WatchList Species Account for Bell’s Vireo (Vireo
the list as a Red List Species
|Photo: Tom Grey
Bell’s Vireo breeds in the Southwest,
central states, and in southern coastal California, in addition
to northern Mexico. It winters primarily in western Mexico
south to Nicaragua.
Though it nests in early successional scrubby
areas, in the Southwest and California it depends for nesting
habitat on corridors of vegetation along rivers and streams.
Modification of such habitat through agriculture, grazing,
urbanization, and flood control and reservoir construction
and heavy parasitism by cowbirds have led to steep declines
in the numbers of Bell’s Vireos.
The subspecies in California, the Least
Bell’s Vireo, has been classified by the U.S. Fish and
Wildlife Service as endangered. Habitat restoration and cowbird
control have allowed its numbers in California to recover
somewhat, but its population there still numbers only in the
few hundreds. Throughout its range in the U.S. its numbers
have declined 2.8% per year between 1966 and 2001. Measures
adopted for its conservation in California have been adopted
elsewhere in the western part of its U.S. range.