Bellvireo

Bestimmung

Measurements:

Taxonomie

Wissenschaftlicher Name

Vireo bellii

Autorität

Audubon, 1844

Ordnung

Passeriformes

Familie

Vireos

Gattung

Vireo

Verbreitung und Lebensraum

Zugverhalten

Complete migrants

Verhalten

Bell's vireos often use dense shrubbery including willows (Salix spp.), mulefat (Baccharis glutinosa), California wild rose (Rosa californica), mugwort (Artemisia douglasiana), Fremont cottonwood (Populus fremontii), and Western poison oak (Toxicodendron diversilobum) shrubs or vines as nesting locations. Bell's vireos make a well-camouflaged nest but when found they will stand its ground against intruders. As with many other North American songbirds, brown-headed cowbirds parasitise Bell's vireo nests, letting the vireos raise their young.<p>Historically, the least Bell's vireo was a common to locally abundant species in lowland riparian habitat, ranging from coastal southern California through the Sacramento and San Joaquin Valleys as far north as Red Bluff in Tehama County. Populations also occurred in the foothill streams of the Sierra Nevada and Coast Ranges, and in Owens Valley, Death Valley, and scattered locations in the Mojave Desert. Least Bell's vireos winter in Baja California Peninsula. Unlike during the breeding season, they are not limited in winter to willow-dominated riparian areas, but occupy a variety of habitats including mesquite scrub within arroyos, palm groves, and hedgerows bordering agricultural and residential areas. At the time of endangered species listing by the U.S. Fish and Wildlife Service in 1986, it had been extirpated from most of its historic range, and numbered just 300 pairs statewide. Populations were confined to eight counties south of Santa Barbara, with the majority of birds occurring in San Diego County. In the decade since listing, least Bell's vireo numbers have increased six-fold, and the species is expanding into its historic range. In 1998, the population size was estimated at 2,000 pairs. Nesting least Bell's vireos have recolonized the Santa Clara River in Ventura County, where 67 pairs nested in 1998, and the Mojave River in San Bernardino County. The northernmost reported sighting in recent years is of a nesting pair of least Bell's vireos near Gilroy in Santa Clara County in 1997. Roughly half of the current least Bell's vireo population occurs on drainages within Marine Corps Base Camp Pendleton in San Diego County, particularly in the lower Santa Margarita River.

Schutzstatus

Bestandstrend

rising