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Showing posts from March, 2015

Grasshoppers in March

We generally associate the presence of Orthopterans (grasshoppers, crickets, katydids) with hot summer days and balmy August nights.  However, some species may be encountered in early spring, especially during periods of warm weather.

Following a week of summer-like conditions along the Colorado Front Range, small grasshoppers are abundant on our Littleton farm.  While most species overwinter as eggs and do not emerge until late spring or early summer, some species winter as nymphs, one of several intermediate stages between the egg and adult forms.  Unlike many insects, Orthopterans mature through incomplete metamorphosis; during the nymph stages they have the appearance of miniature adults and molt as they grow.

Grasshoppers encountered in early spring are those species that winter as nymphs, sheltered from the cold in leaf litter or other plant debris.  Fortunately, these species, while providing an important source of food for a variety of birds and mammals, do not damage cultivat…

First Swallows

Tree swallows spend the winter along the Gulf Coast, across Florida or in Mexico, much farther north than their cousins (barn, cliff, bank, violet-green and rough-winged swallows).  As a result, they arrive on their summer breeding grounds much earlier, generally by mid-late March.

Yesterday, I observed a small flock of tree swallows at South Platte Park in Littleton, Colorado, the first I have seen this season.  Strafing clouds of midges that hovered above the ponds, the swallows had likely hitched a ride on recent southerly winds that brought summer-like weather to the Front Range.  Soon they will pair off and locate a cavity (in a tree or nest box) in which the female will build a nest of dried vegetation.

Arriving in Colorado well before the end of our snow and ice season, tree swallows risk annihilation of their primary food source.  Fortunately, these aerial insectivores can expand their diet to include other invertebrates or plant material if necessary.  Nevertheless, one must …

Mental Illness & Public Safety

This week's air tragedy in France was apparently the result of an unrecognized or unreported mental illness in one of the pilots; that failure led to the death of the afflicted individual and 149 other passengers and crew members.  While the perpetrator had sought medical attention for his condition, its ramifications were clearly not dealt with in an open, thoughtful and honest manner; initial reports suggest that airline executives were unaware of his diagnosis.

Similar tragic episodes have occurred in the military, in other industries and in society as a whole.  Due to our inability to accept the nature of mental illness, on a par with heart disease, diabetes and other human maladies, we are less willing to openly discuss its varied presentations or report our observations to mental health professionals.  We don't want to stigmatize relatives or friends with such a diagnosis and suspect that it might jeopardize their career;  unfortunately, this fear is too often confirmed …

Reading Outside

I often read outside, especially on calm, mild, sunny days.  Sometimes I take a nature magazine or a medical journal but it's usually the latest novel or collection of short stories recommended by my wife or a friend.  However, though my intentions are sincere, I generally end up behaving like an unfocused schoolboy, easily distracted by the natural surroundings.

Yesterday afternoon, I made it through two short chapters before a Townsend's solitaire began calling from the top of a juniper.  Then it was a spotted towhee scratching beneath the pinyon pines and the noisy flocks of Canada geese that circled overhead.  Setting my book aside, I got up to ramble through the farm,  taking notice of the early spring color provided by wild cherry shrubs, dandelions, grape hyacinths, periwinkle, clumps of blue scilla and the expanding greenery itself.  Cottontails darted across the pastures, robins hunted worms and insects on our patches of "lawn," the Mesozoic form a a great b…

A Brief Intense Upslope

After a warm, sunny week, yesterday dawned cool and cloudy along the Colorado Front Range; periods of light drizzle moistened the pavement and the temperature hovered in the mid thirties (F).

Then, about 10 AM, flurries appeared in the air and, within15 minutes, intense snowfall enveloped our farm; two inches fell over the next 90 minutes, coating the trees, shrubs and grass but melting on the warm pavement.  By noon, the show was over and patches of blue appeared in the overcast.

Such brief periods of intense snow are not unusual along the Front Range urban corridor, especially in March and April.  As an unruly jet stream steers cold fronts down from the northwest, northeast winds just behind the front shove moisture from the Great Plains toward the Continental Divide.  Rising with the landscape, the air cools and condensation occurs, often producing bands of intense snow comparable to lake effect snows of the Great Lakes region; as the cold front moves off to the east, the upslope b…

Our Fickle Bushtits

The bird population on our Littleton, Colorado, farm is typical of other properties in the Temperate Zone of Western North America.  We host permanent residents, summer and winter residents, seasonal migrants and intermittent visitors such as Canada geese and cedar waxwings.  But one species is especially fickle, inhabiting the farm for extended periods of time and then disappearing for weeks or even months.

