Annotated checklist and data resource
text © Don Roberson
photos copyrighted by photographer(s) credited
all photos taken in Monterey County, California
Mystery Dendroica warbler
The following photos were taken 10 Sep 2005 at Carmel R. mouth., Monterey Co., California; all © Don Roberson.
This bird had been initially reported on 7 Sep 2005, in the same locale, and variously called a Blackpoll, a Yellow, and an 'odd bird'
What do you make of this warbler (below)? On first glimpse in the willow canopy it looks to be a yellowish warbler with wingbars, a white vent, prominent white tail spots, obscure breast streaks, and pale legs (top left, below). Standard Blackpoll, no? Then one gets a different perspective (top right, below) and it looks like a Yellow Warbler: big complete eyering, yellow color all over breast and back, and blank face. Huh? So we have a Yellow Warbler with wingbars and tail spots . . . what gives?

So here's good side view (above). The back and flanks are washed yellow-olive and obscurely streaked. The tertials are blackish with broad white edges; the primaries are thinly tipped with white. The upperpart color is rather bright. The tail is short but the primary projection long. This all suggests Bay-breasted. But the greater coverts seem odd: the 'wingbar' (white tips to feathers) is rather obscure as outer edge of every feather has a whitish to yellowish edge. More like Yellow?

Let's look at that face again (below). Sometimes the complete and yellowish eyering is prominent (below left); at other times lighting emphasizes a dusky loral area (below right). But the bird lacks the well-defined transocular line associated with Blackpoll and Bay-breasted Warblers. The rather lemony-yellow throat and breast is fine for Yellow Warbler and also okay for Bay-breasted. Note (below left) the flesh-colored feet in the light, but brownish-looking legs in the shadow.

From below (above left) the bird is mostly yellow (like Yellow Warbler) but looks short-tailed and long-winged. What of the tail spots (above right)? They were decidedly white (below)  and cover much of the inner web of the outer rectrix (above right). All the rectrices are a bit worn and pointed, typical of HY birds. The amount of white does not really seem consistent with drawings of Blackpoll or Bay-breasted tail spots in Pyle (1997) but could be consistent with a Yellow Warbler tail pattern if the color were yellow instead of white.
So we are left with a Yellow Warbler with apparent wingbars (above left) and contrasting white undtertail coverts and white tail spots (above right).  Let's review the possibilities:
  • Yellow Warbler: face pattern and overall color are just fine; size and bill and even the brief 'chip' heard were consistent. It was the size and basic shape of a typical Yellow nearby. Yellow edgings to secondaries is typical. But how to explain white wingbars, white undertail coverts, and white tail spots?
  • Blackpoll Warbler: the obscure streaking to breast and back is good, as are the brownish legs with flesh-cololed feet. But surely they can't have a facial pattern without a transocular line and a cheek patch?
  • Pine Warbler: although some who saw the bird and looked at Sibley (2000) suggested this species was the closest match, it seems entirely ruled out on facial pattern, leg color, habitat, shape (e.g., long primary extension), and the white tips to primaries (per Dunn & Garrett 1997)
  • Bay-breasted Warbler: although said to have the plainest facial pattern of the 'Baypoll' group, surely it would have some eyestripe? Also the leg color seems atypical (although perhaps within range; Dunn & Garrett 1997) but the nape did not seem green enough, the vent buffy enough, nor the back streaks crisp enough. Whitney (1983) says 10-30% of fall Bay-breasteds lack bay to the flanks; these are first-fall females. I think the specific shape of the tail spots do not fit well, though. This was my first tentative i.d. but it does not now seem right.
  • Hybrid? One would think that a hybrid would include Yellow Warbler as one parent. Per Dunn & Garret (1997), the one 'possible' claimed hybrid with Yellow was a Black-throated Blue. Nothing with wingbars.
So is this just a Yellow Warbler with wingbars and white vent & tail spots?
Literature cited:
  • Dunn, J.L,, and K.L. Garrett. 1997. A Field Guide to the Warblers of North America. Houghton Mifflin, Boston.
  • Pyle, P. 1997. Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA.
  • Sibley, D.A. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.
  • Whitney, B. 1983. Bay-breasted, Blackpoll, and Pine Warblers in fall plumage. Birding 15: 219-222.

Use these links to reach other portions of the Monterey County list:

Part 1: Waterfowl through Grebes
Part 2: Albatrosses through Frigatebirds
Part 3: Herons through Cranes
Part 4: Plovers through Sandpipers
Part 5: Jaegers through Alcids
Part 6: Doves through Woodpeckers
Part 7: Flycatchers through Larks
Part 8: Swallows through Pipits
Part 9: Waxwings through Warblers
Part 10: Tanagers through Sparrows
Part 11: Grosbeaks through Finches
or just the plain Checklist (no annotations)
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Page created 10 Sep 2005