Birds of the Sierra Nevada. Ted Beedy
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fire, destined to be gradually replaced by forest. In other spots, where the soils cannot support forest, the chaparral may represent a relatively permanent condition.
SUBALPINE ZONE
Lodgepole Pine Forests
North 7,500 to 9,000 feet; South 8,000 to 9,500 feet
Mountain lakes and springs spawn tiny streams that meander through meadow grasses and open stands of lodgepole pine. These pines also grow in dense groves that dominate the Subalpine zone, especially in the northern and central Sierra on both slopes, where they are sometimes joined by mountain hemlocks. Here and there, majestic specimens of western juniper occupy isolated, prominent cliffside locations. These trees, second only to the giant sequoia in longevity among Sierra trees, often bear the scars of numerous lightning strikes. Echo Summit (U.S. 50), Donner Summit (Interstate 80), and Tuolumne Meadows in Yosemite National Park have good examples of lodgepole pine forests. Hardy Mountain Chickadees reside in these forests year-round, moving along sprays of conifer needles and swinging down to inspect them from below. Dusky Flycatchers and Ruby-crowned Kinglets sound their familiar calls from forest edges and open ridge lines, while flocks of Red Crossbills and Pine Grosbeaks rove the treetops, even in winter. Hairy and Black-backed woodpeckers along with Williamson’s Sapsucker and Northern Flickers attack dead and dying lodgepole pines.
Lodgepoles growing at the edges of wet meadows and streams provide important nesting strata and cover for species closely associated with riparian habitats (this includes many migrating Neotropical songbirds such as flycatchers, vireos, warblers, and so on). The abundance of nesting and migratory songbirds draws predatory birds such as Cooper’s and Sharp-shinned Hawks, and Northern Goshawks. These hawks may nest in lodgepole pine forests but more frequently use them as hunting sites for ambushing prey, primarily birds but also rodents.
Subalpine Pine Forests
North 9,000 to 10,000 feet; South 9,500 to 11,500 feet
Backpackers head for these high forests where serrated ridges, perpendicular cliffs, and massive granite domes form spectacular vistas. On both sides of the Sierra, wind-sculpted whitebark pines grow with stunted lodgepoles on exposed ridges and north-facing slopes up to treeline. In the southern Sierra, erect stands of foxtail pine largely replace the gnarled whitebarks. The higher slopes of the Great Western Divide in Sequoia and Kings Canyon National Parks and the areas near Tioga Pass in Yosemite National Park have good examples of subalpine pine forests. Clark’s Nutcrackers and Pine Grosbeaks bound from tree to tree searching for pine nuts but dive for cover if the shadow of a Prairie Falcon skims by. Mountain Bluebirds, Dark-eyed Juncos, and “Mountain” White-crowned Sparrows forage in open, rocky areas. Here they are also joined by Common Ravens that prey on small birds and their eggs and nestlings and search for road-killed animals along high mountain roads.
FIGURE 4 Subalpine zone
ALPINE ZONE
Alpine Fell-Fields
North 8,500 to 10,800 feet; South 9,500 to >14,500 feet
The line of demarcation between the upper subalpine pine forests and treeless Alpine meadows is known as “timberline,” the point where trees cease to exist because of extremes in climate, shallow rocky soils, and high elevation. Here, freezing temperatures are possible any day of the year, and even the intense high-elevation sun does little to warm the cool, clear air. Life in these habitats is severe, and most plants are stunted by high winds, bitter cold, and shallow soils. Herbaceous plants dominate Alpine fell-fields, but stunted willows and other dwarf shrubs occur here as well. North of the Tahoe region, few peaks exceed 9,000 feet and alpine areas are limited to the summits of a few mountains, such as the Sierra Buttes in Sierra County, Castle Peak in Nevada County, and Granite Chief in Placer County. Farther south, many peaks exceed 13,000 feet, including Mount Whitney (14,496 feet), the highest mountain in the contiguous 48 states. Alpine environments are particularly extensive in Yosemite and Kings Canyon National Parks. Most Sierra Alpine fell-fields occur above the reach of highways, but a short hike from Carson Pass (Highway 88), Sonora Pass (Highway 108), or Tioga Pass (Highway 120) puts one amid the rugged cliffs, glacial cirques, and rock gardens of this zone.