Common bushtits are small, long-tailed, highly social insectivores of the Western U.S. which prefer wooded scrublands, pinyon pine woodlands and suburban parks; they have cousins in Eurasia but are the only member of their family in North America. Twittering as they comb trees and shrubs for active or hibernating insects and spiders, bushtits often forage with chickadees and nuthatches.  Should one pair build their sock-like nest and deposit eggs, the entire flock joins in the incubation process, huddling together through the chilly western nights.

The flocks on our farm vary from…

The Sixth Mass Extinction

Those who study the natural history of our planet have identified five mass extinctions since the dawn of the Paleozoic Era (see Earth's Mass Extinctions).  Worldwide fossil records confirm these events, all of which reset the structure of life's evolutionary tree.

More controversial is the conviction of many biologists that we have entered the Sixth Mass Extinction on Planet Earth, one triggered by the activities of humans.  While life has colonized our planet for 3.6 billion years, humans (Homo sapiens) have roamed its surface for less than 140,000 years; for almost half that time, our species was confined to the African Continent and, for more than 95% of our history, we had little impact on the natural ecosystems of Earth.

Within the last 10,000 years, however, urbanization, cultivation, domestication, exploration and industrialization have had dramatic effects on our home planet and on the other life forms that inhabit its varied marine and terrestrial landscapes.  Spurre…

Cabbage Whites

Looking across our Littleton, Colorado, farm yesterday afternoon, a dozen or more cabbage whites fluttered amidst the greening landscape.  Generally the first butterflies to appear each spring and among the last to be seen in autumn, these small butterflies may be observed as early as February if warm spells envelop the Front Range.

Cabbage whites are off-white to pale yellow in color and bear black spots on their wings; females have two spots while males have one.  Emerging from cocoons in spring, the adults soon mate and females lay eggs on plants of the mustard family (including wild mustard, cabbage and radishes); the eggs hatch to release voracious caterpillars which later pupate to yield the next generation of adults.  In addition to their parenthood role, adults feed on nectar and pollinate a wide variety of wildflowers.

Natives of the Old World (Eurasia and Africa), cabbage whites were introduced in Quebec, Canada, in the late 19th Century and have since spread across most of …

The Casiquiare Connection

We humans have long dug canals to connect watersheds, thereby improving irrigation or shortening navigation routes.  Examples range from small regional projects to the construction of massive channels that require locks and dams to permit river transport.

While natural connections between watersheds are relatively rare, the Casiquiare Canal in southern Venezuela offers a spectacular example.  Bifurcating from the Upper Orinoco River, this waterway snakes southwestward for over 140 miles, dropping 100 feet en route; at its southern end, the canal enters the Rio Negro River, a major tributary of the Amazon.  In effect, the Casiquiare Canal shunts water between two major watersheds, the largest river known to do so on Planet Earth.

How did this river come to cross a natural divide?  It appears likely that the Casiquiare, initially an upper tributary of the Rio Negro, cut its way upstream, eventually capturing flow from the Orinoco.  While the initial connection may have been rather meage…

Duck Count Doldrums

Despite the warm, sunny weather (or perhaps because of it) the March waterfowl count at South Platte Park was rather dull this morning.  The recent summer-like conditions have totally opened the ponds, lakes and wetlands throughout the Valley and the ducks (migrants, winter visitors and permanent residents) are widely dispersed.

Our group saw a fair number of common goldeneyes, buffleheads, mallards, shovelers, gadwall and coot; a few common and hooded mergansers were also observed.  As usual, Canada geese were common on the refuge though their massive wintering flocks have moved off to the north.  A lone double-crested cormorant was seen but no grebes or white pelicans made an appearance.

Migrants should pick up in the coming weeks and summer residents (including pelicans, western grebes, cinnamon and blue-winged teal) generally arrive by mid April.  The summer-like weather, on the other hand, will surely not last; upslope snowstorms are especially common in March and April along the…

The Nature of Fjords

Fjords are steep-walled, U-shaped, glacial-carved coastal valleys.  Especially common along the rocky coasts of Norway, Iceland, Greenland, Canada, Alaska and Russia, they are also found in New Zealand and southernmost South America.  Eroded by mountain glaciers as they flowed toward the sea, the cliff-lined channels now admit ocean waters; since sea levels were much lower during the Pleistocene, the floor of many fjords is hundreds if not thousands of feet below the water surface (and generally deepest inland).  Furthermore, since the glacial tongues left terminal moraines beyond the rocky headlands, those underwater ridges now produce upwelling and strong currents near the mouth of many fjords.

