Saturday, May 31, 2008

Prairie Crayfish

Most of us associate crayfish with southern bayous, shallow rivers and rocky creeks; some of us also recall the blind, albino crayfish that inhabit the streams and pools of caves. But there are also a large number of terrestrial species, of which the prairie crayfish is one of the more common.

Favoring wet meadows and floodplain grasslands, prairie crayfish dig burrows to access their cool, moist habitat, often leaving chimneys of mud around the entrance. Deep enough to reach the water table, these burrows may be far from surface water and often extend to depths of six feet. The crayfish emerge from the burrows at night (or during periods of cloudy, humid weather), wandering the grassland to find mates or food. In spring and fall, large numbers may be encountered on rainy mornings as they cross trails or country roads.

Terrestrial crayfish can be a nuisance in some crop or tree farm regions but otherwise play an important role in the wetland-prairie ecosystem. Their digging aerates and mixes the soil and their burrows provide wintering sites for amphibians, lizards and snakes. Showing little appreciation, these same creatures feed on the crayfish, as do herons, raccoons, otters, mink, fox and humans. Those that survive predation mate in March and the female crayfish carries fertilized eggs on her abdomen for two months; once hatched, the tiny youngsters remain attached to dear old mom through their first two molts before dropping off to fend for themselves.

Friday, May 30, 2008

Signs of Summer

After a long, cool spring, summer has taken control in mid Missouri. The canopy has closed in, the tulip trees (yellow poplars) are in bloom and the mimosas are leafing out, among the last trees to do so. Flower clusters are forming on the elderberry shrubs, roses adorn the fence lines and tiny walnuts are developing in the new growth of their parent trees.

All of the summer birds have returned, including a pair of great crested flycatchers that have been moving among our shade trees this week. A morning dove is incubating her second brood of the year, the third litter of cottontails are roaming the lawns and the "peents" of common nighthawks echo across the evening sky. And, finally, the toads are trilling from their nocturnal rendezvous sites.

A south wind has carried warm, moist air up from the Gulf of Mexico, providing fuel for thunderstorms later in the day. This mild flow is forecast to continue through the week as summer solidifies its hold on the lower Midwest. Indeed, as evidenced by the movement of severe weather from the southern to the northern Plains, the jet stream is retreating toward its more northern, summer pattern. Our attention will soon shift from tornadoes to hurricanes!

Thursday, May 29, 2008

The Piedmont Puzzle

The Southeast Piedmont is a geophysical province that stretches from the Mid-Atlantic region to central Alabama. This broad swath of rolling terrain separates the Appalachian Mountains, to the west, from the Coastal Plain, to the south and east. For geologists, the formation of the Piedmont has long been a puzzle.

The Piedmont's bedrock is a mosaic of Precambrian and early Paleozoic rocks (1.2 billion to 500 million years old), represented by igneous and metamorphic components. Some of these formations contain rock that is not otherwise found within the North American craton, suggesting that they arrived as exotic terrains; volcanic components, on the other hand, indicate that they likely formed as offshore, island arcs before merging with the edge of the continent. Finally, areas of volcanic Triassic rock, found near the eastern edge of the Piedmont, are remnants of rifting between Africa and North America as Pangea split apart and the Atlantic began to open (almost 200 million years ago).

The many suture lines between the puzzle pieces of the Piedmont underwent some disruption during the rise of the Appalachians (250-300 million years ago), allowing plutons of magma to form within some of the rock layers. Eventually, as the encasing rock was worn away by erosion, these igneous monoliths were revealed; monadnocks, most common near the edge of the Appalachians, and Stone Mountain, near Atlanta, are excellent examples. Deep soil covers the bedrock in most areas of the Piedmont but, at the fall line (where this province abuts the Coastal Plain), the hard basement of the Piedmont is revealed by waterfalls.

Wednesday, May 28, 2008

The Death of Orphans

Earlier this week, my wife and I saw three baby opossums in our yard. They were clearly younger and smaller than those I have seen clinging to the backs of their mothers in the past; newborn opossums generally nurse until they are two months of age and thereafter fend for themselves. Within two days of spotting the babies, I found all three is various stages of dismemberment, likely the victims of cats, owls or raccoons. It seems apparent that they were either abandoned by their mother or, more likely, that she herself was killed.

