On September 24, Ron Thorn discovered an ABA Code 4 Dusky Warbler in a patch of fennel in San Mateo County, California. The bird has been fairly reliable in this spot, which just south of San Francisco and notably just north of the San Francisco Airport. I can’t immediately recall a more convenient bird for out of town chasers.
The bird has been seen frequently in its patch off of Marina Boulevard, just south of Oyster Point Park in South San Francisco. Birders are urged to resist the impulse to traipse into the fennel patch to flush it, as it shows itself regularly and calls often.
Dusky Warbler is one of the Eurasian Phylloscopus warblers, breeding primarily in east Asia and wintering in southeast Asia. Most records in the ABA Area come from western Alaska (20-30 in the last 15 years, most in fall), including at least one on Middleton Island in the Gulf of Alaska. Additionally, there are a surprising number of records of the species from California, of which this is the 11th or so. The most recent were in 2015 and 2008. Notably, British Columbia, Washington, and Oregon, have yet to record this species. Howell, et al, suggests in Rare Birds of North America, that the route taken by drift migrants like Dusky Warbler simply bypass these areas.