Warbler Guy, is it possible to ID the "Audubon's" Yellow-rumped Warbler vs. the "Myrtle" subspecies by call notes? Where do I learn more about telling call notes by bird species?

Good question, Kristen:

Here's one general answer, that I dare say is also an oversimplification of this complex topic.

First, you are probably aware from your smart question that a "call" note is a different and distinct vocalization than a "song," — the latter of which is typically a learned and memorize rendition sung in most cases by males as a rhythmic vocalization of one or more phrases (e.g., think of a loquacious Northern Mockingbird).

A "call" note is one element. 

Most songbirds express one call note, ala your question, above.

Thus: 

Obviously, Yellow-rumped Warbler individuals are NOT currently 
singing during the non-breeding season, but you do often hear 
their loud chip or call notes where the subspecies Audubon’s 
and Myrtle Yellow-Rumped Warbler forage during the non-breeding season.

This is the case throughout the San Francisco Bay area 
where I live. In the fall and through March (and, even, 
into April), most of the Yellow-rumped Warblers seen 
and heard occur as the Audubon's subspecies. 
Sometimes, I am able to spot a Myrtle 
subspecies individual....though for every, 
say, 100 Audubon's I see in the SF Bay 
Area, approximately one is a Myrtle subspecies.

(Note the Audubon's subspecies nests in 
a few higher elevations in the SF Bay Area, 
including Marin County where I live (20 miles 
north of the Golden Gate Bridge).)

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.

Regards, Daniel

warblerwatch.com
(hosts my resume and my "Birding Tours" 
information for N. and Central CA tours that 
I have conducted since 2001)

Warbler Guy, I'm planning an upcoming California birding tour and want to go with a San Francisco birding guide. As I prepare, where do I check for "rare" bird alerts that will reveal which rare California bird species are recent sightings?

Hi Davey:

Here's the answer to your question, above:

To see recent bird species sightings throughout California, feel free to check:

http://digest.sialia.com/?rm=all_lists

This link features a composite list of all California listserv sites.

Click on one or more as you please to see the latest bird sightings lists posted by
birders.

Questions?

Glad to help: danieledelstein@att.net

One "strange but true" facet of California birding relates to how most of the state soon expresses a touch of spring (already!), given the courtship dance of male Anna's hummingbird individuals are often observed this time of year (and especially by November and December, annually).

Initial egg laying by this common, year-round resident hummingbird species occurs as early as December. Multiple broods may be tended by a female during one breeding season, with July and August the latest months each year when final active nests are observed.

As for wood-warblers typically occurring on listservs currently in the SF Bay Area where I often serve as birding guide to hot spots such as Point Reyes National Seashore (Marin Co.) and Bodega Bay (Sonoma Co.), the once abundant in-migration Yellow Warbler (late summer through September) is now a rare sighting, with only the rare individual detected on local San Francisco Bay Area Christmas Bird Count forays.

More typical, it's common to see Yellow-rumped Warbler individuals in many habitats this time of year through March (Audubon's Yellow-rumped Warbler subspecies — Setophaga cornonata auduboni) is the most abundant subspecies in this species to observe, though the West Coast also attracts the occasional to uncommon Myrtle Yellow-rumped Warbler subspecies (Setophaga coronata coronata).

Feel free to review my web site's "Warbler ID Charts," if you wish additional info. and/or see the "Birding Links" articles and my "2017 Nature Watch Calendar" where several wood-warbler articles appear, among other information elements.

Regards, Daniel Edelstein
Consulting Avian Biologist,
Birding Guide,
& Birding Instructor (Merritt College, Oakland, CA)