Premature death is, of course, common in the animal kingdom. Young birds and cottontails are often the victims of snakes, raptors and carnivorous mammals, including domestic cats. Indeed, the very young, the injured and the frail are the usual targets of natural predation, a process that keeps populations in check and maintains the overall health of the species and its ecosystem.

We prefer to focus on the beauty and serenity of nature but, to truly understand her cycles, we must acknowledge the roles that violence, death and decomposition play. Nature is neither fair nor sentimental.

Tuesday, May 27, 2008

An Explosion of Life

After a few days of heavy rain and sultry weather, there has been an explosion of life at the Forum Nature Area, a local wetland-prairie preserve. The greenery is lush, the ponds and lakes are flooded and a variety of wildflowers color the landscape; the latter include yellow coreopsis, wild rose, buttercups and wild irises. The lead plants, typical shrubs of the mesic prairie, are also in bloom, their purple flower stalks attracting hordes of bees.

The bird population continues to grow, with yellow-billed cuckoos making an appearance this week. Other summer residents include green-backed herons, great blue herons, killdeer, spotted sandpipers, eastern kingbirds, gray catbirds, indigo buntings, eastern phoebes, common yellowthroats, eastern bluebirds and the ubiquitous red-winged blackbirds. Clouds of insects offer plentiful prey for tree swallows, barn swallows and chimney swifts while, along the shores, bullfrogs and green frogs have graced the scene, their distinctive calls rising from the wetland.

The highlight of yesterday's visit was a large congregation of northern water snakes, plying the shallows at the west end of the lake. Constantly on the move and showing no signs of stalking prey, they were likely males in search of a receptive female; this is their breeding season and, in fact, the source of their excitement was probably the large adult lounging in a nearby sapling (females are significantly larger than males). If impregnated, she will give birth to anywhere from 12 to 60 live young in late August.

Monday, May 26, 2008

Rio Grande Rift

Ten million years ago, as the Miocene-Pliocene Uplift of the Intermountain West continued, fracture lines developed from southern Colorado to southern New Mexico and a long block of crust stopped rising with the surrounding terrain. Volcanism developed along some margins of the block and at other faults within the rift zone, creating lava flows, producing volcanic mountain ranges and showering the region with eruptive debris. In other areas, fault-block mountains formed, their steep walls facing the rift while their opposite slopes drop gently to the surrounding landscape. In concert with these events, erosion of the rising terrain along the margins of the block spread aprons of sand and gravel across the rift valley.

In southern Colorado, these events created the broad San Luis Valley, flanked by the San Juan and La Garita Mountains to the west and the high spine of the Sangre de Cristos to the east. Further south, the volcanic Jemez Mountains of northern New Mexico rise along the west edge of the rift while the fault-block Sandia and Manzano Ranges tower above its eastern edge, just east of Albuquerque. To the west of that city, a north-south line of volcanic peaks rise above a fault within the rift valley and, in southern New Mexico, volcanic and fault-block ranges mark the borders of the depression.

As noted above, thick layers of volcanic and erosional debris now fill the rift valley; 10,000 feet of this loosely compacted material has produced the flat landscape of the San Luis Valley and Albuquerque sits atop 5000 feet of sediment. The Rio Grande River, rising in the San Juans of southwestern Colorado, flows southward through the heart of the rift, slicing through the valley fill, including a thick lava bed west of Taos.

Sunday, May 25, 2008

A Wedge of Summer

It has been a cool, cloudy, breezy spring in Missouri, with highs often below 70 F and lows near 50. Plants are a good week or two behind schedule and we have yet to experience a summer-like evening. But all will change for the next 48 hours.

The deep trough that has brought unusually cold weather to the West is beginning to shift eastward and lift northward; in other words, the dip in the jet stream is widening and, at the same time, flattening out. The leading edge of the trough is advancing toward the Midwest and Southern Plains as a cold front and, ahead of this front, warm, humid air is streaming northward into the Heartland. A wedge of summer will poke into our region over the next two days, pushing highs into the mid 80s and setting the stage for severe thunderstorms; the low tonight is forecast to remain above 70.

As the cold front continues to advance and flatten out (west to east), we'll return to more seasonal conditions but should stay above the range of our recent Canadian spring. Summer will likely entrench itself by June and we can begin complaining about the heat!

Saturday, May 24, 2008

Polar Bears and Extinction

Polar bears and humans both evolved late in the Pleistocene Ice Age; the bears evolved from terrestrial species about 300,000 years ago while humans appeared in East Africa about 125,000 years ago. Prior to the evolution of these two mammals, millions of other animal species had evolved and become extinct, almost always in association with major upheavals in the climate, sea conditions or terrestrial environment.

