Birds of the Sierra Nevada. Ted Beedy

especially along the coast. Nests are usually well shaded by foliage or rock overhangs. Nestlings are capable of flight in about 11 weeks but often return to the nest to receive food from the adults for several months after that. Young birds wander until attaining adult plumage at about five years, when they may breed for the first time.

      

      STATUS AND DISTRIBUTION Historically, Bald Eagles probably nested throughout the Sierra. As their population steadily recovers from mid-20th-century lows, their nesting range continues to expand as new sites are occupied each year. From October to March, they can be seen regularly though rarely throughout the Sierra with many at a time occasionally observed at some sites; such large winter gatherings may increase in the future as Sierra populations continue to grow. In the nonbreeding season, they travel great distances over many types of habitats but occur most often near large rivers, lakes, and reservoirs. During the breeding season (April through September), Bald Eagles are still rare in the central and southern portions of the Sierra.

      West Side. Fairly common to uncommon, pairs have nested as far south as Tuolumne County but will likely expand further southward in the future; large reservoirs along the full length of the range attract visiting Bald Eagles during the nonbreeding season, creating the possibility that new pairs will become established where conditions are favorable.

      East Side. Uncommon in the breeding season, breeding records south to Long Valley (Mono County) with possible breeding further south; fairly common nonbreeding visitors to large bodies of water with plentiful fish.

      TRENDS AND CONSERVATION STATUS After World War II, the use of DDT and other organochlorine compounds became widespread as insecticides to control mosquitoes and other insect pests. Breakdown products from these compounds accumulated in Bald Eagles and other birds of prey, causing eggshell thinning and almost complete reproductive failure in many species. In addition, Bald Eagle nests have been abandoned due to disturbances from nearby human activities. For these reasons the U.S. Fish and Wildlife Service and the California Department of Fish and Game listed the species as Endangered in 1978. A ban on use of DDT in the late 1970s, and greater protection of known nesting territories by federal and state agencies, allowed Bald Eagles to dramatically increase their population and expand their range in California and throughout the United States. Because of this recovery, the U.S. Fish and Wildlife Service reclassified Bald Eagles as Threatened in 1995 and delisted them entirely in 2007. They are still listed as Endangered and considered Fully Protected by California and are also protected under the federal Bald Eagle and Golden Eagle Protection Act. Historically huge Sierra salmon runs are now a thing of the past due to dam construction and water diversions, and this may limit the extent of the Bald Eagle’s recovery in this region, although construction of reservoirs has undoubtedly benefited the species.

      Northern Harrier

      Circus cyaneus

      ORIGIN OF NAMES “Harrier” from “hen-harrier,” a British name for the species’ habit of harrying poultry; circus from Gr. kirkos, a hawk, refers to the species’ circling flight; L. cyaneus, blue, for the male’s grayish-blue upperparts.

      NATURAL HISTORY One often sees these low-flying hawks hunting low over grasslands and marshes of the Sierra Nevada. Northern Harriers have an owl-like facial disk that funnels sound into large ear openings. While not hunting like owls in the dark, they do work very close to the ground in a “low patrol” fashion, where their excellent hearing helps them locate prey, even in dense cover. These hunting flights can be quite dramatic, as harriers hunt almost solely through active flight: “It oftenest moves in a huge zigzag course, quartering its territory like a hunting dog” (Dawson 1923). When prey is detected, the harrier may suddenly stop, perform an acrobatic downward turn, and plunge suddenly onto an unsuspecting vole, bird, or reptile.

      While many breeding pairs are monogamous, some male harriers maintain harems of two to five females, a rare behavior among hawks. In the Sierra the breeding season begins in late March or early April, when males are in frequent flight, performing energetic roller-coaster courtship displays that may include dozens of U-shaped dips. Both sexes carry grasses and other materials, but the females do the nest building alone. During incubation, males bring a steady supply of skinned and beheaded prey to the female, with the exchanges frequently occurring in flight with the male dropping the item and the female snatching it in midair. Their nests are well hidden in wet meadows or marshes, and recently fledged birds spend much of their time hiding in hidden pathways in the vegetation. Both parents feed the young, but males with extensive harems may ration their efforts to benefit just one or two nests. Juveniles can fly and can hunt independently about two months after hatching.

      In winter, the larger and more aggressive adult females defend territories with the best habitat, forcing males and juveniles to forage in less productive areas. Unlike most other hawks, sexes differ in appearance, with females brownish and adult males gray, black, and white. Both male and female harriers are brownish during their first year of life.

      STATUS AND DISTRIBUTION Found around the edges of the Sierra, harriers favor open areas of wetland, pastures, and grassland but can be seen foraging over sagebrush flats as well. After young birds fledge, until the arrival of snows they readily wander into the mountains and can be found over open slopes, rarely up to the Alpine zone. Local populations often increase in winter with the influx of birds from the north and east.

      West Side. Fairly common to uncommon, primarily associated with Central Valley wetlands, pasture, forage crops, and rice (in winter), but their breeding range extends from the lowest reaches of the Foothill zone up into open oak savanna in the north; in the south known nesters only in the Kern River Valley, at about 2,600 feet; during spring and fall migration they are frequently observed soaring in-transit over all habitats up to the Subalpine zone.

      East Side. Fairly common to uncommon, pairs breed locally throughout the Great Basin and scattered populations range to the base of the Sierra; common in low-elevation wet meadows, but historical overgrazing and development have impacted and fragmented their best habitats; sometimes breed at higher elevations (up to more than 6,000 feet) in wet mountain meadows.

      Sharp-shinned Hawk

      Accipiter striatus

      ORIGIN OF NAMES “Hawk” from Teutonic root hab, to grasp or seize; “sharp-shin” refers to the raised ridge on the front of the bird’s lower leg; accipiter from L. accipere, to take or seize; L. striatus, striped.