Jasper (in Fresno), that’s a fine question. Here’s some simplified thoughts: 1) Depending on when you’re pursuing wood-warblers, I vary where I go — and I’ll limit my answer to the northern California area where I typically guide birders on outings; 2) That written, it’s often best to visit forested areas featuring needle (conifer) trees for finding species such as Hermit (male, below photo) and Black-throated Gray Warbler whose greatest numbers begin returning to breeding grounds in, say, Marin County (1st county north of the Golden Gate Bridge) by April, while MacGillivray’s is far more uncommon and returns a little later to sporadic SF Bay Area nesting venues;

3) Other wood-warbler species in the SF Bay Area and close to it may be year-round, including Common Yellow-throat, Yellow-rumped Warbler (nests at higher elevations at selected Bay Area locations), and, more rare) Yellow Warbler (extirpated/locally extinct in most of the eight SF Bay Area counties; and 4) Townsend’s is restricted to the non-breeding season, but is common and easy to find from autumn through early spring throughout the SF Bay Area. Obviously, in sum, the five aforementioned species are FAR fewer than Midwestern and East Coast diversity and numbers. And, as mentioned, my overview above is a general introduction* to which species are potential observations. (* = You may have noticed I did not mention Yellow-breasted Chat, which is no longer designated a wood-warbler and is in its own family.)