Today, polar bears are threatened by a warming climate and, to a lesser degree, so is man. Most scientists believe that human activity is responsible, at least in part, for the accelerated global warming but this is at least the fourth major period of warming since the onset of the Pleistocene, 2 million years ago. And while the planet has undergone numerous cycles of cooling and warming over the past 4.6 billion years, this is the first time that man, with his intelligence and technology, has been around to observe the drama.

There is no doubt that humans have been responsible for decimating animal populations over the years. Over hunting, habitat destruction and pollution have all taken a toll and any efforts that we make toward wilderness protection, pollution reduction, hunting restrictions and human population control will help to sustain the diversity of this planet. Beyond these measures, we and the polar bears are at the mercy of events over which we have little control; whether humans will fare better than the polar bears is yet to be seen and, let's not forget, they have already out-lived us by 175,000 years!

Friday, May 23, 2008

Black Skimmers

Attractive yet comical in appearance, the black skimmer is one of our more interesting coastal birds. Identified by its black and white plumage, red feet and black-tipped, red bill, it is the only bird with a lower mandible that is longer than its upper bill. Resting on the beach, the skimmer cuts a low profile, with its long beak, short legs and long wings; in flight, its wing span is more than twice the length of its body.

Favoring remote, sandy beaches, black skimmers breed along the Atlantic and Gulf Coasts, from southern New England to the northern shores of South America; on the Pacific Coast, they are found from southern California to South America. Gregarious, they breed in large colonies, often in the company of of least terns, choosing flat beaches with little or no vegetation. Nesting occurs from late May through early July and three to five eggs are laid in a shallow depression, directly on the sand. Chicks are born with even mandibles, allowing them to pick food from the surface of the beach.

Adults are graceful and buoyant fliers, often moving about in synchronized flocks. When feeding, they are usually found alone or in small groups, skimming the surface with their lower mandible and then snapping the bill shut when they encounter prey; they prefer to feed on calm, coastal bays but may hunt along the shoreline if wave action is limited. Come autumn, the black skimmers of New England migrate to the south, wintering along the Southeastern and Gulf Coasts.

Thursday, May 22, 2008

Yellowwood Trees

In central Missouri, flowers color the landscape from late winter through mid fall, even later in some years. But the peak of fragrance occurs in May, when lilacs, black locust and yellowwoods bloom (generally in that order). The latter is a small tree native to the mid Mississippi Valley, favoring the lime soils of Kentucky, Missouri and Tennessee; it is otherwise widely planted as an ornamental.

The yellowwood tree is the only member of its genus but is grouped with other legumes: acacias, locusts, redbuds, paloverde, mesquite and mimosa. Growing to sixty feet, they branch low on the central trunk and their oval, compound leaves resemble those of ash trees; come autumn, these leaves turn a bright yellow. The fragrant, white flowers hang in clusters, appearing in late May or early June.

Yellowwoods are named for the color of their freshly cut wood, which browns with age and is among the hardest of North American trees. Long used for firewood and for the construction of tools and rifle stocks, the wood of this tree has also been used to produce a clear, yellow dye. Here in Columbia, yellowwoods have been planted across the University of Missouri campus, providing a beautiful and fragrant display in spring and a brilliant glow in fall.

Wednesday, May 21, 2008


Located in southeast Missouri and spreading across the abandoned channel of the Mississippi River, Mingo National Wildlife Refuge covers almost 22,000 acres of wetlands, bordered by the Ozark Uplift on the west and Crowley's Ridge on the east. This refuge, established to protect habitat for migrant and wintering waterfowl, is well known to naturalists for its excellent diversity of flora and fauna.

A Visitor Center, off Route 51 north of Puxico, Missouri, introduces visitors to the natural and human history of the area and to the many species that inhabit this vast preserve. Those who arrive in April-May or October-November can follow a 20-mile auto tour road (open 8am-4pm) which leads through the varied habitats of the refuge. Spring visitors should see a wide variety of wetland birds, including herons, egrets, rails, bitterns, Mississippi kites, wood ducks, hooded mergansers, barred owls, common yellowthroats and prothonotary warblers; wild turkey, barn owls and pileated woodpeckers are among the upland species. Resident mammals include river otters, mink, muskrat, beaver, red fox, bobcats and white-tailed deer.

