Thursday, July 31, 2008

Heat Waves and Global Warming

As the extreme heat expands eastward over the next few days, the subject of global warming will, not doubt, get plenty of air time. How soon we forget the chilly spring of 2008, which put Midwestern flora two weeks behind schedule!

While there is plenty of evidence that Earth's climate is gradually warming, regional heat waves have no relationship to that global phenomenon. Rather, like other local weather patterns (e.g. the excessive snow and rain in the Upper Midwest), they are a product of ocean currents and jet stream patterns. Indeed, one area of extreme weather often lies adjacent to an area that is experiencing the opposite conditions (e.g. the coexistence of Midwest flooding and the Southeastern drought); such opposite extremes are usually separated by a persistent frontal boundary that, itself, is governed by a stable jet stream.

Once again, our short life spans and inability to take the long view make us jump to the wrong conclusions. We focus on current weather records (and assume that they forecast a climate meltdown) while overlooking the fact that the previous record occurred a century ago! Despite this mid summer heat wave (not terribly unusual) we could easily face record cold next winter. By then, thoughts of global warning will be suppressed (if not welcomed).

Wednesday, July 30, 2008

Big Oak Tree

Before the arrival of white settlers, a vast swamp forest covered most of the Mississippi floodplain. The fertile soil supported the growth of huge trees, dominated by water-loving species such as burr oak, sycamore, silver maple and bald cypress. By the 1930s, timber production and drainage for agriculture had destroyed most of this rich forest and only scattered remnants persist today. Big Oak Tree State Park, in southeast Missouri, protects one of these, a 1007 acre stand of virgin swamp forest; the park is west of Missouri Route 102, 11.3 miles south of East Prairie.

Accessed by a boardwalk trail, the woodland harbors twelve State Champion Trees, two of which are National Champions. Permanent avian residents include pileated and red-headed woodpeckers, hooded mergansers, barred owls and wild turkey; during the warmer months, they are joined by hooded and prothonotary warblers, Mississippi kites, common yellowthroats, fish crows and Louisiana waterthrushes. The Park is one of the best places in Missouri to find Swainson's warblers, which nest in stands of giant cane that dot the understory. Mink, raccoons, white-tailed deer and river otters are among the floodplain mammals.

The loss of swamp forest and marshlands along the Mississippi has reduced the ecological diversity of the floodplain, eliminated the natural filtering that wetlands provide and increased the risk of flooding in other low-lying areas. Furthermore, the agricultural lands and industrial ports that have replaced them are a steady source of pollutants that make their way into the River and, eventually, into the Gulf of Mexico. Naturalizing the floodplain, to the extent possible, is an essential step toward restoring this vital ecosystem.

Monday, July 28, 2008

Dolly's U-Turn

As Hurricane Dolly made landfall in South Texas last week, a dome of high pressure was forming over the Southern Plains. Following the outer rim of that dome, Dolly moved westward into Mexico and then northwestward, stalling in southeast New Mexico and producing floods across that region. Over the past 24 hours, the storm remnants have drifted northward and the central low pressure now sits above the westernmost panhandle of Oklahoma, bringing upslope rains to the Colorado Front Range.

As Dolly continues to skirt the dome of high pressure, air within the dome is sinking, producing extreme heat across northern Texas, Oklahoma and Arkansas. By mid week, a Pacific cold front, moving down from the northwest, will sweep the remnant moisture of Dolly into the Heartland, producing storms across Kansas, Iowa and Missouri. Unfortunately, for residents of the Southern Plains, the high pressure dome will hold, the heat will persist and Dolly's final gasp will push off toward the Upper Midwest.

Sunday, July 27, 2008

Springville Marsh

At the end of the Pleistocene Ice Age, a vast wetland, known as the Big Spring Prairie, covered much of northwestern Ohio. Today, Springville Marsh, a State Nature Preserve, protects a 160 acre remnant of that ecosystem; characterized by flat terrain and abundant ground water, this relic has survived drainage, forest encroachment and the farmer's plow.

Accessed by a 1-mile trail, most of which crosses the marsh as an elevated boardwalk, this fascinating preserve is on Township Road 24 (west of U.S. 23), 4 miles north of Carey, Ohio. Visitors will find an extensive cat-tail marsh, with patches of twig rush, sedge and phragmites; islands of willow and shrubby dogwood dot the wetland, adding to the floral diversity. Rare species, such as Kalm's lobelia, bottle gentian, shrubby cinquefoil and fen orchids may be seen along the boardwalk.

