Pied-billed Grebes

While almost never found in large flocks, the pied-billed grebe is the most widespread grebe in North America. This small, stocky bird prefers marshy shallows where it dives for fish and aquatic invertebrates. Easily identified by its short, blunt bill which is marked with a black ring, this grebe is usually seen alone or in pairs; when disturbed, it dives underwater or sinks among the reeds and is rarely seen in flight.

In April, pied-billed grebes are common on Midwest lakes as their spring migration peaks; indeed, seasonal migrations are usually the only time that you will find them in scattered flocks. Breeding across southern Canada, the U.S. and Mexico, they winter on open waters throughout the southern half of the U.S. and Central America; though they prefer fresh water, some may be found on brackish bays during the colder months.

Like most grebes and loons, pied-bills nest on floating mats of vegetation, anchored among cattails or other aquatic plants. The chicks, which have striped plumage, may be seen riding on their parent's back by late spring.

A Gang of Garters

Yesterday's warm, sunny afternoon seemed to be a good time to start the spring yard work. Near some old timbers on the south side of the house, my wife noticed a garter snake; within a few minutes, several more appeared, winding through the leaf litter and among the shrubs.

Garter snakes winter in groups of a hundred or more, usually choosing a cave or den with a south exposure. Come April, they begin to emerge on warm days, retreating to the den at night. Males are generally the first to wander from the winter retreat and are primarily concerned with locating females; early-mid spring is their mating season and they are more active and conspicuous now than they will be for the rest of the year. Yesterday's gang was in constant motion, scouring the area but showing no signs of hunting behavior.

Once the mating season is over, garter snakes become rather solitary and much less active. They are usually discovered while sunning themselves in mid morning and spend much of the day patiently stalking insects, worms, amphibians and small mammals. Fertilization is delayed and the female will give birth to anywhere from 10 to 60 live offspring in late summer; these young snakes are self sufficient from birth and will feast on worms and insects before the mass hibernation begins.

The Baobab Spark

There are moments in our life when we suddenly see our world in a different light, when our perspective changes and our life takes a new course. In my life, one of these moments occurred during the third or fourth grade when, leafing through my first geography text, I came upon the photo of a giant baobab tree. An African family was living in its hollowed trunk and a caption related that this massive "tree of life" provided many of their needs, including food, water, shelter and materials for clothing and rope.

Having a rather sheltered view of the planet at that time, I was fascinated by the photo, the image of which remains clear in my mind almost fifty years later. At that moment, I was seeing a baobab tree for the first time but, more importantly, realized that there were many exotic species and places out there that I knew nothing about. Geography soon became my favorite subject and, over the years, spawned my interest in the varied disciplines of earth science.

Of course, some of us are more receptive to these moments, based on our genes, our experience and the influence of others. But, if we make the effort to look back, we can all remember people, places and events that had a profound impact on our lives. The baobab photo was certainly a spark for me.

The Ringed Planet

Throughout April, Saturn, the sixth planet from our sun, will be high in the night sky. More than 9.5 times further from the sun than is Earth, the ringed planet takes 29.5 years to complete its orbit; on the other hand, Saturn has a rapid rotation, completing its day in 10.5 hours.

One of the gas planets (which also include Jupiter, Neptune and Uranus), Saturn has an equatorial diameter of 74.5 thousand miles, more than 9 times that of the Earth. It is composed primarily of hydrogen and helium, surrounding a core of molten rock; ammonia, methane, water and other compounds are found in lesser amounts. Storms and high winds characterize the atmosphere and, in 2006, the Cassini spacecraft documented the presence of a large, hexagon-shaped, hurricane-like storm over Saturn's south pole.

But Saturn is most famous for its rings, which are composed of ice, dust and rocky debris. While they have a diameter of 150,000 miles, the rings are less than 1 mile thick. Their changing appearance suggests to astronomers that they are relatively young (perhaps less than ten million years old) and that they may have originated from the collision of a comet with one of Saturn's moons. Not to worry: the planet still has sixty moons, half of which are named; Titan, its largest satellite, is the only moon in our solar system to have a significant atmosphere.