Bald eagles nest along Monopoly Lake, which also attracts ospreys during the spring and fall migrations. Mingo is also known for rare summer visitors, including anhingas, roseate spoonbills and fulvous whistling ducks. Autumn brings huge flocks of wintering waterfowl to the refuge; among these travellers are tundra swans, trumpeter swans and snow geese.

Tuesday, May 20, 2008

The Great Equalizers

The recent natural disasters in Myanmar and China highlight the devastation that such events can bring. And, despite the political and bureaucratic roadblocks, they have, once again, demonstrated an outpouring of global support that occurs in all of these situations.

Natural catastrophes, monstrous, unpredictable and unpreventable, are especially unsettling to the human psyche. Though they have often struck "developing countries" in the recent past, we all know that many of our modernized, populous regions are also prone to these events, whether they be earthquakes, tsunamis, hurricanes, volcanic eruptions, wildfires or massive storms. Though we can mitigate their effects to some degree, we are essentially helpless in the face of nature's most powerful forces. And, when we eventually face a global crisis, triggered by an asteroid strike or other devastating event, the survival of our species will depend upon a degree of cooperation that will make artificial human boundaries insignificant.

Major natural disasters are humbling events and remind us that wealth, power and prestige cannot protect us from their wrath. They are the great equalizers on this planet.

Monday, May 19, 2008

Craziness at Dark

It began about 10 PM last evening. A mix of hissing, piercing cries and hysterical hoots rose from the backyard. Initially thinking that it may be a cat fight, I went to the back door but, without a working flashlight (don't tell Jim Cantore), I couldn't see a thing. Then, the riotous outburst gave way to the distinct call of the barred owl and I knew from what the craziness arose.

Barred owls favor wooded swamplands and ravines and I often hear them calling from a creekside forest down the road. Preferring seclusion during the day, they hunt for mice, birds and small cottontails at night and may turn up in residential areas. Their call, an eight hoot sequence (often described as "who cooks for you, who cooks for you-all?") is higher pitched than the deep hoots of the great horned owl and may be preceded by the cacophony described above.

These dark-eyed owls generally nest in late winter and their downy young (usually 2 to 4) hatch by late March. Last night's visitor may have been a mother, hunting for its brood, or just a lone adult, out to stir up the neighborhood!

Sunday, May 18, 2008

Dinosaurs and the Grand Canyon

Mention geologic history and most people think of dinosaurs or famous landforms, especially the Grand Canyon. No doubt, many visitors have stood at the rim of that magnificent chasm and wondered about all of the dinosaur fossils that it might contain. But is the Grand Canyon older or younger than the Age of Dinosaurs? The answer is both.

The rock layers of the Grand Canyon represent an historical record that stretches from the middle of the Precambrian Era (almost 2 billion years ago) through the Paleozoic Era, which ended 225 million years ago. The oldest rocks are at the base of the Canyon while the youngest (Permian sandstone) forms its rim. On the other hand, this layer cake of geologic history has been revealed by the erosive force of the Colorado River and by freeze-thaw erosion along its walls; all of this erosive activity has occurred very "recently," within the past six million years.

The dinosaurs lived during the Mesozoic Era, which began 225 million years ago and ended 65 million years ago. Fossils of these fascinating creatures are thus found in rocks that formed from mud, sand or volcanic deposits of that Era and thus would not be found in the rocks that line the Grand Canyon; the dinosaurs lived after the rocks of the Canyon were deposited but well before the Canyon formed! The only potential source for dinosaur fossils in the Grand Canyon would be via the Colorado River, which, along with its major tributaries, erodes the Mesozoic strata of the Colorado Plateau, to the north and east (an unlikely event that is now virtually impossible due to the Glen Canyon Dam).

Too often, students of natural history forget that life evolved in concert with a changing landscape. The timing of evolutionary events determines where we expect to find fossils of a particular life form and, conversely, the presence of fossils in rock of a known age helps us understand the ecology of that specific period.

Saturday, May 17, 2008

Last Day on the Farm

It's the last day on our Littleton, Colorado, farm before returning to Missouri, where my real job awaits. Despite some rainy weather (always welcome out here), it's been a good week, with a mix of chores and recreation. Summer-like conditions returned today, with a high near eighty, but the greenery and color should last for another month or so.

