Vireos (Vireonidae Family)
Quail Ridge is inhabited by three sympatric species
of vireos – the resident Hutton’s and the summer visiting
Cassin’s and Warbling. All are similarly small, olive-colored
birds with rounded heads and short bills. They all build cup nests
near the ends of live tree branches or chaparral, and both sexes
incubate the eggs. In addition, they all will join mixed-species
flocks and expand their diets to include fruits in the winter.
The only non-migratory vireo in the western U.S.,
Hutton’s Vireo (Vireo huttonii) is typically a woodland
resident but may disperse locally. This sedentary tendency has facilitated
local divergence of the species – there are up to twelve subspecies
– and is the result of an affinity for evergreen trees. The
Pacific Hutton’s Vireo occupies the western half of California
year-round. These birds forage in the middle to upper tree regions,
actively gleaning insects and some arthropods from leaf surfaces.
Cassin’s Vireo (Vireo cassinii)
formerly was considered one of nine subspecies of the Solitary Vireo
(Vireo solitarius), until cytochromic92
testing substantiated its designation as a separate species in 199879.
Cassin’s Vireos breed throughout most of California, with
the exception of the Mojave Desert and Central Valley, and they
are confirmed breeders at Quail Ridge. Although both females and
males strongly defend their clutch of 3-5 (usually four) eggs, their
nests are moderately susceptible to parasitism by Brown-headed Cowbirds
(one nest at Quail was found to be parasitized). Cassin’s
Vireo is a deliberate foliage gleaner.
of five subspecies of warbling vireos occupy the United States:
a western form (Vireo gilvus swainsonii) and an eastern
form (V. gilvus gilvus) that occasionally enters California.
The western form breeds along the middle and northern California
coast and in parts of the Sierra, and winters in southern California
and Mexico. Although possible, it is unconfirmed as a breeder at
Quail Ridge. To catch insects, warbling vireos will frequently employ
hawking, stalking, and hovering in addition to gleaning. Although
they prefer upper and middle strata, they will forage from just
above the ground to near the top of the canopy. Warbling Vireos
are frequently parasitized by Brown-headed Cowbirds; V. g. swainsonii
is particularly susceptible because it has not developed the defense
of puncturing and ejecting cowbird eggs like its eastern counterparts.
Species and Guild Accounts
Listen and identify birds at: http://identify.whatbird.com/mwg/_/0/attrs.aspx
Photo Credits: Title, California Quail
(Joyce Gross), Hutton and Warbling Vireo photos (Will Turner) -
for more of his bird pictures see: http://www.tucsonbirds.org/BirdIDCenter.asp.
Cassin's Vireo photo (Peter LaTourrette) - for more of his bird
pictures see: http://www.birdphotography.com/.
For more pictures see: http://elib.cs.berkeley.edu/photos/browse_imgs/bird.html