Among the more famous fjords is Sognefjord, in southwestern Norway.  More than 125 miles long and over 4200 feet deep, this scenic, branching channel is the longest fjord in Europe and is second only to Greenland's Scoresby Sund in depth; its majestic cliffs rise 3300 feet above the water…

Two Seasons in One

Over the past few years, especially during the past two winters, weather conditions have been dramatically different in western and eastern regions of North America.  While California endured another warm, dry winter and southeastern Alaska received very little snow, the American Midwest was raked by frigid Canadian fronts and New England was buried by record-breaking snowfalls.

More than an inconvenience for humans and fodder for cable news programs, this stagnant weather pattern (an atmospheric ridge in the west and an atmospheric trough in the east) has caused significant ecological impacts.  A severe, four-year drought persists in the California, threatening water supplies and fueling massive wildfires.  Warm waters along the West Coast have diminished food supplies for many predators, altering their migrations and hunting patterns; stranded by parents who must feed well offshore, young sea lions have turned up on the beaches of California, exhausted, hypothermic and malnourished.…

Zealandia

Zealandia is a long, relatively narrow fragment of continental crust that split from Antarctica early in the Cretaceous Period (about 120 million years ago) and from Australia toward the end of the Cretaceous (about 80 million years ago as the Tasman Sea opened).  This continent, 93% of which is submerged beneath the sea, has since drifted northeastward and now stretches NW to SE, from the tropics, north of New Caledonia, to the sub-Arctic zone, southeast of New Zealand; while most of Zealandia is hidden by ocean waters, it covers an area half the size of Australia.

Northern Zealandia, which is composed of two parallel ridges separated by a long, narrow graben, lies on the Australian Plate while Southern Zealandia (from New Zealand's southern island southward) lies on the Pacific Plate; compression between these plates forced up the Alps on New Zealand's southern island and subduction of the Pacific Plate beneath the Australian Plate produced the volcanoes on New Zealand's…

Geology of Vanuatu Archipelago

This past week, the Vanuatu Archipelago of the southwestern Pacific Ocean has been in the news due to massive destruction wrought by Typhoon Pam.  The volcanic island chain consists of more than 80 islands and islets, stretching 720 miles (NNW to SSE) along the edge of the Pacific Plate, northeast of New Caledonia.

Part of a long volcanic arc that includes the Solomon Islands to their north, the islands of Vanuatu began to form during the Miocene Period (some 20 million years ago) as the northeastern edge of the Australian Plate dipped beneath the Pacific Plate; this subduction process continues today, manifest by earthquakes and volcanic eruptions.  Indeed, most of the archipelago has surfaced since the late Pleistocene (within the last 200,000 years).

Of course, this ongoing volcanism and land formation is partially balanced by the erosive force of tropical storms and rising sea levels related to global warming.  On the other hand, the rugged volcanic landscape has served to protec…

Reunion on the Platte

By mid February, migrant sandhill cranes begin to gather along an 80-mile stretch of the Platte River, in south-central Nebraska.  They are traveling northward from wintering grounds in West Texas, Mexico and eastern New Mexico, headed for northern Canada, Alaska and Siberia.

Their number will peak in late March, when 600,000 cranes stop to rest and feed along the Platte, and most will depart by mid April.  This reunion of sandhill cranes attracts hordes of humans as well and the annual Audubon Crane Festival is held in Kearney in late March.  Those unable to visit Nebraska are advised to check out the Rowe Sanctuary's Crane Cam, which gives one a feel for the sights and sounds of the rendezvous site (including the intense winds that frequently rake the Great Plains); my thanks again to Chuck Robertson, from Huntsville, Alabama, who brought the cam to my attention.

Cam viewing is best in the late daylight hours and during the hours just after sunrise, when the cranes move to and f…

Wildlife in the Mist

Low clouds, patchy fog and a cool mist enveloped central Missouri this morning and, as I reached Eagle Bluffs Conservation Area, a barred owl perched like a sentry along the entrance road.  Flocks of ducks, mourning doves and red-winged blackbirds pierced the humid air but my attention was soon drawn to a massive flock of geese on a flooded field.