The wet, mild spring produced a spectacular lilac bloom this year and the chokecherry blossoms are more extensive than I've seen in years, a good omen for the birds and squirrels that feed on their fruit. The mulberries are just beginning to form and, until they're ripe, there's plenty of juniper berries for the robins, catbirds and waxwings. Western tanagers stopped by this week, an annual visit on their way to the mountains; other migrants have included yellow-rumped warblers, white-crowned sparrows and ruby-crowned kinglets. Two of our summer residents, northern orioles and broad-tailed hummingbirds, also returned this week.

Unfortunately, we seemed to have lost our resident pair of red fox; I've seen neither the red female nor her melanistic partner this visit and we usually have pups roaming the farm by now. Recent work on our pasture fence may have scared them off or, perhaps, one of the adults has been killed. We, of course, have an open door policy for all wildlife and, if we're lucky, the fox will return for our visit in June.

Friday, May 16, 2008

A Walk in Waterton

Waterton Canyon, the South Platte's final slice through the Rockies, is an excellent destination for a nature walk in any season; however, due to large weekend crowds, I recommend a weekday morning visit. Wildlife is usually abundant and the rugged cliffs of Precambrian granite offer a scenic background at every turn.

Today dawned cloudy and cool but the Canyon was clearly in its spring mode and most of the summer residents had returned. Rufous-sided towhees, yellow warblers and gray catbirds dominated the scene but broad-tailed hummingbirds, violet-green swallows, yellow-breasted chats, lesser goldfinches and western tanagers were all back from the south. As usual, great blue herons, mallards and the ubiquitous Canada geese fed along the river, joined by belted kingfishers, spotted sandpipers and a few American dippers; despite the presence of large lakes just downstream, double-crested cormorants have also begun to fish here in recent years. This morning, I encountered two pair of common mergansers, lounging on boulders in the turbulent stream, apparently foregoing a migration to Canadian waters.

Despite a large variety of summer birds, some permanent residents were less common than usual this morning; only a few scrub jays, canyon wrens and magpies graced the Canyon and, for the first time in years, I failed to see a golden eagle. In addition, the mammal population must have been sleeping in; only a few mule deer browsed the slopes and I saw only one small group of bighorns, resting in a side canyon. But that's the beauty of nature hikes: on any given day, your expectations may be dashed or exceeded, often at the same time!

Thursday, May 15, 2008

Air Show

Yesterday, warm sunny weather provided a good opportunity to remove winter's debris from our Littleton farm and prepare the trees and shrubs for the hot, dry months ahead. No sooner had I reached the mulch pile than two jet fighters streaked across the southern sky, curved over the foothills and retreated to the east, leaving a thunderous roar in their wake. While I watched their departure, another squadron flew just above the treetops, heading north; this group, a flock of double-crested cormorants, was much quieter and somehow more reassuring.

Taking a break by mid morning, I caught sight of a dozen American white pelicans, circling their way northward above the South Platte Valley. An hour later, nervous calls from the squirrels and songbirds drew my attention to a pair of Cooper's hawks that were hunting their way through the neighborhood. But the highlight of this air show was a large Swainson's hawk that circled above the farm for a few minutes and then stooped at high speed toward one of our pastures; apparently missing his target, the handsome raptor perched in the top of an elm, surveyed the scene for ten minutes or so and then moved on.

The morning show reminded me of a childhood experience more than fifty years ago. Playing in my grandfather's yard, I was called over to his lounge chair and asked if I saw any birds. Looking around, I said that none were present; my grandfather laughed and pointed out a large flock of chimney swifts that were feeding high overhead. "Always remember to look up or you just might miss something," he said. Wise words from my first mentor!

Wednesday, May 14, 2008

Spring on the Front Range

Most Americans who have never lived in Colorado likely picture the Front Range urban corridor as a winter wonderland for nine months of the year. After all, Denver and its cohort of cities are the gateway to the Rockies and most Colorado ski vacations pass through this portal. But while the higher mountains can be cold and snowy for much of the year, the Front Range cities enjoy a mild, sunny climate, even in the midst of winter.

Winter snows generally average no more than 4-8 inches and quickly melt due to the dry air, intense sunshine and Chinook winds. Periods of mild weather, with highs in the sixties, are not uncommon at any time of the year; on the other hand, the high elevation and thin air usually produce overnight lows in the teens (winter) to low fifties (summer). This warm, sunny climate makes the Front Range an appealing place to live and encourages outdoor activity throughout the year. Then there's spring!

