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 http://www.aou.org/checklist/north/full.php).

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

Stay tuned.

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.

Warbler Guy: Do warblers migrate over the ocean or was this bird (below photo) confused and lost?

Thanks for the question, Kevin.

Here's my answer, though it's a simplified one to your question that deserves more ink than this digital retorte provides.

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Given your interesting photo of the Black-Throated Gray Warbler that landed on your boat’s deck while amid the Pacific Ocean, it’s 100% certain that your unfortunate friend is lost and wayward from its normal southern migration route. More exact, no wood-warbler species on the West Coast have yet been discovered to migrate to non-breeding/wintering grounds via an oceanic route.

On the West Coast, only disoriented and/or wind blown wood-warblers show up on offshore islands, such as those often seen by bird banders/researchers stationed at the central California chain of islands called the Farallones. Here, banders have captured in their nets various species of so-called eastern wood-warblers. Others, like the Black-Throated Gray in the photo, below, are wayward sojourners desperate for a wayside to rest upon while fighting to survive in a pelagic habitat that offers no food resources.

Unfortunately, the vast majority of wood-warblers seen resting on boat decks, buoys, and rip-rap along coastal and deep water habitats typically are hatch year birds. Most will either perish while traveling over the Pacific ocean before reaching island refugia such as the Farallones or incur high mortality after being set free by banders that discover them. Some researchers suggest eastern wood-warblers found on the West Coast (including Farallone Island individuals") are inherently "dyslexic" in the sense they do not have the orientation design necessary to complete the classic migration routes that their brethren successfully negotiate each spring and autumn on their north and south peregrinations.

Beyond the West Coast, trans-oceanic migration by songbirds is rare -- and, in the wood-warblers seen in N. America north of Mexico, it is only documented to occur in a few species.

One of them, for example, the Blackpoll is known to contain populations that in autumn perform the high-octane feat of an ocean migration route that totals more than 2,150 miles (NE USA/Maritime Provinces to northern South America).

How do researchers know the Blackpoll performs such a magician's stunt annually?

It's because bird bander's in Bermuda (an island east-southeast of the southeastern USA) band birds in the autumn, and, thereby, sometimes catch Blackpoll in their nets. Evidently, Bermuda is in line with the route over which Blackpoll travel during their southbound migration and this small island serves as a stopover wayside area for Blackpoll that wish to stop and "refuel" before leaving to migrate south again at night.

High-octane is an apt description of the Blackpoll's Herculean task because many leave their "staging" grounds en masse with other Blackpolls and fly en route together as heavyweight butterballs while weighing as much as 26 grams (nearly an ounce) at the beginning of their air treks.

By the end of the Blackpolls' long-distance trip, however, they have been documented to have lost half their starting weights. Emaciated and Twiggy-Thin Blackpoll, therefore, in some cases, are known to digest their muscle to serve as a last resort energy source.

While winging south, researchers have figured Blackpolls burn .08 grams per hour during their three to four days of travel, a process that is a non-stop direct flight, if the Blackpoll does not stop at island refugia such as Bermuda. In comparison, such a weight loss program for club members and gym rats on two legs would mean a 20-pound or more evaporation of girth per day (for the typical weight of 6' tall male or 5'6" female).

Now there's a weight loss program that would attract headlines and lead to a manic panic for (I imagine) a best-selling book titled: "Migrating With a TailWind To A Fat-Free Lifestyle." :-)

Warbler Guy: To help me with my warbler identification skills, can you tell me which warblers look the same year-round and don’t seem to become drab?

Among the 52 wood-warbler species typically seen annually in North America (north of Mexico), only 11 wear their flashy, bright, high-definition (alternate) plumage year-round. The vast majority — the other 41 species — undergo a molt before they migrate, so the males turn drab and less colorful after the breeding season.

Which11 warbler species look similar year-round?:
According to two sources I carefully checked — “Field Guide to Warblers,” (Jon Dunn & Kimball Garrett) and “Identification Guide to North American Birds (Part 1)” (Peter Pyle) — the answer is Golden-Winged, Yellow-Throated, Pine, Prothonotary, Worm-Eating, Swainson’s, Ovenbird, Louisiana Waterthrush, Red-Faced, Painted, and Yellow-Breasted Chat.

Expanding upon the basic facts presented above, most North American birds replace all their feathers during a complete molt that occurs in late summer or fall. The new feathers that develop before the birds leave on migration create an appearance that will be present throughout the fall and into winter. The technical word for this appearance is “basic plumage” because it usually persists longer throughout the year than the breeding (or alternate) plumage stage.

As indicated above, the majority of wood-warblers undergo a second molt that may occur progressively throughout the winter on the non-breeding grounds or as a more rapid molt before they leave to migrate north. This molt is called the peralternate molt and results in alternate plumage (or breeding plumage). In simple terms, think of this molt as providing birds the ability to “alter” their appearance to be colorfully attractive for the breeding season.

Of course, it is the males that most benefit from shedding their basic, non-breeding, drab (basic) plumage and transform into a brighter façade. That’s because the females pick their male partners when nesting occurs on the breeding grounds, a process that begins after migrating males arrive and preceded by the prealternate molt that occurred for them in their non-breeding grounds.

If you’re lucky enough to see warblers performing breeding and courtship displays, then you’ll see first-hand how the pretty males attempt to catch the eye of their female suitors (that are typically slightly more drab in appearance). Courtship poses include various wing gyrations and diving/hovering displays, among other behaviors.

As a closing note, it’s a good idea to remember that not all prealternate molts result in a prettier, more colorful appearance among male birds. Consider three ptarmigan species in the western USA and Alaska that molt from a majestic snow white basic plumage appearance to a more mottled, camouflaged expression that matches their tundra (and other habitat) surroundings and is, thus, more suitable for the ptarmigans’ survival in their summer environs.

