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AUDUBON'S "EXTRA" WARBLER

Within the world of birding exists a semi-competitive sport known as "listing," in which individual birders try to see how many different species they can sight and add to their list(s). Most birders keep "life lists" (all the species they've ever seen), "year lists" (for species seen in a particular 12-month period), and "country, state, or county lists" (species encountered in a specific geographic entity). There are all sorts of variations on the theme--we personally have lists of all the birds we've ever photographed or banded--and most birders have "yard lists" for species seen close to home. At Hilton Pond Center, our yard list stands at 166 birds observed on or over the property since 1982--plus a Barn Owl feather we found one morning, undoubtedly after its previous owner flew through the night before. Oddly, the number of species on a birder's "life list" could go up or down even AFTER the birder dies--mostly because of actions by the American Ornithologists' Union (AOU), which looks at bird taxonomy and provides the "official" list of bird species in North America. Birders await--with a mixture of excitement and dread--each new edition of the AOU checklist, hopeful a particular bird with a wide geographic range has been determined to actually be more than one species; i.e., it is "split" into two different species. Such action instantly adds a new species to the birder's life list, but rue the day when genetic work or extensive field studies reveal two or more old species must instead be "lumped" into one, costing the birder a tally on the life list. All this lumping and splitting isn't a new phenomenon for bird enthusiasts, as John James Audubon discovered in the early 19th century when he had to delete an "extra" warbler from his life list of North American birds.

All text & photos © Hilton Pond Center

We were reminded of Audubon's list loss this week when a rather nondescript warbler hit our nets and we brought it in for banding. In Audubon's words--and as rendered in his Elephant Folio painting (above left)--this newly captured bird was "greenish-olive above, light dull yellow below, with a less extended white patch on the wing, the white on the tail [spots] unconspicuous (right)." We might add our bird--and the one in Audubon's painting--had a prominent white eyeline and an incomplete eye ring beneath the eye (see photo just above). Audubon collected several specimens of this bird in spring migration and referred to it as the "Pine Swamp Warbler, Sylvia sphagnosa"--seemingly a good species to add to his life list.

At about the same time Audubon observed this migratory Pine Swamp Warbler, he collected another that was much more colorful and whose name was far more descriptive: "Black-throated Blue Warbler, Sylvia canadensis"--yet another member of the Wood Warbler Family (Parulidae) for Audubon's life list. Audubon painted a spectacular male black-throated blue perched on Red Columbine (left)--an appropriate vignette because this flower blooms in early spring about when the Neotropical warber returns from its winter range in the Bahamas and Greater Antilles to its breeding grounds--primarily the Appalachians, New England, and southeastern Canada. Breeding is rare but confirmed in Upstate South Carolina and occurs regularly in North Carolina's mountains. (As an aside, we should point out the columbine is a herbaceous plant--not woody as it seems to be in Audubon's illustration above.) Despite his beautiful, scientifically accurate depiction of the Black-throated Blue Warbler male, Audubon undoubtedly was perturbed when he was unable to find a female of the species to study and depict along with her mate. Little did the great naturalist suspect he already had already painted what could have been TWO female black-throated blues.

In one of the first recorded faux pas of North American ornithology, the continent's two foremost bird painters of the 19th century--Audubon and his predecessor, Alexander Wilson--failed to realize the so-called Pine Swamp Warbler was actually a female (or perhaps juvenile) Black-throated Blue Warbler. In defense of Wilson and Audubon, sexual dimorphism in the black-throated blue is extensive; not many of our North American species show such dramatic external differences. Other than size and shape, about the only obvious field mark the sexes have in common is a white spot at the base of their outermost primary wing feathers. The spot is large and always present in males and usually shows to some degree in the female (above and below), but this common characteristic didn't seem to click with the two pioneering ornithologists.

True to his ego, Audubon blamed his own mistake on others who incorrectly classified the female black-throated blue as Sylvia pusilla. In Audubon's words: "The birds represented in Plate 148 of my large edition [the Elephant Folio of Birds of North America] as Sylvia sphagnosa are the young of the Black-throated Blue Warbler, the female of which resembles them so much that I looked upon it as of a species distinct from the male [below]. I have no doubt that this error originated with Wilson, who has been followed by all our writers. Now, however, the Sylvia or Sylvia sphagnosa of Bonaparte [another early ornithologist], which he altered from Wilson's S. pusilla, must be erased from our Fauna." Scratch one species from Audubon's life list.

At Hilton Pond Center we have captured migrant Black-throated Blue Warblers from 24 April to 1 June in spring migration, and from 1 September through 26 October in autumn--typical dates for the South Carolina Piedmont. The species is sixth in abundance on the Center's list of Parulids; we've banded 147 since 1982--enough to keep us from repeating the identification mistake of Wilson and Audubon.

Thanks to modern field guides, birders are no longer misled by the significant differences between male and female Black-throated Blue Warblers like those we catch and band at Hilton Pond Center. Now classified as Dendroica caerulescens, this once-confusing bird counts only once on anyone's list, so John James Audubon's "Pine Swamp Warbler" is just an "extra" species that--after painting an "unnecessary" plate for his Elephant Folio--he correctly chose to delete from his lifetime tally.

All text & photos © Hilton Pond Center