The Pantanal

The Pantanal, thought to be the largest, undeveloped wetland complex on Earth, covers almost 70,000 square miles at the junction of Brazil, Bolivia and Paraguay. A desert landscape as recently as 13,000 years ago, this flat ecosystem is now a mosaic of meandering rivers, seasonal lakes, oxbows, sloughs, grasslands, marsh and woodlands. During the wet season, which lasts from October into April, 80% of the Pantanal (Portuguese for wetland) is flooded by its primary streams, which drain the adjacent highlands and distant mountains. With the onset of the dry season, the flora and fauna undergo a dramatic change, augmenting the tremendous array of life in the Pantanal.

Rivaling the diversity of the Amazon Rainforest, this wetland is home to over 700 species of birds, including greater rheas, toucans, macaws, parrots, giant black eagles and, of course, a wide variety of waders. Resident mammals include jaguars, ocelots, maned wolves, giant otters, Brazilian tapirs, howler and capuchin monkeys, giant anteaters and capybaras, the largest rodents on Earth. Anacondas and caimans are among the Pantanal's many reptiles and almost 300 species of fish inhabit its many lakes, streams and seasonal wetlands.

Though "undeveloped," the Pantanal has been used for cattle ranching and is threatened by a variety of human activities. Pollution from upstream mines, human settlements and agricultural areas is perhaps the major threat though deforestation, poaching and unregulated tourism all take a toll. Most recently, plans to divert water from this fragile ecosystem tempt disaster.

Nature's Solar Panels

In the Temperate Zone of North America, April is the month of the leaf. From blades of grass to maple leaves to the giant leaves of the catalpa, nature unfurls her solar panels, converting solar energy to foodstuffs for all primary consumers. The latter include molds, fungi, bacteria, invertebrates and all herbivorous or omnivorous animals, including man. Since secondary consumers (also including man) feed on primary consumers, all terrestrial life is dependent on this annual emergence of leaves.

Despite the vital role that these photosynthetic structures play, nature lovers tend to dwell on flowers, birds and newborn mammals, the traditional symbols of spring. Yet, without leaves, these spring favorites could not exist. More than a conduit for energy trans-formation, leaves absorb carbon dioxide and release both oxygen and water vapor, playing an essential role in the maintenance of our atmosphere.

Beyond their value as producers of food and oxygen, leaves offer shade in the heat of summer, glorious color in the fall, protective cover during winter and vital nutrients for the spring growth of the next generation. More than any other structure in nature, the leaf epitomizes the annual cycle of life.

Thunderstorm Season

Thunderstorms feed on warm, moist, unstable air and are triggered by lift; the latter is provided by an upper level low or an approaching cold front. Such conditions begin to develop along the Gulf Coast States in February and the zone of thunderstorm frequency gradually shifts to the north and west over the ensuing months.

April marks the beginning of the severe thunderstorm season in the Midwest, which will continue through June. As the jet stream moves farther to the north, the Gulf of Mexico "opens up," allowing warm, moist air to invade the Heartland. This provides fuel for the thunderstorms which develop in advance of Pacific cold fronts. In this most common scenario, the storms cluster in swaths, oriented southwest to northeast, and move northeastward ahead of the front. This "training" produces recurrent, heavy rains along the swath, inducing floods; on the other hand, compacted storms tend to be less severe, since rain and "outflow" from the preceding storm cool the air and reduce instability.

The most severe thunderstorms, which often produce tornadoes, are generally isolated "supercells," which form along the "dry line;" this moving barrier separates the warm, humid air ahead of the storm from the cool, dry air behind the front. Energized by the jet stream, these monsters begin to rotate as the southeast flow in the "warm sector" collides with strong west winds at the dry line. Such conditions classically develop across "tornado alley," on the Great Plains, from mid spring through early summer.

Spring Reigns

More than a week after the equinox, spring has taken hold in central Missouri. Forsythias, red maples and wild cherries are blooming and the first crops of henbit, violets and dandelions are brightening the suburban lawns.

Down at the Forum Nature Area, the seasonal lakes have filled with rainwater and the duck-like chortle of leopard frogs has joined the background din of chorus frogs. Eastern bluebirds and tree swallows have paired off and are checking out the nest boxes while clouds of insects, a welcome sight to the phoebes, rise from the shallows.

This morning dawned warm and humid, with a southerly breeze and the threat of thunderstorms. Winter will surely throw a few more jabs our way but, by all accounts, spring has won the battle.

