spring, oak woodlands come alive with the songs of Orange-crowned and Black-throated Gray Warblers, and the roughly whistled notes of Ash-throated Flycatchers. The Hutton’s Vireo’s monotonously repetitive song is a frequent sound in stands dominated by live oaks. White-breasted Nuthatches search the deeply furrowed bark of these trees and sound their nasal, hornlike calls. Northern Pygmy-Owls hide in these canyons by day and emerge at dusk to hunt for songbirds. In the Mother Lode country of the central Sierra, Highway 49 cuts through broad expanses of foothill woodland and chaparral, where one might still spot a Greater Roadrunner. On nearly any turnout, the strident calls of Western Scrub-Jays or Oak Titmice can be heard. California Quail work through tangles of poison oak, and Acorn Woodpeckers flash back and forth between trees, flycatching, chattering, and tending their acorn caches.
Foothill Chaparral
North <500 to 4,500 feet; South 500 to 5,500 feet
Impenetrable seas of brush cover hot, dry slopes the length of the Sierra foothills. Interspersed with foothill woodlands, chaparral vegetation generally occupies the steeper, more arid exposures, and the most extensive stands occur south of the San Joaquin River. Turnouts along the new Priest Grade (Highway 120), near Ash Mountain in Sequoia National Park (Highway 198), and the near vertical slopes above the South Fork Kern River (Highway 178) provide easy places to view these habitats. Visitors to foothill chaparral will notice pungent odors of chamise, whiteleaf manzanita, buckbrush, coffeeberry, and shrubby oaks filling the air. These shrubs grow together in thickets forbidding to people but offering shade and shelter to birds. Chaparral birds usually sing, defend territories, and forage in the cool, early morning hours.
Presunrise visits to these arid shrublands are often rewarded by a chorus of Common Poorwills, Wrentits, California Thrashers, Lazuli Buntings, and Spotted and California Towhees. As early as January, Anna’s Hummingbirds defend patches of shrubs with squeaky calls, and in spring Blue-gray Gnatcatchers and “Bell’s” Sage Sparrows (in chamise chaparral) raise their families within this protective cover. Birds can be particularly abundant in foothill chaparral habitats because they exist below the snow zone and because many native shrubs, such as toyon and poison oak, produce fruits that attract such species as American Robins, Cedar Waxwings, and Hermit Thrushes.
Foothill chaparral is a fire-prone system and the health and diversity of this habitat depends on fire. Many of the shrubs can survive fire and sprout from their burned stumps. Many others produce seeds than can only germinate after a fire. This habitat goes through a postfire succession, analogous to that of conifer forests, but at a much-accelerated pace. The open ground following a fire soon fills with a dazzling array of wild flowers. In the first postfire years birds like Rufous-crowned Sparrows, Lazuli Buntings, and Lawrence’s Goldfinches find conditions perfect. As the chaparral grows denser over time, new species appear and others depart. When the habitat becomes heavily overgrown and the shrubs reach their maximum height and density, bird diversity tends to decline, awaiting the next fire to begin the cycle again.
LOWER CONIFER ZONE
Ponderosa Pine Forests
North 2,000 to 6,000 feet; South 2,500 to 7,000 feet
Rising above the heat and haze of the Foothill zone, the Lower Conifer zone is where many people first feel they have reached the mountains. Breezes rustle the trees and, though hot in summer, these forests are distinctly cooler than the lowlands. They also receive more rainfall and snow, enabling them to survive the summer drought. Historically, ponderosa pines were the most common and widespread trees in the Lower Conifer zone because they tolerate hotter and drier climates than most other West Side conifers. Also called “mid-montane conifer forests” by some authors, a variety of other conifers including incense cedars, white firs, Douglas-firs, and sugar pines may now outnumber the ponderosas in mixed stands depending on fire history, elevation, and local conditions.
Before European settlement, these forests experienced frequent, low- to mid-intensity wildfires (primarily surface fires) that were a major factor influencing stand density, structure, and species composition. A policy of fire exclusion, or suppression, during the 20th century, along with the selective harvest of many large pines, has significantly changed fire behavior and led to an increase in fire severity and the number of infrequent but high-intensity, stand-destroying fires. In areas where fire has been prevented for many years, shade-tolerant white firs and incense cedars often outnumber the pines and oaks. In many ponderosa pine forests, kit-kit-dizze (a member of the rose family) covers the forest floor, and its pungent odor permeates the forest and clings to boots and clothing, earning it another name: “mountain misery.”
Large snags (i.e., greater than 24 inches diameter-at-breast-height) and decaying portions of living trees offer nesting cavities for Pileated Woodpeckers, Northern Flickers, and Western Screech-Owls. A variety of woodpeckers, Red-breasted Nuthatches, and Brown Creepers patrol the bark of conifers, while Warbling Vireos, Yellow-rumped Warblers, Black-headed Grosbeaks, and Western Tanagers make music from above. Near campgrounds and other developed areas, Steller’s Jays squawk and patrol their picnic tables, and Brewer’s Blackbirds strut across the pavement.
Pine-Oak Woodlands
North 2,000 to 6,500 feet; South 3,000 to 7,000 feet
Within the Lower Conifer zone, hardwood species like California black oaks, Pacific madrones, and bigleaf maples often intermingle with pines and other conifers. Black oaks, with dark trunks and bright green leaves, grow in patches mixed in with conifers—especially on open, rocky ridges and in forest clearings. These deciduous oaks turn gold in fall like the aspens, willows, and cottonwoods. The madrones and maples favor cool, wet drainages. Black oaks harbor hordes of caterpillars and flying insects that attract Nashville Warblers, Black-throated Gray Warblers, and Cassin’s Vireos to forage and sing. The high diversity of birds in these habitats is driven by an abundance of insects and nutrient-rich acorns. Accordingly, such acorn-consuming species as Western Scrub-Jays, Steller’s Jays, Acorn Woodpeckers, Mountain Quail, and Band-tailed Pigeons are common residents.
FIGURE 2 Lower Conifer zone
Oaks also provide nutritious sap that exudes from wounds in the bark caused by insects, tree falls, fire, and Red-breasted Sapsuckers. The sap provides feeding opportunities for the sapsuckers as well as for hummingbirds and warblers like Yellow-rumps and Orange-crowns. The high-protein seeds of many broadleaved trees are eaten by a long list of birds, including White-breasted and Red-breasted Nuthatches, Chestnut-backed and Mountain Chickadees, Dark-eyed Juncos, and Spotted Towhees.
UPPER CONIFER ZONE
Mixed Conifer Forests
North 5,500 to 7,500 feet; South 6,000 to 8,000 feet
As one proceeds up the West Side, ponderosa pines of the Lower Conifer zone blend into the cooler, moister, mixed conifer forests of the Upper Conifer zone. Mixtures of four or five species of conifers are typical in these forests, as the name of this habitat suggests. At places such as Crane Flat in Yosemite (Highway 120) and near the Giant Forest in Sequoia National Park, Jeffrey pines, with large cones and an aroma like vanilla rising from their bark, out-number ponderosas. Shade-tolerant white firs are often the most abundant trees, but usually incense cedars, Douglas-firs, sugar pines, and even a few red firs grow there, too. Black oaks reach this high but are fewer than farther down. Where the soil is rocky or wet, especially near meadows, lodgepole pines may grow in scattered stands. Giant sequoias, the world’s largest known living things, occur naturally only in the western Sierra, primarily in the Upper Conifer zone. A few grow as far north as Placer County, but most of the 75 groves are south of the Kings River and the largest, most majestic stands are in Sequoia National Park and Giant Sequoia National Monument.
Historically,