Wetland residents include a variety of herons, egrets, soras, mink, long-tailed weasels, raccoons and red fox; spotted turtles, threatened in Ohio, may also be found. Open ponds, viewed from a duck blind or observation tower, attract a variety of waterfowl, especially during spring and fall migrations.

Saturday, July 26, 2008

The Pliocene

The Pliocene, the last epoch of the Tertiary Period, stretched from 10 to 2 million years ago. As it began, the Rio Grande Rift was forming in Colorado-New Mexico and the Tetons rose in Wyoming. Other geologic highlights of this Epoch included the formation of the Galapagos Islands (8 million years ago), the development of the San Francisco volcanic field of northern Arizona (6 MYA), the sculpting of the Grand Canyon (which continues today), the arrival of the Salinia Terrain (now Southern California), the formation of Kauai (5 MYA), the opening of the Gulf of California, the development of Oahu (4 MYA), the rise of the Sierra Batholith (which continues today), the arrival of Panama to connect North and South America, the formation of the Long Valley volcanic field in California, the appearance of Easter Island (3 MYA) and the opening of the Lake Baikal Rift (2.5 MYA).

New life forms of the Pliocene included sheep, goats, cattle, antelope and bison in Eurasia, mammoths in Africa and megatherium, a giant ground sloth, in South America; sea lions, seals, walruses and saber-toothed cats also appeared during this Epoch. Gorillas split from the human ancestral line 9 million years ago and chimpanzees followed two million years later.
Australopithecus, thought to represent the earliest hominid, appeared in the Rift Valley of Africa 4.5 MYA, followed by Homo habilis 2.5 MYA; the latter species had opposable thumbs and was the first hominid to use stone tools.

Toward the end of the Pliocene, Earth's climate was cooling. An ice cap had formed over the North Pole and glaciers appeared on Greenland. The stage was set for the Pleistocene Ice Age, which began about 2 million years ago; many climatologists believe that the Holocene, in which we live, is just a warm interglacial period of the Pleistocene and that another phase of glaciation will develop in 5-10 thousand years.

Friday, July 25, 2008


Estivation is essentially hibernation during periods of excessive heat or prolonged drought. An adaptation to environmental stress, this physiologic response is especially common in desert regions and in geographic areas that are characterized by dry seasons.

Land snails, terrestrial crustaceans and a wide variety of amphibians and reptiles are known to estivate. More than a retreat to cool or moist dens, this process involves a down-regulation of the animal's metabolism to preserve stored energy until environmental conditions improve. Many amphibians and invertebrates also secrete a membrane that protects them from dehydration through the estivation.

While many mammals den up during periods of excessive heat or drought, only a few species are known to estivate. Humans, of course, adapt to seasonal change with our various technologies but some of us (myself included), not being fans of hot weather, would love to estivate now and then.

Thursday, July 24, 2008

Northeast Deluge

While the weather news was focused on Hurricane Dolly yesterday, a perfect rainmaker was developing across the Northeastern States. A cold front, stretching from the mid Atlantic region into New England, was attached to a potent but slow moving storm system, centered just north and east of the Great Lakes.

In concert, high pressure off the mid Atlantic coast was pushing in copious moisture from the ocean, including the tropical remnants of Cristobal. Encountering the cold front, this warm, saturated air was forced to rise, producing a chain of heavy thunderstorms along the front, which crept slowly to the east. Some storms dropped rain at rates of 3-4 inches per hour, triggering flash floods throughout the region.

This morning, the front was hugging the eastern shore, from Philadelphia to Boston, producing travel nightmares across the most populated swath of our country. Though Dolly is more powerful and destructive, the Northeast storm is likely to have a greater impact.

Tuesday, July 22, 2008

Dolly Watch

The Weather Channel, starved for tropical excitement over the past two years, is surely thrilled to have Tropical Storm Dolly spinning in the Gulf of Mexico. As one might expect, Jim Cantore, their superstar storm chaser, has been dispatched to Corpus Christi, Texas, to stand in the wind and rain as Dolly makes landfall. Unfortunately, as is often the case, the storm seems to be veering west of the forecast track and Jim may be heading for Brownsville to stay in the action.