Wisconsin Kirtland's Warbler Nesting Update

(Above, Kirtland’s warbler male at a new Adams County site, June 12 2009.
Photo by USFWS; Joel Trick)

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Want to know how many Kirtland's Warbler individuals were seen in WI this past 2009 breeding season?

Which counties?

How the Kirtland's third consecutive year of documented nesting in the state suggests this federally endangered songbird is now an annual nester in Wisconsin? -- in addition to, of course, nesting yearly in at least 12 Michigan counties (where at least 1,803 individuals were confirmed in 2009).

If so, please feel free to visit the following WI DNR link:

http://www.fws.gov/midwest/GreenBay/kiwa/2009Summary.html

Warbler Guy, do you know when the warblers begin their autumn migration?

Good question, Neal in the “Midwest,” per your question in the “comments” section of the 8/7/09 article I authored here.

Wood-warbler migration actually begins in the summer by July or August for many species, if you also add in their initial travel in various directions away from breeding grounds (i.e., a behavior that is called “dispersal”). That is to say, unlike the more direct, dawdle-free behavior wood-warblers exhibit as they travel north on favorable tail-winds during spring migration, their post-breeding migration south is often a stuttering, stop-and-start, protracted itinerary.

Weather patterns in August through early October are a principal factor as to when many bird species (including wood-warblers) initiate migration and, subsequently, how far they travel on each segment of their southward night-time journeys. With north and northwest winds at their backs, wood-warblers may travel as many as 100 to 150 miles during a night’s journey.

Then again, feeding layovers for one or more days may occur where wood-warblers find abundant food resources. Likewise, binge eating sessions may be required when their body fat reserves deplete. Excess rain and unfavorable wind conditions also force wood-warblers into holding patterns until conditions improve.

Given the background information mentioned above, note it’s merely a brief and general summary of autumn bird migration patterns. More exact, consider that post-breeding season migration is an obligatory behavior most wood-warblers perform following dispersal from their breeding grounds.

Greeting the season’s initial freezing low temperatures, wood-warblers rudely discover their primary food source — insects, during the breeding season — rapidly disappear from the landscape. Consequently, migration emerges as an imperative survival behavior.

How many warblers migrate? For the majority of North America’s (north of Mexico) 52 annually present warbler species, their journeys begin by mid- to late summer (at the earliest) and no later than early to late autumn. So, for example, “early birds” such Yellow Warbler may begin dispersing/migrating in July, while other populations of the same species may wait until early October to leave for southern latitudes where they’ll spend the non-breeding season.

Other late summer, early-to-leave migrants include Tennessee Warbler, American Redstart, and Louisiana Waterthrush, all of which begin dispersing from northern breeding territories in July. True, uninterrupted migration toward “winter” habitat may not occur for these species (and many other North American wood-warblers) until beyond July and as late as October (and, more rarely, November and December) for some populations.

Only a handful of warbler species either do not migrate or remain annually (or periodically) throughout the winter in higher latitudes as far north as southern Wisconsin, Ohio, New York, and some New England states. This select club of bravehearts includes at least one subspecies of the Common Yellowthroat (among its 13 subspecies that live in North America), Yellow-Rumped Warbler, Palm Warbler, Orange-Crowned Warbler, and Yellow-Breasted Chat.

Which wood-warbler is the earliest to leave its breeding grounds? A leading contender is a subspecies of Orange-Crowned Warbler populations that breeds on the West Coast. Where it breeds in the San Francisco Bay Area, for example, Orange-Crowned often leave its dry and dormant environs by June, retreating to foothill and Sierra Madre mountainous habitat as intermediary “staging ground” habitats where cooler and moister conditions dominate and, thus, host abundant insect food resources.

For more details about the typical annual dates when each North American breeding wood-warbler disperses and/or migrates, see Jon Dunn and Kimball Garrett’s “Warbler” field guide (A list of the best warbler field guides and resources appears in a 10/21/08 article on this blog, so please feel free to scroll down the page and click multiple times on "older posts" to find it.).

More simplified information relating to autumn migration times for most USA-breeding wood-warbler species appears in a “Warbler Tips ID Chart” at my Web site: www.warblerwatch.com (After arriving at this site’s home page, click on the button title “Warbler Tips ID Chart.”)

Can you please share the answers to your latest quizzes?

Yes, Jeremy S. (Tucson, AZ). Here’s the answers:

1. Can you name the two hybrid forms that sometimes result when Golden-Winged and Blue-Winged Warbler mate?

Answer:

Lawrence’s and Brewster’s

2. Can you name two wood-warbler species that are breeding endemics to one USA state?

Tropical Parula and Golden-Cheeked

3. On the West Coast, which wood-warbler is one of the earliest dispersing species after nesting?

Answer:

Orange-Crowned Warbler, given many disperse and/or migrate from the Bay Area by June.

4. Among the species listed in the 5/29/09 article, which one is considered extinct?

Answer:

Bachman’s Warbler

5. Common Yellowthroat was often previously named differently in many field guides as XXXXXX Yellowthroat?

Answer:

Maryland Yellowthroat

6. Beyond Michigan's breeding population, where else do researchers believe the Kirtland's Warbler regularly to periodically breeds?

Answer:

Wisconsin (as only one documented nest has been found in Ontario during the 1945 breeding season), while Kirtland’s has bred from 2007 through 2009 in Wisconsin.

7. Which common wood-warbler's breeding range is split into an eastern and western subspecies breeding population?

Answer:

Nashville Warbler, as its two USA subspecies are split into separated (allopatric) populations while nine Yellow Warbler species occur in the USA among the 43 total subspecies within North, Central and South America.