Accession Number : ADA322886

Title :   Ecology and Conservation of the Endangered Least Bell's Vireo,

Corporate Author : FISH AND WILDLIFE SERVICE SACRAMENTO CA ENDANGERED SPECIES OFFICE

Personal Author(s) : Franzreb, Kathleen E.

PDF Url : ADA322886

Report Date : MAR 1989

Pagination or Media Count : 25

Abstract : At one time considered common, the least Bell's vireo (Vireo bellii pusillus) was distributed throughout the Central Valley and other low elevation riverine systems in California and Baja California, Mexico, but now has been extirpated from the majority of its breeding range. Habitat loss from agricultural, urban, and commercial developments, flood control and river channelization projects, livestock grazing, and other activities has severely restricted the vireo's range. Limited reproductive success of the vireo as the result of nest parasitism by the brown-headed cowbird (Molothrus ater) in concert with habitat loss has resulted in a decline in the overall vireo population to about 300 breeding pairs. Extensive suitable riparian habitat for the least Bell's vireo must be secured and protected so that the population can increase and be maintained in perpetuity. Additional information on vireo population ecology, genetics, and biological requirements should be obtained and assessed to maximize reproduction. Demographic data will aid in determining the reproductive rate that is necessary to sustain the subspecies on a perpetual basis. High quality, early successional stage riparian woodland is essential for providing adequate nesting habitat. In areas with active cowbird control programs, vireo productivity apparently has been enhanced. An expansion of such efforts and a long-term commitment to cowbird control and vireo nest monitoring to remove cowbird eggs and young will be essential. Methods to reintroduce vireos into the Central Valley and other areas within the historical range that are presently unoccupied should be evaluated.

Descriptors :   *HABITATS, *ENDANGERED SPECIES, *TAXONOMY, *ECOLOGY, *REPRODUCTION(PHYSIOLOGY), CONTROL, BIOLOGY, DEMOGRAPHY, HISTORY, CALIFORNIA, RIVERS, PARASITES, BANKS(WATERWAYS), EGGS, AGRICULTURE, VALLEYS, GENETICS, FLOOD CONTROL, MEXICO, GRAZING, LIVESTOCK, LOW ELEVATION, BREEDING, NESTING(ANIMALS), BAJA CALIFORNIA.

Subject Categories : Anatomy and Physiology
      Ecology

Distribution Statement : APPROVED FOR PUBLIC RELEASE