Greater sage grouse, the largest grouse in North America, inhabit sage grasslands of the Intermountain West, from Colorado to the Columbia Plateau and from southern Alberta to southern Utah. Closely tied to their habitat, these grouse feed solely on the sage plant in the winter while supplementing that diet with a variety of forbs, insects and grasses during the warmer months. Unlike many game birds, they do not possess a muscular crop and cannot digest hard seeds.
Come spring, sage grouse gather in clearings (known as leks) at dawn and dusk, where the dominant males attract mates with ritualized strutting, tail fanning and a variety of noises from their air sacs; most of the females mate with only one or two of the performers. Nests are placed on the ground and females are solely responsible for both incubation and protection of the young; six to twelve eggs are generally produced. Able to forage soon after birth, the young are vulnerable to a wide range of predators, including snakes, prairie falcons, crows, magpies, badgers, coyotes, bobcats and owls.
Once abundant across the American West, greater sage grouse have long been threatened by habitat loss; their population, estimated to have been about 16 million in the early 1900s, has fallen to less than 500,000 today, a drop of 97% over the past century. The loss of sage grasslands to mining, ranching and oil production has been primarily responsible for this decline and efforts to list the greater sage grouse as an Endangered Species have been successfully blocked by Western Governors and their Federal colleagues. Perhaps a 99% population decline will be more convincing.
Tampilkan postingan dengan label Great Basin. Tampilkan semua postingan
Tampilkan postingan dengan label Great Basin. Tampilkan semua postingan
Selasa, 24 April 2012
Senin, 16 April 2012
Long-Billed Curlews
While crossing the stormy Plains yesterday afternoon, I encountered a small flock of long-billed curlews, attempting to fly into the teeth of an icy north wind. After wintering along the western Gulf Coast, in South Texas, in Southern California or in Mexico, this largest American shorebird returns to grasslands of the High Plains, Great Basin and Columbia Plateau for the warmer months.
Once on their breeding grounds, couples engage in courtship rituals, including dances, looping flights and preliminary nest site scooping by the male. The female eventually selects one of his open ground sites, engages in additional scooping and collects a variety of plant materials to place in the floor of the depression. Four eggs are deposited and incubated by both parents; like many game birds, the young are able to move about and feed soon after hatching and are attended by both parents for a week or so. Thereafter, the female parent departs to join other wayward mothers and juveniles in large feeding flocks while the father stays to watch over the youngsters until they are fledged. The long, down-curved bill of this curlew is used to probe mudflats, wet meadows and sandy shallows for a variety of invertebrates (worms, insect larvae, shrimp, sand crabs) and small amphibians; they may also snare grasshoppers, crickets and other insects from the grass and occasionally consume the eggs of other prairie birds.
Once common in parts of the Eastern U.S., long-billed curlews have retreated westward due to over-hunting and habitat loss to agriculture; fortunately, the western populations seem to have stabilized but remain sensitive to the health of shortgrass ecosystems. Small numbers of long-billed curlews may turn up on Atlantic beaches during the fall and winter months where they can be distinguished from whimbrels by the curlew's larger size, longer bill and unstriped crown and from the occasional Eurasian curlew by the latter's darker plumage, white rump and heavily streaked breast; the cinnamon wing linings of long-billed curlews also aid identification when this large shorebird is in flight.
Once on their breeding grounds, couples engage in courtship rituals, including dances, looping flights and preliminary nest site scooping by the male. The female eventually selects one of his open ground sites, engages in additional scooping and collects a variety of plant materials to place in the floor of the depression. Four eggs are deposited and incubated by both parents; like many game birds, the young are able to move about and feed soon after hatching and are attended by both parents for a week or so. Thereafter, the female parent departs to join other wayward mothers and juveniles in large feeding flocks while the father stays to watch over the youngsters until they are fledged. The long, down-curved bill of this curlew is used to probe mudflats, wet meadows and sandy shallows for a variety of invertebrates (worms, insect larvae, shrimp, sand crabs) and small amphibians; they may also snare grasshoppers, crickets and other insects from the grass and occasionally consume the eggs of other prairie birds.