Swallows and Saints

Long before humans inhabited Southern California, cliff swallows returned each spring to nest on rocky bluffs along its streams and rivers. With the arrival of Spanish missionaries, artificial cliffs (mission buildings) began to appear in the rural countryside, offering ideal nest sites for the swallows. The Catholic priests and brothers at the San Juan Capistrano Mission, now in Orange County, observed the seasonal patterns of these birds and, attentive to their religious calendar, noted that they usually arrived on or about March 19, the feast of St. Joseph, and departed for the south on or about October 23, the feast of St. John (San Juan).

The "miraculous" attachment of these swallows to the Mission and their apparent adherence to the feast days eventually caught the attention of the Church, the community and the worldwide media. The fact that they migrated to thousands of other locations across the Continent, arriving and departing on a similar schedule, was apparently irrelevant. Over time, as development closed in on the Mission, it became less attractive to the swallows and their annual treks to and from the site became less spectacular. In an effort to sustain the legend and hold on to tourists, the community has used a variety of measures to attract the valuable birds: artificial nests, mud pools and the release of insects have met with limited success.

Here in Columbia, the tree swallows arrived this past week (as usual) and the cliff and barn swallows will arrive within a couple of weeks. As with all migrant birds, their schedules are closely tied to the solar cycle and, for any given area, their arrival and departure dates are very similar from year to year. Since the Catholic Church has assigned a saint's feast day to every day of the year (excluding major Holy Days), one might always find a miraculous reason for the avian travel dates. In his interpretation of the natural world, man tends to believe what he sees and see what he believes!

Caribbean Subduction Zones

The breakup of Pangea began with the formation of the Tethys Sea during the Triassic and continued with the opening of the Atlantic during the Jurassic. The latter began about 150 million years ago and continues today, pushing the North and South American Plates to the west. The Caribbean Plate, once part of the Pacific, wedged between the two American Plates as they moved westward and began to override them.

Along the eastern edge of the Caribbean Plate, the American Plates are subducting; as these plate margins are forced downward toward the Earth's mantle, they begin to melt, producing volcanism to the west of the subduction zone. This has led to a volcanic island arc (part of the Lesser Antilles), from the Virgin Islands on the north to Grenada on the south; today, 17 active volcanoes dot this island chain. Mt. Pelee, on Martinique, erupted in 1902, killing more than 30,000 people; most recently, the Soufriere Hills Volcano, on Montserrat, has been erupting intermittently since 1995, devastating much of the island and forcing most of its population to leave.

At the west edge of the Caribbean Plate, which includes the Central American countries south of Mexico, the Cocos Plate, a remnant of the Farallon Oceanic Plate, is subducting beneath the west edge of El Salvador, Honduras and Guatemala, producing the volcanic chain that runs along the Pacific coast of Central America. More isolated areas of subduction have occurred along the northern and southern edges of the Caribbean Plate as the American Plates have scraped past; this is especially evident off the north coast of South American, were other islands represent periods of volcanism.

Waves of Thunder

Late yesterday afternoon, a cold front draped across central Missouri, from west to east. As a result, a thick cloud layer formed above Columbia, producing a cold drizzle. Though no lightening or dark skies were visible, waves of thunder rumbled overhead, waxing and waning like the surf on a beach. Checking the local radar, I found that the thunder was originating in large storms to our north and south.

Thunder begins as a shock wave, produced as lightening explodes through the atmosphere. As it propagates outward, the high-frequency sound waves begin to dissipate while the low-pitched sound persists. Nearby cloud-to- ground lightening produces a sharp clap of thunder while thunder from distant storms arrives as a low rumble; in cases where the storm is very distant, the sound wave frequency may be too low for the human ear to detect. Since lightening often develops in a branching pattern (especially in cloud-to-cloud strikes), the sound from its various segments, crossing varied distances, will arrive at our location in sequence, producing a prolonged crackling or rumbling noise.

The persistent rumbling yesterday afternoon likely arose from cloud-to-cloud lightening high in the regional thunderstorms. Numerous branching strikes at high altitude and from distant storms were producing thunder that arrived in Columbia at different times and from different directions. This produced a constant, low-pitched rumble which rose and fell as it was reinforced by new waves of thunder.

