Bell’s Vireo (Vireo bellii) is a small North American songbird.
The Least Bell’s Vireo (Vireo bellii pusillus) is an endangered subspecies which can be found in Southern California.
There are ongoing development projects to protect its habitat. The decline of the Least Bell’s Vireo is mostly due to an increase in grassland, probably due to wildfires.
- Length: 4.25 to 5 inches (12 – 13 cm)
- Dull olive-gray above and whitish below
- Faint white supercilium (line above each eye)
- Dark eyeline and eye
- White border beneath eye (lower half of eye ring)
- Faint white wing bars
- Grayish upperparts
- Whitish underparts with grayish wash to breast
- Thick bill with hooked upper beak
- Sexes similar
- Juveniles similar to adults
- Eastern birds are more olive than western birds
The small Bell’s Vireo is dull even by vireo standards. It is best told from other vireos by its facial pattern. The white eye ring of the Bell’s Vireo is broken in front of and behind the eye.
- The Hutton’s Vireo’s eye ring is thickest behind the eye and is broken at the top.
- The Gray Vireo has a complete eye ring.
- The White-eyed Vireo has yellow lores (the region between the eye and bill on the side of a bird’s head) and white eyes (adults).
- The Warbling Vireo is larger and has a bolder supercilium (line above each eye) that extends further behind the eye.
- Warblers have thinner, unhooked bills.
Nesting / Breeding
The Bell’s Vireos build well-camouflaged nests and are protective of its nest. However, given the opportunity, their nests are often parasitized by the Brown-headed Cowbirds, who lay their eggs in the Bell’s Vireo nests who raise their young as their own.