Saturday, October 10, 2009

Warbler Guy: What does Myrtle vs. Audubon's Warbler mean? Are not they both Yellow-Rumped Warbler?

Thanks, Jill in Ocala, Fl.......No worries, Jill —
as even the experts have trouble figuring out how Audubon's and Myrtle fit into the systematic scheme by which Yellow-Rumped Warbler occurs in the majority of states, including Alaska.

Living in a vast range that stretches from our 49th state to Guatemala, consider how this common to abundant species has confounded taxonomic researchers over the years. In turn, it's not surprising that some birders are, likewise, challenged as to what to call a Yellow-Rumped when they see it. Myrtle? Audubon’s? Hooveri? Intergrade (i.e., Hybrid)? — if you’re in Alberta or British Columbia during the breeding season and note a Yellow-Rumped that shares field marks of both Myrtle and Audubon's).

So, given space limitations here, and based on the need to oversimplify the reasons for the split of this species into subspecies (and what a subspecies means in terms of its definition), here’s the current organizatonal "flow-chart" that the experts (e.g., citing approval from the American Ornithological Union that is the ultimate soothsayer in deciding this bird's classification nomenclature) have established for the Yellow-Rumped Warbler:

Five subspecies occur in the Yellow-Rumped Warbler species:

MYRTLE YELLOW-RUMPED GROUP = 2 subspecies:

1) Dendroica coronata coronata = Myrtle (Yellow-Rumped) Warbler; 2) D.c. hooveri = Hoover's (Yellow-Rumped) Warbler (not recognized by Jon Dunn and Kimball Garrett's 1997 "Warbler" Field Guide, but this subspecies is acknowledged within the Birds of North American Online). (See http://bna.birds.cornell.edu/bna/species/376/articles/systematics if you have a subscription to this $40 per year service; if you need to join, please go to
http://bna.birds.cornell.edu)

AUDUBON'S YELLOW-RUMPED GROUP = 3 subspecies:
(#3-#5 among the five subspecies in the species)

3) D.c. auduboni = Audubon's (Yellow-Rumped) Warbler;
4) D.c. nigrifrons = Northwest Mexican Black-fronted (Yellow-Rumped) Warbler) (non-migratory); and
5) D.c. goldmani = Guatemalan Goldman's (Yellow-Rumped Warbler) (non-migratory).

Such an update in the taxonomy of Yellow-Rumped means
my earlier post from 2009 on this “wood-warbler” blog is now outdated.

Previously, Jon Dunn & Kimball Garrett split Yellow-Rumped into six subspecies: two subpecies formed the Myrtle Yellow-Rumped Warbler and four subspecies living in different geographical areas qualified within the Audubon's group.

Got all that? Your eyes are plowing through the snow drifts of words, above, but have not yet resorted to wearing snow tires?

If so, then consider one final thought related to Yellow-Rumps:

It's the word "impressive" -- as in suggesting this term is even too modest a way to describe the Yellow-Rump’s amazing BraveHeart survival ability, given its presence throughout the winter during many years within higher latitudes (i.e., upper Midwest and southern New England) where chilly winters prevail.

On the other hand, where I live in the mild Bay Area of northern California, the over-wintering bar is not as high for Yellow-Rumps whose presence during the non-breeding season includes both visiting populations of Audubon's and Myrtle's. Here, they are a common to abundant sight amid various habitats, including Eucalyptus, Monterey Cypress, and Monterey Pine groves within urban, suburban, and rural habitats.

Talented, refined “birding by ear” listeners are able to determine the Myrtle vs. Audubon's subspecies by each's diagnostic, yet sound-alike call note — a challenging feat, to say the least. In fact, I opine that the difficulty of distinguishing the two subspecies from one another by call is for many birders on par with identifying by sight a week-old Twinkie from one that has aged for two weeks. Not too easy, correct? Notice that I’m mentioning “call note” here because the songs of Myrtle vs. Audubon's are indistinguishable, according to Dunn & Garrett.

As for the multiple drawings devoted to this species on the color plates featured in Dunn and Garrett's Warbler field guide (as drawn by the fine artist and birder Tom Schultz), it exhibits excellent views of the diagnostic field marks germane to each subspecies.

In short, to tell them apart, note how Myrtle is the only subspecies of the four adults to exhibit white in the throat compared to the faint to brilliant yellow sheen seen in the other three subspecies: Audubon's, Black-fronted, and Goldman's.

6 comments:

Anonymous said...

Great post. Thanks.

Now I get it.

Jamie S.

Urban Wild said...
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Urban Wild said...

Thanks for this wonderful clarification. I had no idea there were other ssp. besides Audubon's and Myrtle's. We get the audubon's version here in Los Angeles from about mid-October through mid-April. They are old, familiar friends each fall. I have used the Dunn-Garrett guide for years and still find it very useful, but it would be nice if they did an updated version someday--given that neither one of them is getting any younger!

Anonymous said...

Urban Wild: Yes, an update would be nice for Dunn & Garrett, BUT I also know that in lieu of writing an update, they are busy doing excellent work on behalf of the bird world in terms of going to conferences, for example, and educating birders/professionals.

I consider myself lucky that I will soon attend the Central Valley Birding Symposium in Stockton, CA (11/23-11/25/09) where Jon Dunn will present. Regards, Daniel Edelstein

Anonymous said...
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Anonymous said...

A question: if there is a group referred to as wood-warblers, it suggests at least one other group of warblers exists. What is/are that/those other group(s)?

Old world and new world both seem to have a Wood-warbler group although with different genus name? What is the commonality?
PW - Alaska