Anticipation

March and April can be difficult months in the American Midwest. Periods of warm, sunny weather induce spring fever, only to be doused by the next Alberta Clipper or Pacific Front. Cool, cloudy intervals put thoughts of May on hold and a late snow or killing freeze can annihilate what little progress has occurred. Those with apricot or peach trees (early blooming fruits) are especially keen to these fickle weather cycles.

Unlike wildlife, man is burdened with the capacity for anticipation. We know that warm days and balmy nights lie ahead and often resent the setbacks that nature throws our way. Wild creatures, on the other hand, are content to take one day at a time, governed by instinct and the lengthening daylight. They sense what they must do today, not what awaits them tomorrow. Patience and perseverance are their natural virtues and we would do well to absorb those traits.

A Spring-Fall Mix

It was mild in Columbia last evening, with temperatures in the upper fifties. But the dry air and east breeze made it feel more like early October than late March. Adding to this illusion, a hint of wood smoke was in the air and the squeaky sound of a squirrel gnawing on a walnut husk echoed through the yard. Even the call of a white-breasted nuthatch, though heard year-round, was more reminiscent of fall.

There was little to suggest that spring would soon unfold. The trees and shrubs remain leafless and the greening of the lawn is well behind schedule this year. Turkey vultures drifted through the evening sky but the chimney swifts won't appear for several weeks; the only birdsong was provided by our permanent or winter residents.

But the magnolia buds are swelling, daffodils are blooming and the hysterical call of the flicker rings through the neighborhood. April and the verdant season will soon arrive!

Meeting Stan Freden

In 1980, as we returned from a ski trip to Utah, my wife and I were bumped from our flight and placed on another. Advised to grab any open seats, we settled next to a middle-aged gentleman who occupied my cherished window spot. Taking off from Salt Lake City, I noticed that he was studying the landscape below and I commented on the spectacular scenery, pointing out the High Uintas to our north. His amiable rapport led me into a dissertation on my conviction that air travel is the perfect way to learn geography and that videos, shot from aircraft, should be used in the classroom.

After patiently listening to my bold remarks, he asked me if I had heard of the Landsat Program (I had) and went on to inform me that he was a nuclear physicist who worked at NASA's Goddard Space Flight Center and was one of the authors of "Mission to Earth, Landsat Views the World." Better yet, sensing my interest in geology and geography, he offered to send me a copy; it has been a cherished possession ever since.

The Landsat Program, utilizing advanced satellite imaging techniques, has played an important role in both mapping and the study of our natural resources; geologic mapping, oil exploration, hydrology and the monitoring of vegetation patterns (including desertification and deforestation) are but a few of the disciplines that have benefited from the Program. To have met the Chief Landsat Scientist was truly an honor and this fortunate experience was one of those life events that fostered my enthusiasm for the natural sciences. I sincerely thank Dr. Freden for his kindness and his inspiration.

The Early Flycatcher

Despite the cold, gray, breezy weather, a scattered flock of eastern phoebes turned up at the Forum Nature Area, in Columbia, yesterday. These common, summer flycatchers look like miniature eastern kingbirds and are easily identified by their habit of pumping and spreading their tail after landing on a perch. Best found along the wooded edge of streams and wetlands, they feed primarily on flying insects but, at this time of year, usually settle for larvae, seeds and ground-dwelling invertebrates.

Eastern phoebes are among the first "summer birds" to arrive in the spring, often turning up by mid March. Why they take their chances with the fickle Midwestern weather is a mystery and some undoubtedly succumb to heavy snow, severe cold or ice storms. Those that survive will build nests of mud and straw, which they place beneath rock ledges, eaves, bridges or barn roofs. One must admire their pioneering spirit!

Immortality

Ever since hominids developed the intellectual capacity to fear death, we have sought the key to immortality. Neanderthals were the first of our Genus to bury their dead and early human cultures used rituals and burial artifacts to ensure a safe journey into the afterlife. Even today, many humans are interred with their prized possessions and Churches lure members with the promise of immortality. Focused on the afterlife, religious zealots often fail to experience the many joys of their earthly existence and, in some cases, are willing to martyr themselves (and destroy the lives of others) in pursuit of their spiritual goals.

On this Christian feast of the Resurrection, it is safe to say that science cannot prove nor disprove the existence of an afterlife. On the other hand, we can achieve immortality in ways that all of us have experienced: by passing along our genes, our knowledge, our philosophy, our advice and our love. We will live on in the memories of those we have touched and in the lives of other humans who benefit from our achievements.