Still expected to strengthen into a low level hurricane, Dolly will likely miss the oil and gas platforms of the northern Gulf but there is still hope that its remnants will bring drought relief to southern Texas. Should the storm move far enough to the north to threaten South Padre Island and Texas coastal cities, it will get front page billing in U.S. newspapers; should it stay south and wreak havoc on Mexican fishing villages, look for the story on page two or three.

Monday, July 21, 2008

Birding the Treetops

While it is relatively easy to observe birds that feed on the ground or in low shrubs, it can be a challenge to identify species that inhabit the forest canopy. Scarlet tanagers, wood pewees, red-eyed and yellow-throated vireos, olive-sided flycatchers, crossbills and many warblers are among the birds that tend to favor the treetops.

Novice birders are often frustrated by these species and even veteran bird watchers find it difficult to observe canopy birds without getting a serious case of neck strain. One of the better ways to solve this problem is to find a birding location that offers a view across (or even down to) the forest canopy. Rocky outcrops on the rim of a gorge or clearings on a wooded hillside are two examples. Such vantage points offer a comfortable and unobstructed view of the treetops and foster the patience that is often required to observe and identify these species. Of course, many parks and nature centers provide observation towers that serve the same purpose.

Saturday, July 19, 2008

July Soup

After five days in the thin, dry air of Colorado, I have returned to the hot, muggy summer of the American Midwest. Though the intense sunshine of the Front Range often produces afternoon highs in the 90s, the high elevation and thin atmosphere promote rapid cooling at night and early morning lows drop into the 50s. By contrast, the thick blanket of humid air in the Midwest serves to minimize the radiation of heat and we awaken to temperatures near 70.

By mid July, the jet stream has moved into Canada and high pressure builds across the Southern Plains. Pacific storms and their associated cold fronts are diverted across the northern tier of States and precipitation in most of the Central and Eastern U.S. is limited to scattered, pop-up thunderstorms and the occasional tropical system. At the same time, this high pressure over the plains is partly responsible for the seasonal monsoon of the Southwest, pulling Gulf moisture across Mexico and into the Four Corners region.

The sultry conditions will persist until the jet stream drifts southward, allowing pockets of cool, Canadian air to invade the Heartland. Though storms across the northern States may send weak cold fronts into the Midwest, significant, lasting relief must await a buckling of the jet stream itself. Don't count on that until mid September or so!

Friday, July 18, 2008

The Pope and Global Warming

Pope Benedict, in Sydney, Australia, for a Catholic Convention, is receiving a great deal of attention for his concern about global warming. Exhorting his flock to combat the problem, he places emphasis on the conservation of natural resources and on efforts to reduce our production of greenhouse gases. But, in a rush to label him "the first Green Pope," reporters and admirers overlook the fact that his Church's stance on birth control is one of the key impediments to effectively dealing with this threat.

To the extent that humans are responsible for climate change, the unchecked growth of our population, especially in developing countries, is a primary factor. Technology and conservation measures will not be successful unless combined with efforts to reduce human population growth. If the Pope is truly alarmed by the prospects of climate-induced catastrophe, he would best serve our species and our planet by reversing the antiquated teachings of his Church.

Thursday, July 17, 2008

Singing in the Heat

On hot, summer days, bird song is generally subdued. The high-pitched twitter of chimney swifts, brief tunes from the ever-cheerful chickadees and the buzzy chatter of house wrens are some of the few calls that pierce the oppressive heat. But, as is always the case in nature, there are exceptions.

This summer, a flock of lesser goldfinches has settled at our Littleton, Colorado, farm for the first time. Common across the foothill canyons and shrublands, they are much less common on the adjacent Piedmont and we are about five miles from the base of the mountains. For the past few days, the colorful males have been singing from dawn to dusk, indicating that their breeding season is underway. Like their cousin, the American goldfinch, this western species nests in the summer, timing the process with the peak availability of favored seeds (especially thistle); they also use thistle down to line their cup-shaped nests. While adults feed on both seeds and insects, the nestlings rely on a fresh crop of soft, immature seeds (hence the importance of timing).

Most species that inhabit hot, dry environments concentrate their activity during the morning and late daylight hours, retiring to cool, shaded areas during the heat of the day. But when breeding season arrives, these finches seem oblivious to the conditions; some instincts are stronger than others!

