Page "Bell's Vireo" Paragraph 2

The Least Bell's Vireo ( Vireo bellii pusillus ), is an endangered subspecies in Southern California.

Consideration of Bell's Vireo has been a factor in several land development projects, to protect Least Bell's Vireo habitat.

The decline of the Least Bell's Vireo is mostly due to a loss of riparian habitat and brood parasitism by the Brown-headed Cowbird.