The downside, if there is one, of the Front Range climate is the fickle spring weather with its famous upslope snowstorms. Indeed, most of Denver's annual snowfall arrives in the months of March and April and heavy, wet snows may occur into May. These bouts of winter, interspersed with periods of mild, sunny weather, can be especially frustrating for gardeners; just as their spring flowers are bringing color to the yard, they are crushed by a foot of snow. And though melting is rapid, the damage to leaf-bearing trees can be extensive. Spring in Colorado: an annual headache for some, a minor inconvenience for those of us who love this climate.

Tuesday, May 13, 2008

Driving Through the Seasons

Anyone who has traveled I-70 between Missouri and Denver knows that it is not the most interesting trip in this magnificent country. While the rolling farmlands of Missouri, the Flint Hills of eastern Kansas and the Palmer divide region of eastern Colorado provide some scenic relief, most of the route crosses relatively flat landscape. The weather, on the other hand, is another story.

Leaving Columbia yesterday morning, the sky was clear and bright, the thermometer sat at 42 degrees F and a gentle east breeze made it feel like October. Heavy dew covered the ground and, just west of Columbia, a dense fog shrouded the Missouri River floodplain, pierced by squadrons of cliff swallows that fed near the bridge. Further west, in eastern Kansas, the temperature was in the low sixties, cattle grazed on the green carpet of the Flint Hills and a pair of scissor-tailed flycatchers lounged on a wire fence, soaking in this mid spring day. Sixty miles further, in central Kansas, a stiff south breeze developed, whirling the giant turbines of the wind farm north of Ellsworth, and pushing the thermometer into the seventies.

By the time I reached the High Plains of the Kansas-Colorado border, the wind had shifted to the southwest and the temperature had soared into the upper 80s; needless to say, it felt like a mid summer day when I stopped for gas in Burlington. Yet, dark clouds to the northwest warned of another change down the road and, as I crossed the Palmer Divide north of Limon, northeast winds were producing a thick cloud layer along the Front Range. This upslope flow dropped the temperature into the forties by late evening and produced a mix of rain and snow overnight. Nothing like the experience of four seasons in one day!

Sunday, May 11, 2008

Motherhood and Abortion

As we all know, not all pregnancies are planned. And, conversely, desired pregnancies are not always achieved. Animal studies have demonstrated that almost half of fertilized eggs fail to implant in the uterus; of those that do implant, some are lost to spontaneous abortion (miscarriage). The "pro-life" contingent, which insists that life begins at fertilization, are either ignorant of these facts or choose to ignore them.

Furthermore, anti-abortionists, some of whom even oppose the procedure in cases of rape, incest or maternal risk, see adoption as the answer, pointing out that abortion leaves the mother with emotional scars. Labeling the pro-choice position as "pro-abortion," they seek to impose their view on the rest of society. Few of these individuals have adopted unwanted or abused children and most seem to ignore the emotional problems faced by mothers who give up full term babies or by the adopted children themselves. To compound the issue, one of the leading opponents of abortion, the Catholic Church, also opposes the use of birth control, the primary means (other than abstinence) of preventing unwanted pregnancies.

On this Mother's Day, let's acknowledge that we hope all children are wanted, loved and raised with care. And, contrary to the rhetoric of the Religious Right, let's agree that no one wants to have an abortion. Unfortunately, anti-abortionists prefer the birth of an unwanted child to the elimination of a fertilized egg and, in this political year, their self-righteous demands will blur the concept of motherhood.

Saturday, May 10, 2008

The Hair Bird

Most Midwestern sparrows are permanent or winter residents. Among "summer sparrows," the small, slender chipping sparrow is perhaps the most common. Favoring wooded meadows and woodland borders, this handsome bird is also fairly common in urban parks and residential areas. Easily identified by its bright chestnut crown, prominent white eyebrow, black eye line and gray nape patch, the adult chipping sparrow also has two white wing bars and a long, notched tail.

In the past, chipping sparrows were known as "hair birds" due to their habit of lining their nests with horse hair; they still use animal hair in rural areas but have otherwise adapted to the industrial age by using fine plant materials. Summering across southern Canada and through most of the lower forty-eight, they feed on seeds and insects, typically foraging on the ground and flying into nearby trees as you approach. Migrants are most often seen in residential areas during mid spring (late April to early May) and again in early October; wintering grounds are along coastal areas of the southern U.S. and in Mexico.