Wednesday, July 16, 2008

March of the Collared Dove

The Eurasian collared dove, a native of India and the Middle East, had spread into Europe by the early 1900s; within another fifty years, it was living and breeding as far north and west as Scandinavia and Great Britain. Released in the Bahamas in 1975, this prolific bird invaded South Florida by the early 1980s and quickly spread through the Southeastern States. Today, small populations have been found as far west as California.

It is now clear that this hardy dove is rapidly becoming a common, widespread resident of North America, matching the success of the maligned European starling. Collared doves were first reported in southeastern Colorado in 1996 and quickly colonized most towns across the State's eastern plains. Sizable populations began turning up in Front Range cities over the past few years and, for the first time this summer, I encountered a breeding pair on our Littleton farm.

Larger than mourning doves, this immigrant may have a negative impact on native bird populations though evidence is lacking to date. Concerned that the collared dove may be a problem in agricultural areas, the Colorado Division of Wildlife has established a Eurasian collared dove hunting season from December through February, with no bag limit; this is in addition to the standard September-October dove season. The winter hunt will occur after the native doves have moved south of Colorado, thereby minimizing impact on those species; the hardy collared dove does not migrate but, like most doves, gathers in large flocks during the colder months.

Tuesday, July 15, 2008

Vertical Birding

One of the many good things about living at the base of a mountain range is that a whole series of life zones lie within a short distance. Each life zone has its own unique population of flora and fauna and, for the naturalist, there's nothing more inviting. Birders are especially rewarded by such geography and the Colorado Front Range is certainly one of the better bird watching areas in the country.

Facing another day in the 90s, I decided to head for higher and cooler terrain, leaving our Littleton farm just before 7 AM. My first stop was at Deer Creek Canyon Park, southwest of Denver; its parking area and lower trails lie within the foothill shrublands at an elevation of 6100 feet (700 feet higher than our farm). There I saw many of the species that typify that zone: black-headed grosbeaks, rufous-sided and green-tailed towhees, lesser goldfinches, rock wrens, lazuli buntings and white-throated swifts, among others. Driving up the Canyon road to U.S. 285, I turned north for a short distance and took the Parmalee Gulch Road to Mt. Falcon Park, which sits at 7800 feet between Turkey Creek and Bear Creek Canyons. This is an excellent area to observe birds of the Transition Zone (Montane) Forest; today was no exception. Among the residents are mountain chickadees, pygmy nuthatches, pine siskins, violet-green swallows, Steller's jays, Townsend's solitaires, western tanagers and both mountain and western bluebirds. The highlight of this stop was a pair of broad-tailed hummingbirds that kept buzzing a loggerhead shrike; perched atop a ponderosa pine, he was apparently too close for their comfort.

Descending to the Bear Creek Valley, I watched a pair of dippers at the Kittredge town park and then headed through Evergreen on Colorado 74. A few miles north of town is the turnoff to Colorado 103, which climbs westward to Echo Lake and Mt. Evans. After passing Elk Meadow, the road winds up through the forest, entering the Subalpine Zone. A large, aspen-lined clearing at 9200 feet is a good place to stop for some birding; this morning I found yellow-rumped warblers, chipping sparrows, mountain chickadees, red crossbills and a pair of pine grosbeaks. Further up, the road skirts the north flank of Squaw and Chief Mountains, providing a spectacular view of the Continental Divide. Picnic areas along this road are always rewarding for birders; gray jays, Clark's nutcrackers and dark-eyed juncos (gray-headed race) were today's primary visitors.

Echo Lake sits at 10,600 feet near the junction with the Mt. Evans toll road. The trees and shrubs around the lake are usually good for Wilson's warblers and Lincoln's sparrows but I took a pass, paid my $10 toll and headed up the highest paved road in the lower 48. At timberline, the Mt. Goliath Bristlecone Pine area is another hotspot for birders; white-crowned sparrows, mountain bluebirds, red crossbills and pine siskins dominated the show today. Another six miles across the scenic tundra (watch for marmots, bighorn sheep and mountain goats) brings you to Summit Lake, tucked in a cirque at 12,830 feet. American pipits are common here and it is one of the best sites in the country to find brown-capped rosy finches (I saw five this morning). Ravens soar along the sheer cliffs, pikas call from the boulder fields and, if you're lucky, you might spot a white-tailed ptarmigan on the flower-laden tundra.

