Warbler Guy, which West coast warbler vagrants are the most common ones to see? Do vagrant warblers also appear on the East Coast?

Good question, Hogie (in Portland).

Answer:

On the West Coast, say, on the Outer Point of Point Reyes in N. CA, the most typical East Coast vagrants to see in the fall include Palm, Blackburnian and Blackpoll. Other species that often appear annually: Black-throated Blue, Black-and-white, Magnolia, and Chestnut-sided Warbler.

(Blackpoll Warbler, shown above.)

As for the East Coast, it's not as common in autumn to have West Coast breeding warblers show up, but it does occur.

One reason relates to the orientation error displayed by migrating warblers. For many vagrants seen on the West Coast, the cause is due to first-year individual having an innate faulty brain, causing them to navigate south, then west — instead of south and, then, east toward Latin American expanses.
In traveling west by mistake, these newborn warblers continue as far as the land will take them — such as to the far western extreme of Point Reyes National Seashore. Unfortunately, these vagrants meet an unfortunate fate as they eventually continue moving west over the ocean.

Is it possible to distinguish the call notes of Audubon’s vs. Myrtle Yellow-rumped Warbler during the non-breeding season where they occur together?

Is it possible to distinguish the call notes of Audubon’s vs. Myrtle Yellow-rumped Warbler during the non-breeding season where they occur together?

Answer:

Obviously, these birds are NOT now singing during the non-breeding season, but you do often hear loud chip or call notes where Audubon’s and Myrtle Yellow-Rumped Warbler patrol during the non-breeding season.

This is the case throughout the San Francisco Bay area where I live. In the fall and through March, most of the Yellow-rumped Warblers seen and heard occur as the Audubon's subspecies, though a Myrtle subspecies individual is sometimes spotted.

In many cases you can hear how the Myrtle (one of the subspecies of the Yellow-rumped Warbler species) has a flatter and softer chip note than the Audubon’s.

The “ch” component of the call note is weaker for the Myrtle and it often gives many calls in rapid succession.

However, be careful. Intergrades (individuals that display visual characteristics specific to both Audubon’s and Myrtle) may announce call notes of the other subspecies. In other words, it’s possible to see a bird that looks like an Audubon’s, but it’s call note sounds like a Myrtle. This individual could likely be an intergrade.