Composed of snow geese and greater white-fronted geese, the restless and vocal flock was constantly in flux as some groups moved off to the north while others arrived from the south, circling above the field before choosing a site to land.  Smaller flocks of Canada geese fed in the adjacent stubble while mallards and blue-winged teal (the first I have seen this spring) speckled the deeper pools.  Other sightings on this cool, damp morning included bald eagles, common mergansers, killdeer, belted kingfishers, great blue herons, wood ducks and lesser scaup; an island of white pelicans was spotted on a distant lake, chorus frogs called from sha…

Beyond the Mud

Across the American Heartland, March is known for its muddy landscapes, cold rain, wet snow and raw, windy days.  But, to the naturalist, March has far more to offer than ugly weather and sloppy terrain.

After all, the month generally brings the first flowers of spring, including crocuses, hyacinths, snowdrops, early tulips, dandelions and the flowers of red maples and forsythia.  Greenery appears on our lawns, first as clumps of wild onion and then spreading to the grass itself.  As the soil thaws and the earthworms rise, American robins stalk those suburban carpets and, by the end of the month, the first young cottontails scurry between the shrub lines.  Out in the wetlands, waterfowl migrations are peaking and the first summer residents, tree swallows and eastern phoebes, make their appearance, serenaded by chorus frogs and spring peepers.  The hysterical calls of flickers echo from the woodlands where the drumming of their red-bellied, downy, hairy and pileated cousins has intensi…

Speed Birding

Most of our National Wildlife Refuges, Conservation Areas and large nature preserves are accessed by a network of graveled roads which permit close observation of the component habitats and their wild residents.  This provides an excellent opportunity for wildlife study and photography and experienced birders know that, by using their vehicle as a blind, they can observe and identify species at close range without spooking their quarry.

The roads also permit speed birding, a style utilized by those individuals more concerned with finding rare species than immersing themselves in the ecosystem.  Racing through the preserve, these veteran birders quickly identify birds by their silhouettes, plumage or behavior; ignoring the common species, they slow down only to check out unusual or unexpected birds, perhaps taking a photo for documentation.  After completing their tour, many contact their local birding society to report on rare species; for them, birding is a sport and keeping their na…

The Chad Basin

The Chad Basin is both a topographic and a geologic sedimentary basin that covers nearly 8% of the African Continent, stretching from southeastern Algeria to the northwestern Central African Republic and from central Niger to western Sudan; most of Chad, northern Cameroon and northeastern Nigeria also lie within the basin.  Lake Chad (elevation about 920 feet) lies at the center of the basin (though it is not the basin's lowest point).

Geologically, the Chad Basin is a broad depression of the Precambrian Shield upon which nearly 12,000 feet of Paleozoic, Mesozoic and Tertiary sediments have accumulated, deposited by inland seas or eroded from highlands that rim the basin.  Mega-Chad Lake, the precursor of Lake Chad, covered a large portion of the basin from about 40,000 to 3,000 years ago, draining to the Atlantic via the Benue and Niger Rivers; as the lake level fell, this outlet was lost and Lake Chad became a true basin lake, expanding and contracting with the regional climate.

First Wave of Pelicans

Light, patchy fog enveloped the Missouri River Valley just after dawn this morning.  At the Eagle Bluffs Conservation Area, flocks of geese and ducks wheeled above the refuge while groups of bald eagles (mostly immature) perched in the scattered trees.

In the southwest corner of the preserve, another mixed flock of snow geese and greater white fronted geese fed in the corn stubble, soon to depart for the next rest stop on their journey to the Arctic.  Among the ducks, lesser scaup and common mergansers were notably abundant though most migrant and wintering species were represented.  But the celebrities this morning were American white pelicans; two flocks, totaling 36 individuals by my count, were the first I have encountered this season.

Having wintered along the Gulf Coast, the pelicans are on their way to breeding lakes across the Northern Plains and Intermountain West.  They are common migrants through the Missouri River Valley, sometimes observed as early as February and general…

Romance or Predation?

By early March, many permanent avian residents of the American Midwest have already paired off for the breeding season; some, like geese and raptors, are monogamous (at least for the season) while others are not.  Among the most conspicuous of these early spring couples are bald eagles, Canada geese, red-tailed hawks and mourning doves.

Yesterday, a less common pair of residents strafed our Columbia neighborhood.  Zig-zagging through the trees, the powerful hunters moved in tandem, apparently searching for unwary songbirds; their broad wings, medium size and long, rounded tails revealed that they were Cooper's hawks, among our more aggressive raptors.  I wondered if they were engaged in cooperative hunting or if I was witnessing a courtship display.