Monday, July 14, 2008

A Natural Inventory

Avid bird watchers are notorious for keeping lists. They compile a life list, a list for the year, day lists and location lists. Such activity is enjoyable, broadens their experience, fulfills their competitive drive and sharpens the skills so important to their hobby.

I recommend that amateur naturalists also develop the habit of keeping lists; an inventory of plants and animals on your property is perhaps the best project. Regardless of the size of your yard, you will soon be amazed by the variety of trees, shrubs, wildflowers, birds, amphibians, reptiles and mammals that populate your inventory. Truly committed participants could include weeds, grasses, fungi, insects and other invertebrates. New species are added over time as they drop by, fly over, wander in or germinate.

The production of this inventory will provide many hours of entertainment, introduce you to new species and increase your awareness of both the diversity and interdependence of life forms that inhabit your personal ecosystem. Hopefully, this will inspire your interest in all of Earth's species and encourage your support for conservation programs across the globe.

Sunday, July 13, 2008

Plates and Continents

Amateur geologists often assume that the continental and oceanic plates coincide with the observable physical geography. In fact, most of the tectonic plates harbor both land and sea areas, which are merely surface features on the thick, underlying plates. For example, there is no Atlantic Plate; rather, this ocean is opening along the mid Atlantic Ridge and the crust formed on either side becomes part of the bordering Continental plates (i.e. this ridge is a rift between the North American and Eurasian Plates and between the South American and African Plates).

Land associated with a particular Continent does not always lie on that Continental Plate. The North American Plate, for example, stretches from the middle of the North Atlantic to the Pacific Coast; however, its northwestern extension runs across the northern edge of the Pacific Ocean, taking in the Aleutians, the Bering Sea, the northern islands of Japan and the eastern portion of Siberia. On the other hand, Southern California lies on the Pacific Plate but will eventually join the North American Plate after a long journey to Alaska. India, part of Asia on the map, actually sits on its own plate and Australia's plate runs beneath most of the Indian Ocean, a swath of the Southern Ocean, the eastern islands of Indonesia and both the Coral and Tasman Seas.

Since most earthquakes and volcanoes are associated with friction, compression and subduction along plate margins, it is important to know where these margins are located. More often than not, they do not correspond with what we see on the map!

The American Antelope

Pronghorns are common across the High Plains, from the western Dakotas to Mexico, and on sage grasslands of the Intermountain West. Natives of North America, they are the sole remaining species of a family that included up to 13 members during the Tertiary Period and Pleistocene Epoch. Most paleontologists believe that pronghorns are not directly related to Old World antelopes and some feel that they are more closely aligned with cattle, sheep and goats. Indeed, like bovids, they have a horn composed of a keratin sheath that overlies a bony core; however, unlike bovids, the pronghorn's sheath is branched (in males) and is shed each year.

Once numbering over 40 million individuals, the pronghorn population declined dramatically throughout the 1800s and early 1900s due to over hunting and the fencing of rangelands. Unable to leap over fences, many starved when they were prevented from migrating during periods of heavy snow. Pronghorns are otherwise well equipped to withstand the harsh winters that typify most of their range; though relatively slender animals, they have a dense undercoat and their outer hairs are hollow, providing superb insulation.

Male pronghorns are territorial from late spring through early fall and gather a harem of up to 20 females; younger males travel about in bachelor herds and occasionally challenge the breeding males, often to their own detriment. Breeding occurs in early autumn and females give birth (usually to twins) in early summer. The young are kept hidden for several weeks and, by then, are able to outrun coyotes, their primary predator; as adults, they will become one of the fastest mammals on Earth, able to reach speeds of 70 miles per hour. In winter, pronghorns congregate in large herds, feeding on the lee side of mesas and roaming about to find open forage.

Saturday, July 12, 2008

Visual Pollution

As the political season gets underway, candidate signs are popping up all over Columbia. Some lawns host four or five candidates while others have several signs for the same individual. Large banners adorn the major intersections and smaller signs are affixed to cars and phone poles. Well-financed candidates smile down from interstate billboards and even scenic, country barns are plastered with names and slogans. To imagine that this visual pollution actually translates into votes is truly disturbing.

Then there's the permanent gauntlet of billboards along I-70. For a State with as much natural beauty as Missouri, the Government seems to be oblivious to these hideous displays. While other States are having them removed, Missouri condones new, monstrous structures that highlight the ads. Given that a significant percentage are rented by Adult Video stores, visitors and travellers may easily misinterpret the State's "Show-Me" nickname.

