The Bell's vireo is a small four inch bird with drab gray-green plumage above and white to yellow plumage below. The bird has a white eye ring and two pale wing bars. The feet and bill are bluish-gray.1 As a vireo, it is identified by having a thickened bill, heavy legs, and lethargic behavior. The song is some-what harsh and squeaky, sounding like: zheedle zheedle zheedle zhoo? (pause) zheedle zheedle zheedle zhee! The song has been likened to someone asking a question, and then answering it himself.2
Habitat: Bell's vireo inhabits lowland riparian areas with willows, mesquite, and seepwillows. The vireo prefers dense, low, shrubby vegetation in riparian areas.1 V. bellii is threatened by loss of habitat from agriculture, grazing, urbanization, and groundwater pumping. Decline of Bell's vireo has been observed in Arizona.1
Range: V. bellii breeds in North America and winters south of the United States-Mexico border. The breeding range includes southern California, Arizona, New Mexico, the central Great Plains and the Midwest southward to northern Mexico. Bell's vireo winters in Central and South America.
Diet: The vireo is an insectivore, feeding on caterpillars, beetles, bees and wasps, and small spiders. They move about slowly, taking food from branches and leaves.1
Reproduction: V. bellii breeds May through July. Three to five white, speckled eggs are laid in a small, bowl-shaped nest. Cowbird nest parasitism affects up to seventy percent of all nests.1 Bell's vireo abandons the nest if parasitized, and reproductive success is lowered. Severe weather and predation also affects productivity.1
Status: Bell's vireo is listed as a migratory bird under the Migratory Bird Treaty Act.
Bell's Vireo in Pima County: Bell' s vireo has been observed in the Cienega Creek Natural Preserve,3 and along the effluent-dominated Santa Cruz River.4 This species also occurs in Saguaro National Park, Organ Pile National Monument, Buenos Aires National Wildlife Refuge, Tucson Mountain Park, and Colossal Cave.
1. BISON-M. 1997. "Bell's Vireo (Vireo bellii)." New Mexico Game and Fish Department.
2. Peterson 1961, et al BISON-M. 1997. "Bell's Vireo (Vireo bellii)." New Mexico Game and Fish Department.
3. Pima County Parks and Recreation Department. Cienega Creek Natural Preserve Bird Checklist. 9/3/92.
4. Pima County Flood Control District and ENTRANCO. 1998. Biological Studies: High Plains Effluent Recharge Project Marana, Pima County, Arizona. Appendix B.