in the jet across the eastern U.S. is allowing cold, Canadian air to pour southward, producing lake effect snows in the upper Midwest and an overnight freeze as far south as the Gulf Coast. In central Missouri, highs are expected in the upper 30s, with wind chills in the upper teens. Overnight lows will be in the low 20s for the next two nights, killing off many of our flowers and blossoms; not good news for the fruit growers!

We humans don't like setbacks. We want our seasonal change to be steady and predictable. Once we've had a taste of spring, winter is no longer welcome. But mother nature is not sentimental....and she has the final say.

Nebraska Sandhills

Representing the largest inland dunefield in the Western Hemi-sphere, the Nebraska Sandhills cover the west-central portion of the State. Viewed from the air, one would expect that they are the remnants of a large lake or sea, their ridges of sand alternating with wetland valleys. In fact, they are a "recent" addition to the landscape, having formed within the last 12,000 years (after the retreat of the Pleistocene Glaciers). Geologists have documented that the dunes were deposited as windblown sand and sit atop rock sediments that can be more accurately dated to the late Tertiary Period. Furthermore, their studies reveal that the dunes have shifted their position a few times; presumably, periods of drought caused the anchoring vegetation to die off and permitted the ever-present wind to move the dunes.

Today, drought-tolerant grasses such as Indian grass, sand love, blowout grass and prairie sand reed stabilize the dunes; cedars also grow on the lower slopes. Any precipitati…

Missouri River Floodplain

Heading north from Kansas City, I-29 rolls across the Glaciated Plain, dropping frequently to cross the many streams that flow westward into the Missouri River. On that warm, sunny morning of April 2, a purple haze of henbit shimmered over the barren fields and small flocks of wild turkey fed among the corn stuble. At one stream crossing, a red-shouldered hawk rose from the valley floor, a four-foot black snake in his talons.

Just south of Mound City, the highway drops onto the Missouri River floodplain, winding northward at the base of the Loess Hills. These heavily dissected bluffs, formed by an accumulation of glacial dust, line the east side of the floodplain from northern Missouri to Sioux City, Iowa; they also rise along the west edge, from Omaha northward. Crossing into Iowa, the interstate leaves the hills and drifts into the middle of the floodplain which has grown to a width of 6 miles at that latitude. Once covered by extensive wetlands, river meanders and oxbow lakes, the r…

Adventure

Having a few days off, I plan to head up the Missouri River to visit a few National Wildlife Refuges in Nebraska and South Dakota. While I'm sure to see plenty of waterfowl, bald eagles, coyotes and other common wildlife of the Plains, I am more excited about what I can't anticipate in advance. Though this is hardly a trip to some exotic land, it is a journey that I have never taken before; new landscapes are certain and unexpected sightings are sure to occur.

The joy of adventure is not knowing what to expect. Those of us in middle age, having eliminated many of our personal unknowns, can be revitalized by new journeys and new projects. Adventure keeps us interested and engaged.