In either case, the male must proceed with caution, lest romance or cooperation end in disaster.  Known to prefer larger prey such as flickers, pigeons, kestrels and sharp-shinned hawks, Cooper's hawks may even kill members of thei…

Summer's Leading Edge

Those of us who live in the Temperate Zones of Planet Earth generally recognize four seasons, based on astronomical, biological, meteorological and cultural events.  However, in my view, spring and fall are primarily transitional periods between our two major seasons: summer and winter; unlike the latter seasons, the timing and progression of spring and fall varies widely from year to year as stagnant weather patterns delay or accelerate their course.

During spring and fall, winter and summer battle for dominance, fueled by the changing intensity of solar radiation and an unruly jet stream; weather conditions and their effect on nature's cycle are far from predictable.  In some years, the crocuses bloom by mid February and tree frogs are calling from icy ponds by the end of the month; in other years, ice and snow coat the landscape well into March, delaying these early signs of spring.  While brief periods of warmth may occur throughout winter, the transition to summer must await …

Canvasbacks at Eagle Bluffs

In yesterday's post, I failed to include canvasbacks among my sightings at Eagle Bluffs (the error has since been corrected).  In fact, were it not for the large flock of snows and greater white-fronted geese, my report would have concentrated on those large diving ducks.

Indeed, I observed more canvasbacks at Eagle Bluffs yesterday than I have on any visit over the past seventeen years.  After breeding in the pothole country of northwestern North America, these elegant ducks travel south in large flocks to winter on coastal bays, large rivers or reservoirs of the southern U.S. and Mexico; migrations are primarily through the Mississippi and Pacific flyways.

Grebe-like in their habits, canvasbacks place their nests on floating vegetation; ten greenish eggs are generally produced.  The ducklings leave the nest soon after hatching, feasting on insects at the surface; adults, on the other hand, dive to feed on aquatic plants and invertebrates.   Rather clumsy on land, canvasbacks are…

Snows in the Snow

It was cold and snowy at Eagle Bluffs Conservation Area this morning; the air temperature was 20 degrees F.  Canada geese and mallards dominated the scene, their massive flocks swirling above the Missouri River floodplain.

Northern pintails, canvasbacks, American coot, ring-necked ducks, buffleheads, lesser scaup and mergansers (common, red-breasted and hooded) were also observed on the open pools and stoic great blue herons, dusted with snow, stalked the shallows.  Raptors included a half-dozen bald eagles, American kestrels and a fair number of northern harriers.

But the highlight of my visit was a huge, restless flock of snow geese (500 or more), accompanied by at least 200 greater white-fronted geese.  Having set down in a field along the eastern edge of the refuge, the vocal migrants would intermittently rise into the air, oblivious of the steady snow, before settling back in the corn stubble.  On their way to the Arctic, they'll likely rest and feed on the floodplain until t…

Black on White

Crossing the wintry Midwest today, there were few signs of life on the snow-laden farmlands; even the ubiquitous red-tailed hawks and European starlings were relatively sparse.  The lone exception was provided by flocks of American crows, picking through barnyards, feasting on carrion, gathering in the snowy corn stubble or cavorting above the winter landscape.

Members of the Corvid family, which includes crows, ravens, jays and nutcrackers, American crows are hardy, intelligent and aggressive birds.  Highly social, these omnivores cooperate in locating food and fending off predators; in winter, they are especially gregarious, roosting in large flocks.  As any birder knows, today's observation was not unusual; when severe weather or heavy snow cover discourage other species from venturing into open country, crows take advantage of their absence.

Many humans despise crows due to their raucous calls and aggressive behavior; after all, they sometimes raid feeders and gardens and, lik…

The March of Winter

March may be the first calendar month of spring but winter still grips most of the U.S.  Here in northeastern Ohio, the latest bout of snow began last night and is expected to persist through this evening.  While the afternoon high may reach the mid thirties (F) today, teens and twenties are forecast for the remainder of the week.

Indeed, it has been a long, brutal winter for most of the eastern U.S., especially across New England.  Today, a cold front lies across the Midwest and Mid-Atlantic region; a low pressure center, currently over western Kentucky, is sweeping moisture above the cold air, producing snow from southeastern Missouri to northwestern Pennsylvania.  As the low drifts eastward so will the snow, bringing yet another round of frozen precipitation for the Northeastern States.

On the positive side, this copious moisture will feed streams and wetlands; though flooding will surely develop across the lowlands, the watery landscape will provide nutritious feeding grounds for …