Friday, May 9, 2008

Paleozoic Life

When the Paleozoic Era dawned, 600 million years ago (MYA), the Earth was already four billion years old and life had existed in the primordial sea for three billion years. Shelled marine life had evolved but, through the first period of the Paleozoic, the Cambrian (600-500 MYA), these creatures exploded in number and variety; among them were the trilobites, which survived throughout the Era. The Ordovician Period (500-440 MYA) witnessed the appearance of bryozoans, conodonts (the earliest vertebrates) and jawless fish. During the Silurian (440-400 MYA), vascular plants, ammonites, freshwater fish and jawed fish (spiny fish and placoderms) evolved; it was in the Silurian that plants and animals first colonized the land.

The Devonian Period (400-350 MYA) marked the appearance of many life forms that persist today; among these were sharks, bony fish, lungfish, primitive amphibians, ferns, primitive arachnids, wingless terrestrial insects and the first tree-like plants. Web-spinning spiders and flying insects first evolved during the Mississippian Period (350-310 MYA), followed by horseshoe crabs and primitive reptiles during the Pennsylvanian Period (310-270 MYA); these two Paleozoic divisions are often referred to as the Carboniferous Period, the peak of coal forest habitat. The final Period of the Paleozoic Era was the Permian (270-225 MYA), during which frogs, lizards, pelycosaurs (mammal-like reptiles), modern reef corals and modern conifers appeared.

This cascade of Paleozoic evolution set the stage for the Mesozoic Era, the Age of Dinosaurs, during which mammals, flowering plants, birds, social bees and snakes also made their debut. But that's the subject for a future blog.

Wednesday, May 7, 2008


In this verdant month of May, a diverse assembly of trees, shrubs, vines, flowers and grasses carpet the landscape. Since our species evolved well after land plants graced the Earth, this sea of green has become part of the collective human consciousness, an environment that we take for granted.

But back in the early Silurian Period, some 440 million years ago, all plant and animal life was limited to the sea, dependent upon the primordial ocean for water, nutrition and protection from the destructive effect of ultraviolet radiation. With the development of the protective ozone layer (high in the atmosphere), marine plants and animals were free to inhabit shallow, coastal regions; nevertheless, lacking transport tubules, plants remained dependent upon an aquatic environment to secure the water and nutrients that they needed.

Then, by the middle of the Silurian (about 420 million years ago) vascular plants evolved, equipped with stems. Able to grow across coastal rocks and beaches while maintaining a foothold in the sea, these pioneer plants eventually developed root systems that eliminated their dependence on the ocean waters and allowed them to colonize the land. Four hundred million years later, they have diversified into an amazing variety of terrestrial plants, from mosses to redwoods. And, of course, the evolution of land plants allowed animals to follow, setting the stage for the rise of amphibians, terrestrial insects, reptiles, dinosaurs, birds and mammals.

Tuesday, May 6, 2008

More Like May

After a sluggish start, it's beginning to look and feel more like May. The canopy is closing in, lilacs and honeysuckle are in bloom and the lawn mowers are getting a workout. Down at the local wetland, cricket frogs are calling, a few green frogs have appeared and green-backed herons have joined their great blue cousins; indigo buntings, eastern kingbirds and common yellowthroats have also settled in for the summer.

Back in the neighborhood, the black walnuts are heavy with staminate catkins, house wrens are singing and a host of birds (robins, mourning doves, cardinals, blue jays) are already raising their first broods of the year. While migrant warblers have been spotty this year, Swainson's thrushes, rose-breasted grosbeaks and white-crowned sparrows have stopped to feed in the yard over the past few days; ruby-throated hummingbirds (already late) and common nighthawks should make an appearance this week. Down the street, the season's first tent caterpillars (the offspring of a moth) have established webs in our neighbor's crab apple trees.

As another Pacific front promises thunderstorms tonight and tomorrow, it appears that winter has finally thrown in the towel. Balmy nights are ahead, bringing an explosion of insects and a feast for the toads; they should be trilling any day now.