Once common in parts of the Eastern U.S., long-billed curlews have retreated westward due to over-hunting and habitat loss to agriculture; fortunately, the western populations seem to have stabilized but remain sensitive to the health of shortgrass ecosystems. Small numbers of long-billed curlews may turn up on Atlantic beaches during the fall and winter months where they can be distinguished from whimbrels by the curlew's larger size, longer bill and unstriped crown and from the occasional Eurasian curlew by the latter's darker plumage, white rump and heavily streaked breast; the cinnamon wing linings of long-billed curlews also aid identification when this large shorebird is in flight.
Selasa, 03 April 2012
The Western Ibis
Cousin to the glossy ibis of the Southeastern U.S., the white-faced ibis winters along the Gulf Coast (from Louisiana to Texas), in valley wetlands of central and southern California and in Mexico. While some are permanent residents in these areas, most migrate through the central and western U.S. to breed on freshwater wetlands of the Northern Plains and Intermountain West.
Since wetland conditions tend to vary across the dry country of the Western U.S., these nomadic migrants are opportunistic, choosing their colonial nest sites based on the conditions that they find; for this reason, their numbers in any given area varies widely from year to year. Preferring broad, shallow wetlands with islands of vegetation, white-faced ibis nest in marsh grasses or in low trees along the shore. Both parents incubate the 3-4 eggs and participate in feeding regurgitated insects, worms, amphibians and small fish to the nestlings; the young are fledged within a month and are self sufficient by August.
Known to wander widely in late summer, small flocks of white-faced ibis turn up in the eastern U.S. on occasion but generally return to their traditional wintering grounds by mid autumn. Peak spring migrations across the Great Plains generally occur from mid April to early May and it is then that most of us encounter these attractive birds, stopping to rest and feed on shallow lakes, braided rivers or flooded fields.
Since wetland conditions tend to vary across the dry country of the Western U.S., these nomadic migrants are opportunistic, choosing their colonial nest sites based on the conditions that they find; for this reason, their numbers in any given area varies widely from year to year. Preferring broad, shallow wetlands with islands of vegetation, white-faced ibis nest in marsh grasses or in low trees along the shore. Both parents incubate the 3-4 eggs and participate in feeding regurgitated insects, worms, amphibians and small fish to the nestlings; the young are fledged within a month and are self sufficient by August.
Known to wander widely in late summer, small flocks of white-faced ibis turn up in the eastern U.S. on occasion but generally return to their traditional wintering grounds by mid autumn. Peak spring migrations across the Great Plains generally occur from mid April to early May and it is then that most of us encounter these attractive birds, stopping to rest and feed on shallow lakes, braided rivers or flooded fields.
Kamis, 08 Maret 2012
Mono Lake
Mono Lake is a 70 square-mile saline lake at the eastern foot of the Sierra Nevada Range, approximately 13 miles east of Yosemite National Park. Enclosed within a natural basin by the Sierra Batholith to its west and Pliocene-Pleistocene volcanic ranges to its north, east and south, the lake is fed by three primary streams (Lee Vining, Rush and Mill Creeks) and by freshwater springs along its floor. Having formed during the Pleistocene, about 1 million years ago, it is one of the oldest lakes in North America and is the largest lake completely within California.
As a basin lake, its size and depth are a balance between inflow from streams and springs and evaporative loss in the dry climate of the Basin and Range Province. Prior to 1941, its surface elevation hovered above 6400 feet but this was dramatically lowered by diversion of inflow to the Los Angeles Water System; legal challenges by conservation groups eventually restored most of the inflow by 1994.