In summer, wildflowers bloom profusely in Alpine fell-fields, and Dark-eyed Juncos and “Mountain” White-crowned Sparrows forage near shrubby willows. Gray-crowned Rosy- Finches feed on low turf or snow banks, and American Kestrels hover above. Mountain Bluebirds perch on boulders and dart out to snatch flying insects, the stunning blue of their plumage rivaling the alpine sky. American Pipits, Horned Larks, and Dark-eyed Juncos, as well as small mammals, attract raptors (especially during migration) such as Sharp-shinned and Cooper’s Hawks, Prairie Falcons, and Red-tailed Hawks. The summer flowering season coincides with an influx of hummingbirds that are either in migration or seeking relief from the summer drought and heat of the foothills. Rufous (in migration) and Calliope Hummingbirds can be abundant around particularly lush flower patches. Rock faces, boulder fields, and talus dominate much of the landscape in the Alpine zone, providing abundant habitat for Rock Wrens.
FIGURE 5 Alpine zone
EAST SIDE ZONE
Pine Forests
North 3,500 to 7,500 feet; South 3,000 to 8,500 feet
Growing in the Sierra rain shadow, pine forests of the East Side are generally more open and have smaller trees than the similar forests of the West Side. Easily seen along Highway 395, especially to the north of Mono Basin, they are dominated overwhelmingly by Jeffrey pines, but ponderosa pines are sometimes found as scattered individuals, or isolated pockets within larger Jeffrey pine stands, from Tahoe Basin north. Farther south, ponderosas are almost entirely replaced by Jeffrey pines, where higher elevations and associated colder temperatures combine to make soils drier. Some of the larger East Side basins, such as those surrounding Lake Tahoe and Mammoth Lakes, have extensive red fir and mixed conifer forests much like those on the West Side. Other tree species found on the East Side include western juniper, white fir, and lodgepole pine. East Side pine forests often have a dominant understory of Great Basin shrubs such as big sagebrush, bitterbrush, and rabbitbrush, along with numerous grasses and herbs. Some characteristic birds of these forests include Gray and Dusky Flycatchers, Pygmy Nuthatches, Clark’s Nutcrackers, and Red Crossbills.
Pinyon-Juniper Forests
North 3,500 to 8,500 feet; South 3,000 to 9,000 feet
At lower elevations of the East Side is an even drier habitat, pinyon-juniper forest, which is almost nonexistent on the West Side except at the southern end, where extensive stands occur in the drainages of the South Fork Kings River, the Kern River, and the South Fork Kern River. Highway 395 crosses through miles of this habitat where shrubby single-leaf pinyon pines grow in open stands, sometimes mingling with Utah junipers and Jeffrey pines interspersed between Great Basin shrubs like sagebrush, curl-leaf mountain mahogany, bitterbrush, and rabbitbrush. Bird species that tend to be more common in these forests than in pine forests are Pinyon Jays and Townsend’s Solitaires; Juniper Titmice occur in these habitats in the Mono Basin.
FIGURE 6 East Side zone
Great Basin Scrub
North 3,500 to 6,500 feet; South 3,000 to 7,000 feet
What may appear as a monotony of silvery-gray to olive-green shrubs in the lowlands of the East Side is often a floristically diverse assemblage of aromatic plants. Bitterbrush and sagebrush are the dominant shrubs, but a wide variety of other shrubs, perennial and annual forbs, and bunchgrasses may be found. Scattered emergent pines and large stands of curl-leaf mountain mahogany are also common. In large areas only the shrubs remain, forming the dominant habitat of the Great Basin. Sage-brush scrub also extends up to high elevations on dry hillsides of the East Side and locally west of the crest, as near Donner Summit. Driving the back roads through these scrubby habitats at dawn or dusk, one might flush