Sunday, May 4, 2008

From Southern Cal to Alaska

Much of western North America is composed of land segments that were welded to the primary craton as the Atlantic opened and the Farallon oceanic plate was forced to subduct beneath the Continent as it advanced westward; these segments arrived as volcanic island arcs, created by the subduction itself, or as exotic terranes that were carried in by the oceanic plate. Remnants of the Farallon Plate are still subducting in the Pacific Northwest and along the west coast of Central and South America but the North American and Pacific Plates are now in contact across Southern California; in fact, this segment of the State, from San Francisco to San Diego arrived as an exotic terrane atop the Pacific Plate late in the Tertiary Period. Other than Hawaii, this is the only segment of the U.S. that does not lie on the North American Plate.

The east boundary of this Salinas Terrane (and thus of the Pacific Plate) is the famous San Andreas Fault. About five million years ago, as the East Pacific Rise developed, rifting the Baja Peninsula from Mexico, the Pacific Plate was forced to inch northwestward along the west margin of the North American Plate. Where the fault curves westward, north of the Los Angeles Basin, increasing pressure within the Salinas Terrane forced up the Transverse Ranges and this area of resistance remains a potent source of major earthquakes. Nevertheless, the Plate motion continues, averaging 35 mm per year but occurring as intermittent, quake inducing slips.

Over time, the Salinas Terrane will break free of its contact with North America and ride to the northwest atop the Pacific Plate. Destined to be an island for 20 million years or more, it will eventually merge with the Aleutian Chain of Alaska as its transporting plate dives into the Aleutian Trench. Enjoy the sunny, warm climate while you can!

Saturday, May 3, 2008

A Reluctant Spring

Patience is being tested across the American Midwest as spring is dragging its feet this year. Heavy snows in the north and cold rains in the south make it feel more like March than early May. Here in mid Missouri, the foliage is a good week behind schedule and nights below forty are still a regular occurrence; I have yet to hear the trilling of toads and have no doubt that the swifts and swallows have had some difficult days.

Of course, this streak is well within the "normal" historical range and is purely a regional aberration. The Southwest has been unusually dry and hot this spring and the Southeast is as warm and humid as ever. And though Midwesterners have put their worries about global warming on hold, the hot, sticky weather will arrive soon enough.

We humans are an impatient lot and often have difficulty taking the long view. Wildlife, on the other hand, having no records to check or forecasts to fear, take the days and the weather as they come. White-throated sparrows, unfazed by the cool spring, departed for Canada last week and their cousins, the white-crowned sparrows, are making their annual, early May visit to our neighborhood, moving north before the real heat arrives.

Friday, May 2, 2008

Reno's Quakes

Fifteen million years ago, during the Miocene Period, an uplift of the Intermountain West began. This geologic process continued into the Pliocene, adding up to 5000 feet of elevation to the landscape and producing east to west tension on the crust of the Great Basin. This tugging, which accelerated with the rise of the Sierra Nevada batholith, has thinned and fractured the crust, leading to the development of north to south fault lines throughout the Basin. Indeed, most of the Great Basin ranges are "fault block" uplifts, with a steep edge adjacent to the fault and a more gentle slope on the opposite side of the range.

The rise of the Sierra batholith and the stretching of the Great Basin continues today and, as one might expect, earthquakes are common throughout the region. Many of these are triggered deep in the crust and are barely noticeable at the surface; others, like those in Reno this past week, are closer to the surface and can produce significant damage. While the Great Basin quakes are not likely to be as powerful as those along plate margins (e.g. the San Andreas Fault), they could be catastrophic in populated areas.

Whether Reno, sitting near the eastern edge of the Sierra uplift, has endured the worst of this round is hard to predict. But it is safe to say that there will be plenty more regional earthquakes in the decades and centuries to come. Taking the long view, this rifting process will eventually split the Continent, the ocean will reclaim the Basin and the desert peaks will form islands in a vast, inland sea.

Thursday, May 1, 2008

Tiny Visitors

Several ruby-crowned kinglets have been flitting through our woodland border for the past few days. These tiny birds, with an olive-gray back, white wing bars and white eye ring, feed in the manner of warblers, snaring insects and pupae from shrubs and tree limbs. Their short tail and short, thin bill give them a chunky appearance and they are easily identified by their habit of fluttering their wings; the red crown feathers of the male, usually hidden, are primarily revealed during courtship or territorial displays. Despite their small stature, the song of this common migrant is loud and melodious.

Red-crowned kinglets summer and breed across Canada, northern New England and the mountains of the West. Their migration usually peaks in April and October, during which they are frequently seen in residential areas. Unlike their cousin, the golden-crowned kinglet, which winters throughout most of the U.S., this insectivore spends the colder months in the southern half of our country.