Despite its high salinity (2.5 times that of ocean water) and alkalinity (which precludes fish survival), Mono Lake supports a spectacular ecosystem. Photosynthetic algae, feeding on minerals from the surrounding mountains, bloom in spring when snowmelt peaks. Feeding on the algae, brine shrimp and brine flies thrive in the lake shallows and provide vital nourishment for migrating shorebirds, eared grebes and phalaropes, among other species; indeed, Mono Lake was added to the Western Hemisphere Shorebird Reserve Network in 1991. California gulls and snowy plovers nest on Paoha Island and smaller islets, escaping predation by fox and coyotes. Beyond the abundant birdlife, Mono Lake is perhaps best known for its tufa towers of calcium carbonate, produced by the interaction of freshwater springs and the alkaline, mineral-rich lake waters. Students of geology will also appreciate the surrounding volcanic landscape, including the relatively recent Panum and Mono-Inyo craters, south of Mono Lake.
As a basin lake, its size and depth are a balance between inflow from streams and springs and evaporative loss in the dry climate of the Basin and Range Province. Prior to 1941, its surface elevation hovered above 6400 feet but this was dramatically lowered by diversion of inflow to the Los Angeles Water System; legal challenges by conservation groups eventually restored most of the inflow by 1994.
Despite its high salinity (2.5 times that of ocean water) and alkalinity (which precludes fish survival), Mono Lake supports a spectacular ecosystem. Photosynthetic algae, feeding on minerals from the surrounding mountains, bloom in spring when snowmelt peaks. Feeding on the algae, brine shrimp and brine flies thrive in the lake shallows and provide vital nourishment for migrating shorebirds, eared grebes and phalaropes, among other species; indeed, Mono Lake was added to the Western Hemisphere Shorebird Reserve Network in 1991. California gulls and snowy plovers nest on Paoha Island and smaller islets, escaping predation by fox and coyotes. Beyond the abundant birdlife, Mono Lake is perhaps best known for its tufa towers of calcium carbonate, produced by the interaction of freshwater springs and the alkaline, mineral-rich lake waters. Students of geology will also appreciate the surrounding volcanic landscape, including the relatively recent Panum and Mono-Inyo craters, south of Mono Lake.
Rabu, 25 Januari 2012
Harney Basin
Harney Basin is a geologic and topographic basin in southeast Oregon; while it sits adjacent to the northwest corner of the Great Basin, it is separated from that province by the massive fault-block of the Steens Mountain ridge. On its north side, the Harney Basin is bordered by the southern edge of the Blue Mountains while a high lava plain separates the basin from the watersheds of the John Day and Klamath Rivers to the northwest and southwest, respectively.
During warm interglacial periods of the Pleistocene, glacial meltwater from the adjacent highlands filled the Harney Basin, spilling northeastward into the Malheur River, a tributary of the Snake River. Today, as the climate has warmed through the Holocene, the floor of Harney Basin has become a high desert, receiving only 6 inches of precipitation each year; a low divide along the basin's northeast edge, formerly a spillway, now completes the basin topography and all streams flow inward toward Harney and Malheur Lakes, on the basin's floor. Burns, Oregon, is the only sizable town in this remote, high desert basin.
While most of the basin floor is high and dry, with elevations between 4000 and 5200 feet, Malheur Lake, fed by the Silvies River from the Blue Mountains and the Blitzen River from Steens Mountain, provides a rich and welcome oasis for migrant waterfowl, shorebirds, white pelicans and sandhill cranes. Home to many other species as well, the lake and its wetlands are protected as the Malheur National Wildlife Refuge; during seasons with heavy precipitation or snowmelt, Malheur Lake spills west toward Harney Lake, an ephemeral, salt pan lake that is the topographic sink of Harney Basin.
During warm interglacial periods of the Pleistocene, glacial meltwater from the adjacent highlands filled the Harney Basin, spilling northeastward into the Malheur River, a tributary of the Snake River. Today, as the climate has warmed through the Holocene, the floor of Harney Basin has become a high desert, receiving only 6 inches of precipitation each year; a low divide along the basin's northeast edge, formerly a spillway, now completes the basin topography and all streams flow inward toward Harney and Malheur Lakes, on the basin's floor. Burns, Oregon, is the only sizable town in this remote, high desert basin.