Conservation efforts should be directed at landscape as well as at habitat, species and natural resources. Though I vote in Colorado, I would gladly campaign for someone who wants to eliminate billboards and political signs in Missouri!

Friday, July 11, 2008

Man and his Animals

Humans have been capturing, breeding and using other animal species since the end of the Pleistocene. Dogs were the first to be domesticated, used for protection and hunting in the Middle East about 12,000 years ago. Goats were raised in the Fertile Crescent 10,000 years ago, followed by pigs and sheep in Turkey-Syria a thousand years later. Cattle were domesticated from northern Africa to India 8000 years ago; cats entered households in Egypt and chickens were first raised in Southeast Asia about the same time.

The horse, so important to the advance of human culture, was first used by humans in central Asia about 6000 years ago, followed by donkeys and camels across northern Africa and the Middle East 500 years later. Ducks were bred in Southeast Asia 5000 years ago, tribes in the Andes domesticated guinea pigs 4500 years ago and turkeys were raised in Mexico by 100 AD.
Europeans domesticated honey bees about 500 AD and rabbits by 1500 AD. Of course, a host of other species have been housed and "trained" in zoos and circuses.

All of this domestication, while often vital to the development of human civilization, has been of benefit to man alone and, as we all know, many animals have endured suffering and abuse along the way. Only our pampered, modern pets, which are engineered and unnatural species, have shared in the benefits.

Thursday, July 10, 2008

Red Rocks Park

Internationally famous for its outdoor, rock-walled amphitheater, Red Rocks Park stretches across the base of Mt. Morrison, just west of Denver. Monoliths of Pennylvanian sandstone (the Fountain Formation) rise above the foothill shrublands, creating a scenic landscape for hikers and naturalists. Just east of the Park, the Dakota Hogback, Cretaceous in age, harbors dinosaur footprints and additional trails.

Foothill grasslands, studded with yucca and juniper, and streamside thickets of Gambel oak and mountain mahogany surround the massive rock formations, attracting a superb variety of wildlife. Golden eagles, common ravens and red-tailed hawks often circle overhead as squadrons of cliff swallows and white-throated swifts swoop along the monoliths. Canyon and rock wrens, rock squirrels, Colorado chipmunks and rock pigeons inhabit the sandstone cliffs and a colorful mix of songbirds nest and feed in the adjacent thickets; among the latter are lazuli buntings, black-headed grosbeaks, rufous-sided and green-tailed towhees, Virginia's warblers, yellow warblers and yellow-breasted chats. Scrub jays, loggerhead shrikes and black-billed magpies noisily patrol the open shrublands, Say's phoebes flycatch from fence posts and herds of mule deer browse the rocky slopes, wary of coyotes and mountain lions that hunt across the foothills.

Red Rocks Park lies west of Colorado 86, between Morrison and I-70 (take Exit 259 from the interstate and head south). A network of roadways and foot trails provide access to this scenic refuge; plan an early morning, weekday visit to avoid crowds and to see an excellent variety of wildlife.

Wednesday, July 9, 2008

The Shade Tree Bird

Northern orioles are common summer birds throughout much of the U.S. Not forest birds, they prefer wood margins and open woodlands with large shade trees and are thus common in older residential areas. Indeed, they once favored the stately American elms that lined our boulevards before elm blight all but eliminated those magnificent trees.

Formerly called Baltimore orioles in the Eastern U.S. and Midwest, this race is now known to interbreed with Bullock's oriole of the West and they have been classified as one species, the northern oriole. Colorful and melodious, these summer residents are known for the pendulous, sack-like nests that they weave from various plant materials; a single brood of 4-6 young are generally raised each summer and family groups may be seen at favored berry shrubs. Adults are otherwise usually found alone or in pairs, scouring trees for caterpillars and beetles.

As one might expect, the Bullock's race, a resident of drier landscapes, is best found in stands of cottonwood that line the rivers and large creeks of the Western U.S. Like their eastern counterpart, they feed on insects and fruit and are frequent visitors to chokecherry shrubs and mulberry trees. Northern orioles generally arrive in the U.S. by early May and depart for Central and South America in mid-late September.

