Wednesday, October 21, 2009

Hey, Mr. Warbler Guy: Is a Yellow-Breasted Chat truly a wood-warbler? C’mon, they don’t look like one, act like one, or sound like one.

Answer: Good question, Rob, in Cordelia, CA.

At seven inches from bill tip to tail tip, the Yellow-Breasted Chat (YBCH) is EASILY our largest North American wood-warbler family member. All the other warblers in our area range from 4.25 to 5.5 inches in length. Equally vexing, unlike YBCH, most other wood-warblers have an insect-catching small bill. Consequently, seeing a YBCH’s oversized one — it looks more like a tanager’s in shape and size — leaves you scratching your head.

So does hearing its Northern Mockingbird/Brown Thrasher-like song. Even the YBCH’s skulking, secretive behavior is somewhat strange for a wood-warbler, given many (especially among the 27 Dendroica genus members in North America north of Mexico) are extroverts in fast-forward mode during the breeding season while displaying “hover and glean” foraging behavior in search of insects amidst the tips of branches.

So why is a YBCH considered a wood-warbler? Primarily because researchers use more than birds’ songs, their behavior, their skeletal structure, and their general appearance to define a species (as well as the genera, families and orders of birds that constitute the 9,800 or so species in the world). They also employ blood analysis (i.e., DNA/DNA hybridization techniques) techniques. All of these aforementioned distinguishing techniques form the “Phylogenetic Species Concept” that is broadly accepted by most taxonomical scientists (but only SOME biologists) as an accurate way to determine a species.

Of course, molecular analysis of blood is a somewhat recent development technique for distinguishing birds at the species level. Hearken to pre-DNA analysis, and you stumble upon the studies of one E. Eisenmann. In1962, he called into question the then generally accepted placement of the YBCH in the wood-warblers by pointing out how it is missing jaw muscle, thereby suggesting an affinity with tanagers (Thraupidae family). Eisenmann also argued that the YBCH’s hyoid apparatus (a specialized system of bones and muscles within the avian tongue) differs from that of design present in many songbirds. No matter. Eisenmann lost his tug of war with other experts. Various conscientious objectors in the birding community have similarly raised their voice (and ire) to question the inclusion of YBCH in the wood-warbler family.

Adding fuel to the debate is the American Ornithological Union's checklist of birds where an you an asterisk appears after YBCH's name, denoting that this species is "probably misplaced in the current phylogenetic listing, but data indicating proper placement are not yet available" (see

Nonetheless, YBCH holds tight. It officially remains a wood-warbler.

Stay tuned.

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:


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 if you have a subscription to this $40 per year service; if you need to join, please go to

(#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.