While most of the basin floor is high and dry, with elevations between 4000 and 5200 feet, Malheur Lake, fed by the Silvies River from the Blue Mountains and the Blitzen River from Steens Mountain, provides a rich and welcome oasis for migrant waterfowl, shorebirds, white pelicans and sandhill cranes. Home to many other species as well, the lake and its wetlands are protected as the Malheur National Wildlife Refuge; during seasons with heavy precipitation or snowmelt, Malheur Lake spills west toward Harney Lake, an ephemeral, salt pan lake that is the topographic sink of Harney Basin.
Sabtu, 31 Desember 2011
The Great Basin
Defined by its hydrology, the Great Basin is a large area of the American West within which the rivers and streams drain from an irregular ring of topographic divides toward the interior of the basin, never to reach the sea. The west edge of the Great Basin runs along the crest of the southern Cascades, the Sierra Nevada Range, the Tehachapi Range and the San Bernardino Mountains while the east edge follows the crest of the Wasatch Plateau and the westernmost Uintas. Along its northern boundary, an irregular, low divide separates the watersheds of the basin rivers (dominated by the Bear and Humboldt Rivers) from that of the Snake River. The southern edge of the Great Basin is even more complex, separating basin river watersheds from that of the Colorado River, extending southward into northwest Mexico.
Since the Great Basin is surrounded by topographic divides, winds are downsloping from all directions, warming and drying the air; as a result, the Basin floor, with elevations ranging from 6500 feet to below sea level (in Death Valley), is a mosaic of deserts, covered by sage grasslands, salt flats and, in parts of the Mojave, joshua trees. The largest lakes within the Great Basin are the Great Salt Lake and Utah Lake, both in Utah, Pyramid Lake, in northwest Nevada, and Lake Tahoe and the Salton Sea in California.
Within the Great Basin, Earth's crust is being stretched in an east-west direction, caught between the uplifts of the Sierra Nevada, Rocky Mountains and Colorado Plateau. This has created a maze of linear faults, aligned north to south, along which fault-block mountains have risen to produce waves of ranges, separated by broad, flat valleys; while this aptly named Basin and Range Province includes all of the Great Basin, it also extends southeastward into the Sonoran Desert.
Since the Great Basin is surrounded by topographic divides, winds are downsloping from all directions, warming and drying the air; as a result, the Basin floor, with elevations ranging from 6500 feet to below sea level (in Death Valley), is a mosaic of deserts, covered by sage grasslands, salt flats and, in parts of the Mojave, joshua trees. The largest lakes within the Great Basin are the Great Salt Lake and Utah Lake, both in Utah, Pyramid Lake, in northwest Nevada, and Lake Tahoe and the Salton Sea in California.
Within the Great Basin, Earth's crust is being stretched in an east-west direction, caught between the uplifts of the Sierra Nevada, Rocky Mountains and Colorado Plateau. This has created a maze of linear faults, aligned north to south, along which fault-block mountains have risen to produce waves of ranges, separated by broad, flat valleys; while this aptly named Basin and Range Province includes all of the Great Basin, it also extends southeastward into the Sonoran Desert.
Sabtu, 17 Desember 2011
The Owens Valley
The Owens River of southeast California rises along the eastern flank of the Sierra Nevada Mountains, at the southeast edge of Yosemite National Park. After flowing eastward through the Long Valley Caldera, the river angles to the south-southeast and begins its journey through the magnificent landscape of the Owens Valley.
The Owens Valley is a geologic graben, a block of crust that dropped between the parallel faults of the Sierra batholith to its west and the White-Inyo fault block mountains to its east; as the mountains rose on either side, this block slipped downward. The floor of the valley has an elevation of 4000 to 3500 feet (north to south) while its steep walls rise toward some of the highest summits in the Lower 48; the latter include Mt. Whitney in the Sierra Nevada (14,498 feet) and White Mountain Peak (14,252 feet) in the White Mountains. The latter range also includes Boundary Peak (13,167 feet), the highest point in Nevada, while the Inyo Mountains, known for their exposure of Cambrian sediments, top out below 12,000 feet.