Tuesday, July 8, 2008

Gondwana and Marsupials

Throughout most of the Permian, Earth's land masses had merged into the mega-continent of Pangea. Then, in the Triassic (about 200 million years ago), the Tethys Sea began to form, rifting the northern Continents (Laurasia) from the southern Continents (Gondwana); the latter included South America, Africa, Antarctica and Australia. About 160 million years ago, the northern Atlantic started to open, dividing future North America from Eurasia, and Madagascar broke from Africa, drifting south to join the Antarctica-India land mass.

Marsupials arose in North America during the Cretaceous Period, some 100 million years ago; other mammals had become eutherians (placental mammals) and were beginning to colonize the northern Continents. Just before marsupials spread southward and eastward through Gondwana, the southern Atlantic split Africa from South America and Madagascar rifted from Antarctica, eventually docking off the coast of Africa. About 90 million years ago, India broke from Antarctica, heading toward its collision with southern Asia; South America drifted into isolation 75 million years ago and Australia followed suite 20 million years later.

Marsupials had spread through South America, Antarctica, India and Australia before these latter rifts developed. Those that remained in North America were rapidly displaced by eutherians and, when India merged with Asia, 60 million years ago, the same occurred in that region. South America's marsupials managed to hold on during its prolonged isolation but those in Antarctica succumbed to the climate as that Continent drifted to the South Pole; only those in Australia, free from the competition of eutherians, thrived and diversified. Finally, after Panama lodged between North and South America, some 3 million years ago, the Virginia opossum, our Continent's lone marsupial, spread back from the south.

Monday, July 7, 2008

Recycling and Consumption

Many Americans take part in recycling programs. Every garbage day, they set out their basket of newspapers, soda cans and beer bottles. Yet, despite this important and well-intentioned effort, few take a broader approach to the problem of resource depletion.

Recycling recaptures component materials, reduces the energy needed to produce new items, cuts the space and energy needed for garbage disposal and reduces the destruction and utilization of natural resources. But the recycling step is only part of the solution; we must also be willing to choose products that are made with recycled materials, avoid items whose production threatens natural ecosystems and diminish overall consumption of new products.

Excessive consumption is the primary threat to our natural resources. The demand for new cars, new houses, new clothes and the latest gadgets all take a toll. Of course, this consumption is especially evident in affluent countries, of which the U.S. is king. That basket of recyclables is only a start; we must reduce our population growth and learn to live with less. Otherwise, we will consume our way to desolation.

Sunday, July 6, 2008

The Mammal Explosion

Though mammals first appeared in the Triassic, some 200 million years ago, they lived in the shadow of the dinosaurs and remained rather small and inconspicuous creatures. These therians split into eutherian (placental) and marsupial lines in the Cretaceous (100 million years ago) but did not diversify significantly until the demise of the dinosaurs, 65 million years ago.

Then, over the first two Epochs of the Tertiary (the Paleocene and Eocene), mammals exploded in number and variety. During this period (65 to 38 million years ago), primates, bats, the first ruminants and ancestral elephants appeared. Primates diverged into prosimians (future lemurs, lorises, galagos) and ancestral anthropods (future monkeys, apes, hominids) and, in North America, ancestral horses, rhinos and camels evolved. Canids (wolves, fox, dogs) and felines split from a common ancestor and the earliest cetaceans (whales, dolphins) returned to the sea.

While many of these ancestral species bore little resemblance to modern mammals, the stage was set for mammals to dominate earth's ecosystems. The Cenozoic Era (the Age of Mammals) began with this explosion and continues today. Most assume that humans, which finally graced the scene 125,000 years ago, are the culmination of this process; more likely, we are just another species in the web of mammal evolution.

Saturday, July 5, 2008

Volcanic Islands

While Greenland, Madagascar and Tasmania rifted away from other Continental land masses, the great majority of oceanic islands are volcanic in origin. Of these, most lie along subduction zones, where one of Earth's tectonic plates is subducting beneath another; in these areas, the crust of the subducted plate begins to melt as it approaches the mantle, producing a line of volcanoes on the overlying plate.

The Aleutians and northern islands of Japan have formed where the Pacific Plate is subducting beneath the North American Plate; in like manner, the archipelagos of Indonesia, southeast Asia (Taiwan, the Philippines, southern Japan) and the South Pacific (Solomon Islands, New Zealand) rise above subduction zones at the margins of the Pacific, Australian and Philippine Plates. The Lesser Antilles, stretching along the eastern edge of the Caribbean Sea, were produced by subduction of both the North and South American Plates beneath the Caribbean Plate.