A Watershed Journey

Naturalists tend to ignore State and National borders, preferring to view our planet as a mosaic of geophysical provinces. Most of these regions are large and extend across man's artificial boundaries; the Rocky Mountain Province, for example, stretches through Canada, the U.S. and Mexico.

Another way to view the landscape is through its pattern of watersheds. The largest rivers have watersheds that often cover parts of several geophysical provinces; for example, the Missouri River drains part of the Rocky Mountain, High Plains, Central Lowlands and Ozark Highlands Provinces. By dividing these major watersheds into their secondary components, one gains a better appreciation for the complexity of regional topography; if nothing else, watching for these natural boundaries can make your travels more interesting.

Driving from Colorado to Missouri, today, I crossed only two State lines but passed through a series of watersheds. East of Denver, I-70 remains within the South Platte watershed until it crosses the Palmer Divide, north of Limon. Descending southward through the Big Sandy watershed, a tributary of the Arkansas, the highway then turns to the east and climbs 800 feet onto the High Plains escarpment; there it enters the Republican River watershed, which it occupies all the way to Colby, Kansas. Just beyond Colby, the highway crosses an obscure divide to enter the watershed of the Smoky Hill River; this vast drainage, which also includes the Solomon and Saline Rivers, covers much of central and western Kansas. At Junction City, the Smoky Hill and Republican watersheds merge to become the Kansas River watershed; I-70 occupies this drainage as it crosses the Flint Hills, passes through Topeka and continues on to Kansas City. Finally, the interstate crosses Missouri through the primary watershed of the Missouri River, fording its broad floodplain just west of Columbia.

After the Thaw

Another mild and sunny morning sent me down to the South Platte Valley for a hike along the river. The recent bouts of warm weather had opened the valley lakes and the river's winter concentration of waterfowl had clearly dispersed. Small groups of mallards, gadwall and green-winged teal still fed at the margins of the stream, joined by a lone pair of wood ducks; flocks of common mergansers, redheads and ring-necked ducks had moved to deeper waters and could be seen on a large lake just west of the river.

While the grass was greening beneath the cottonwoods, the trees and shrubs remained barren, giving the scene a winter look. On the other hand, the winter silence had given way to a motley choir of magpies, song sparrows, killdeer, kingfishers and flickers. Above it all, a red-tailed hawk cavorted in the early spring breeze and a trio of cormorants headed upstream, back from a winter in the south.

A day after the spring equinox, the South Platte Valley had taken on the feel of a new season. Though spring snows are sure to follow, the thaw is here to stay.

White Ranch Park

One of my favorite destinations close to Denver is White Ranch Park, northwest of Golden. Draped across Belcher Hill and its adjacent ridges, this 3040 acre refuge, a former cattle ranch, includes all of the habitats that characterize the Front Range foothills: ponderosa parklands, spruce-fir forest, foothill meadows and rocky shrublands. The Park is a member of Jefferson County's fabulous Open Space system and is reached via Golden Gate Canyon (just north of Golden, off Colorado 93) and Crawford Gulch Road.

White Ranch, accessed by a fine network of trails, is renowned for its splendid views and for its diverse wildlife population; elevations range from 7000 to 7880 feet. Resident mammals include ground squirrels, Colorado chipmunks, Abert's squirrels, porcupine, fox, bobcats, coyotes, mule deer, black bear and mountain lions; elk also winter at the refuge. Bird life includes golden eagles, wild turkey, blue grouse, Cooper's hawks, Steller's jays, Townsend's solitaires, pygmy nuthatches and both mountain and western bluebirds; winter visitors, such as pine grosbeaks, red crossbills and northern goshawks add to the diversity.

My visit today was greeted by warm, sunny weather and, unfortunately, the infamous foothill winds. As every birder knows, high winds are one of the least favorable conditions for bird watching; but, by heading for the lee side of the ridges, I did manage to see a fair variety of wildlife. Mule deer were common on the brushy slopes and a small herd of elk rested near the edge of a meadow. Several pair of mountain bluebirds had returned from a winter on the southern plains and a lone golden eagle circled above the park. Predictably, mountain chickadees, pygmy nuthatches, pine siskins, Steller's jays and common ravens dominated the bird population.