Representing the southwest edge of the Basin and Range Province, the Owens Valley lies in the rain shadow of the Sierra Nevada and receives very little moisture from the east due to the high wall of the White and Inyo Mountains. The waters of the Owens River have thus long been diverted for crop production across the Valley and, since 1913, much of its flow has been directed into the Los Angeles Aqueduct, leaving Owens Lake, the natural terminus of the river, mostly dry. Back in the Pleistocene, when mountain glaciers fed the Owens River, its lake basin spilled to the east (around the southern end of the Inyo Range), merging with lakes from other Great Basin rivers to produce an inland sea across Death Valley and adjacent lowlands.
The Owens Valley is a geologic graben, a block of crust that dropped between the parallel faults of the Sierra batholith to its west and the White-Inyo fault block mountains to its east; as the mountains rose on either side, this block slipped downward. The floor of the valley has an elevation of 4000 to 3500 feet (north to south) while its steep walls rise toward some of the highest summits in the Lower 48; the latter include Mt. Whitney in the Sierra Nevada (14,498 feet) and White Mountain Peak (14,252 feet) in the White Mountains. The latter range also includes Boundary Peak (13,167 feet), the highest point in Nevada, while the Inyo Mountains, known for their exposure of Cambrian sediments, top out below 12,000 feet.
Representing the southwest edge of the Basin and Range Province, the Owens Valley lies in the rain shadow of the Sierra Nevada and receives very little moisture from the east due to the high wall of the White and Inyo Mountains. The waters of the Owens River have thus long been diverted for crop production across the Valley and, since 1913, much of its flow has been directed into the Los Angeles Aqueduct, leaving Owens Lake, the natural terminus of the river, mostly dry. Back in the Pleistocene, when mountain glaciers fed the Owens River, its lake basin spilled to the east (around the southern end of the Inyo Range), merging with lakes from other Great Basin rivers to produce an inland sea across Death Valley and adjacent lowlands.
Rabu, 05 Oktober 2011
The Elusive Ringtail
The ringtail, named for its bushy, banded tail, is a small, nocturnal omnivore of the western U.S. and northern Mexico. Extremely agile, these cousins of the raccoon favor semi-arid areas with rock outcrops and open woodlands; there they hunt small mammals, birds and lizards and seasonally feast on nuts and berries. Since they are active primarily at night, ringtails are seldom encountered by hikers and campers.
Though often called ringtail cats, due to their size and behavior, they are not felines; once domesticated by miners to control rodents, they are also known as miner cats. Ringtails are solitary for most of the year but pair off in late winter or early spring to mate; the litter of kits (usually 2-4) are born in late spring and stay with their mother through summer. Dens are usually placed in small caves or rock crevices but ringtails are superb climbers and often rest in trees.
Natural predators of ringtails include hawks, owls, coyotes, fox and bobcats. Those fortunate enough to escape these hunters often live 7-8 years in the wild and have been known to live 15 years or more in captivity.
Though often called ringtail cats, due to their size and behavior, they are not felines; once domesticated by miners to control rodents, they are also known as miner cats. Ringtails are solitary for most of the year but pair off in late winter or early spring to mate; the litter of kits (usually 2-4) are born in late spring and stay with their mother through summer. Dens are usually placed in small caves or rock crevices but ringtails are superb climbers and often rest in trees.
Natural predators of ringtails include hawks, owls, coyotes, fox and bobcats. Those fortunate enough to escape these hunters often live 7-8 years in the wild and have been known to live 15 years or more in captivity.
Senin, 13 Juni 2011
Utah's Powder Keg
Famous for deep powder that attracts skiers from across the globe, the Wasatch Front of Utah is about to unleash its bounty on those who live along its base. Thanks to a persistent atmospheric trough that produced a chilly, wet spring, the snowpack is near record levels and has barely begun to melt, a process that generally peaks in May. When summer heat suddenly arrives, a torrent of meltwater will sweep through the steep canyons of that majestic range, inundating the towns and cities that lie in its path.