Iceland, which rose from the sea 16 million years ago, has resulted from volcanism along the mid Atlantic Ridge (where the spreading Atlantic continues to rift North America from Eurasia); indeed, this island nation straddles the two Continental Plates. A third type of volcanic island, produced by a mantle plume, can develop far from any plate margin; the Hawaiian Island chain, the Galapagos Islands, the Azores and Easter Island are examples of such isolated "hotspot" volcanism.

Of course, all of these islands are prone to continued volcanic activity, even after hundreds or thousands of years of quiescence; only hotspot islands that have been transported away from the mantle plume (by movement of their oceanic plate) are immune to reawakening. Earth's landscape continues to evolve and humans are finally around to observe it!

Friday, July 4, 2008

Rock Rabbits

Anyone who has been hiking above timberline in the Western mountains has likely heard the loud, high-pitched call of the pika. Resembling a chunky, large-eared hamster, pikas are actually members of the rabbit family; a variety of species are found across the globe and are also known as coneys or rock rabbits.

Favoring rocky slopes and boulder fields, pikas spend much of the day foraging for alpine vegetation which they add to their sheltered haystacks; once the plant material dries out, they take it into their burrows for bedding and nourishment. When not gathering food, these cold-loving mammals perch on boulders to survey and protect their territory. Despite their small size, pikas remain active through the winter, relying on lichen and matted alpine plants if their hay supply runs out.

Usually mating by mid spring, females give birth to 3-4 young after a four-week gestation and nurse them for another month. By then, the young pikas are on their own and, if not killed by golden eagles, hawks, coyotes or weasels, will be full grown by the end of summer. Adult females often raise a second litter after the first group leaves the den.

Thursday, July 3, 2008

Storm Trains

Last evening, a cold front stretched from the Central Plains to southern Michigan, separating warm, humid air, to its south, from cooler and drier air behind the front. Not associated with a potent storm system, the front was relatively stationary, drifting very slowly to the south and east.

Disturbances along the front produced thunderstorms and, as they mushroomed into higher levels of the atmosphere, these storms were nudged eastward by strong, upper level winds that paralleled the front. In concert, another storm would develop at the disturbance; this ongoing process produced linear bands of thunderstorms which, moving eastward, dropped heavy rains across the same locations.

Such "training" can lead to copious rainfall and local flooding. Two to three inches per hour fell in the Greater Kansas City area while parts of lower Michigan received nearly five inches of rain. Meanwhile, wildfires plague the Southwest and parts of the Southeast remain mired in a multi-year drought.

Tuesday, July 1, 2008

Geologic Basins

Novice geologists who visit a region such as the Permian Basin of West Texas might be surprised to find that the area does not resemble a broad valley. Geologic basins refer to the shape of the deep sediment formations and to their deposition in a structural bowl of ancient Precambrian or early Paleozoic bedrock. In the case of the Permian Basin, a thick layer of Permian sea sediments collected within such a basin; now covered over by Mesozoic and Cenozoic strata (which have been sculpted into the West Texas landscape by wind and water erosion) the deeper Permian rocks are tapped for their rich oil and gas deposits.

Further north, the Michigan Basin is often confused with the glacial-carved basin of Lake Michigan (a shallow surface feature). Rather, centered over Lower Michigan, this geologic basin extends from western New York to eastern Wisconsin and from Upper Michigan to northern Ohio. This broad bowl of Precambrian bedrock has gradually filled in with Paleozoic and Mesozoic sediments; as layers were added over a span of 400 million years, the basin closed in from the periphery and the youngest deposits (Jurassic in age) lie in the central part of Lower Michigan. Lakes Michigan, Erie and Huron, the varied topography of Michigan and Niagara Falls are all erosion-produced surface features of the Basin.

In northeastern Wyoming and southeastern Montana, the Powder River Basin is famous for its vast supply of low-sulfur coal. Derived from swamplands of the late Cretaceous and early Tertiary Periods, this coal is near the surface of a wide geologic basin that underlies the region and includes deposition layers that date back to the Precambrian Era. Unlike the other examples discussed above, Powder River is also a topographic basin, a broad valley that has been eroded from the surrounding landscape by the River and its tributaries; indeed, this erosion of soft, overlying Tertiary deposits has made the Powder River coal especially accessible.