Yellow-throated Vireo Vireo flavifrons
Andrew Molera State Park, Big Sur Ornithology Lab
Monterey County, California
19 May 2001, Joseph Morlan

This morning we learned from the Monterey BirdBox that Steve Rovell found a singing Yellow-throated Vireo in the willows and sycamores adjacent to the Big Sur Ornithology Lab at Andrew Molera State Park. We were already planning a visit to this site, so Dan Singer, Robbie Fischer, and I drove down from Pacific Grove. There we met Steve Rovell and others who were still viewing the singing bird. We watched the vireo off-and-on for a considerable period of time and were afforded excellent views in good light. Others seeing the bird included Don Roberson and Rita Carratello.

The following description is based on notes taken while watching the bird:

A medium-sized vireo about the size of Cassin's Vireo (not present), and slightly larger than adjacent Chestnut-backed Chickadees.

The upperparts were olive-green on the crown, nape, back and face. This color contrasted with bold yellow spectacles which wrapped around the back of the dark eyes and forward over dark lore stripes to the upper mandible. The olive-green face also contrasted strongly with a bright neutral yellow throat and breast. The sides of the breast was dingy. The rest of the underparts were white, including the belly and undertail coverts, but the flanks were decidedly grayish.

The wings were gray with bold white wing bars, and narrow white tertial fringes. The tail was gray with no tail-spots, and was often held cocked up at an angle. The bill was thick, short and blunt; dark in color with a decided hook at the tip of the mandible, visible while the bird was singing. The legs were sturdy, and gray in color.

The bird sang most of the morning. The song was very similar to that of Cassin's Vireo but somewhat slower, hoarser and more deliberate. It consisted of well paced rising and falling phrases. The tempo was a little more upbeat than on some Yellow-throated Vireos I have seen in the past, and the bird was somewhat more active than is typical from my experience with the species in the East and in California.

Discussion

This appears to be an exceptional Spring for Yellow-throated Vireos with at least four individuals thus far. Previous sightings this month are from Orange County, Santa Clara County, and Marin County.