Unlike in other areas of the country, the rivers that drop into the Great Basin soon spread across the flat terrain, forming broad, shallow lakes that evaporate in the intense sun of the high desert. Of course, Salt Lake City and other urban centers now occupy that basin and, when reservoirs are unable to contain the flow, flooding results. In light of the deep snowpack and delayed melting cycle, such a scenario appears to be unavoidable.
The bounty of mountain snow is vital to the ecosystems of the Western U.S., sustaining forests and producing corridors of vegetation across the semiarid landscape that lies below; without it, humans could not have colonized the region. But nature is fickle, bringing drought one year and floods the next; we must understand the risks that come with her varied landscapes and learn to live with her changing moods.
Unlike in other areas of the country, the rivers that drop into the Great Basin soon spread across the flat terrain, forming broad, shallow lakes that evaporate in the intense sun of the high desert. Of course, Salt Lake City and other urban centers now occupy that basin and, when reservoirs are unable to contain the flow, flooding results. In light of the deep snowpack and delayed melting cycle, such a scenario appears to be unavoidable.
The bounty of mountain snow is vital to the ecosystems of the Western U.S., sustaining forests and producing corridors of vegetation across the semiarid landscape that lies below; without it, humans could not have colonized the region. But nature is fickle, bringing drought one year and floods the next; we must understand the risks that come with her varied landscapes and learn to live with her changing moods.
Sabtu, 15 Januari 2011
Great Basin National Park
Just west of the Utah line, U.S. 50 crosses the Snake Range of east-central Nevada, among the highest mountain ranges in the Great Basin; indeed, Wheeler Peak, 13063 feet, which caps the southern portion of this Range, is the second highest summit in Nevada and the 12th most isolated peak in the U.S. (it is 232 miles to the closest higher summit). Like the other fault-block ranges of the Great Basin, the Snake Range is oriented north-south and formed along a fracture in the Earth's crust; the rise of the Sierra Nevada batholith, to the west, and the uplift of the Colorado Plateau and Rocky Mountain corridor, to the east, have stretched (and continue to stretch) the crust of this region.
Since 1986, Wheeler Peak has been the centerpiece of Great Basin National Park, which highlights the varied life zones of this stark landscape, from the high desert to the alpine tundra. Introduced at the Visitor Center, in Baker, Nevada, and accessed by the State's highest paved roadway (which ascends to 10,161 feet) the Park harbors a wide range of plant and animal life, drawn to the "sky islands" of this arid region. Among the Park residents are mountain lions, elk, mule deer, bighorn sheep, bobcats, porcupines and ring-tailed cats. Various bat species inhabit more than 40 caves in this scenic Park, the most famous of which are found in the Lehman Caves group, eroded from Cambrian limestone during the wet climate of the Pleistocene.
North of U.S. 50, which summits the Snake Range at Sacramento Pass (7154 feet), is the Mt. Moriah Wilderness Area. Harboring the same life zones and wildlife as the National Park, this region is reknowned for its massive alpine tableland, bordered by groves of bristlecone pine. The longest-lived trees on our planet, some of these pines germinated 5000 years ago.
Since 1986, Wheeler Peak has been the centerpiece of Great Basin National Park, which highlights the varied life zones of this stark landscape, from the high desert to the alpine tundra. Introduced at the Visitor Center, in Baker, Nevada, and accessed by the State's highest paved roadway (which ascends to 10,161 feet) the Park harbors a wide range of plant and animal life, drawn to the "sky islands" of this arid region. Among the Park residents are mountain lions, elk, mule deer, bighorn sheep, bobcats, porcupines and ring-tailed cats. Various bat species inhabit more than 40 caves in this scenic Park, the most famous of which are found in the Lehman Caves group, eroded from Cambrian limestone during the wet climate of the Pleistocene.
North of U.S. 50, which summits the Snake Range at Sacramento Pass (7154 feet), is the Mt. Moriah Wilderness Area. Harboring the same life zones and wildlife as the National Park, this region is reknowned for its massive alpine tableland, bordered by groves of bristlecone pine. The longest-lived trees on our planet, some of these pines germinated 5000 years ago.
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