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Comment: Some Illustrations of the Townsend's Bunting
Comment: Some Illustrations of the Townsend's Bunting
Comment: Some Illustrations of the Townsend's Bunting
Mathew Louis
June 16, 2015
Having previously written for Wildbirds Broadcasting a recent piece (June 4, "The Identity of Townsend's Bunting"), I have examined a few more sources which include illustrations of the subject and will comment, these points contributing to the discussion as well as reinforcing my arguments. Four additional publications, all published or cited in recent years relating to the Townsend's Bunting, deserve consideration.
**** Audubon, The Watercolors for The Birds of America (Blaugrund & Stebbins, eds.), 1993. This includes the two original watercolor portraits Audubon prepared before creating the plate for Emberiza townsendi. One is a cut-out applied to a page including other figured birds, the specimen posed much as it would appear in the final product. The other is a study of the type in three poses; the lower figure shows a crown with what appear to be scattered streaks. (As I noted in my aforementioned piece, the Lark Bunting's crown has scattered streaking whereas immature Dickcissels reveal even rows of streaks.) Also see Audubon's Aviary (Olson, ed., 2012).
Relating to the discussion in the next work I cite, it is important to stress that Audubon painted his from a fresh type, this a bird with no yellow coloration, especially on the supercilium and malar areas (which are white in his bird), thus removing the possibility that the Townsend's Bunting type in its original state may have had yellow feathers which later faded.
Links with image examples of these:
audubonart.com/galleries/watercolors/awc_plate-13a-townsends-bunting/
**** "Audubon's Mystery Birds." Kenneth Parkes in Natural History (94: 92).
Parkes discusses the type specimen of the Townsend's Bunting in the U.S. National Museum and argues that it is an aberrantly-colored Dickcissel. Having read it, I find that this argument has some weight, but overall it is not supportable. What Parkes is describing is called a schizochroism, a condition of abnormal plumage color as a result of a lack of a certain pigment; hence in this case Parkes is arguing that that pigment is the Dickcissel's yellow, resulting, in this case, in a more gray-colored bird. Schizochroism yields a different color than normal. Given that I am arguing that the Townsend's is a Dickcissel x Lark Bunting hybird, an explanation may truly concern the colors of the Lark Bunting, a bird in which the male in breeding plumage is a stunning black with white wing panels; it is the blackest of the North American sparrows.
I would describe the Townsend's type differently. As the hybridization preserves characters of both species, I suspect that a cross will result in a hybrid with an increase of eumelanin resulting in a darker bird--the "common" melanistic or eumelanic trait, but a phenomenon which does not force questions, which I propose here, of inconsistency that an aberrant coloration argument produces. ("[I]n a eumelanistic bird, the amount of phaeomelanin remains normal but through the increase of eumelanin concentration, the phaeomelanin will not or be hardly visible." Dutch Birding, 28: 88.) Parkes' singles the Dickcissel's yellow pigment above its other colors, and this is problematic as the Townsend's type does not consistently show the "schizochroism" in areas of its plumage where it would be expected. A schizochroism can, from my understanding, be understood by analogy: the plate [39] of Carbo perspicillatus in Extinct Birds (Rothschild, 1907). In this plate, by John Gerrard Keulemans, the cormorant's orbital ring was incorrectly colored red, the same color as its gular skin. In context, the white part was substituted, and in a schizochroism, an analogously similar switch of pigment should result. All yellow feathers might become white or some other color, or all green areas might become blue (in a case of an axanthic schizochroism), but other patterns and colors, no matter how intricate, would be unaffected. While the Townsend's type has a gray breast and underparts, making it feasible as to how Parkes arrived at such a judgment, its supercilium is unequivocally white. Even in non-breeding plumage and immature plumages, a Dickcissel almost always shows a yellow supercilium, usually with a yellow mark on the malar and, infrequently, yellow along the center area of the throat. Thus, there is an inconsistent correspondence of yellow plumage characters in the Dickcissel appearing in the mystery bird as either gray or white, not just one color. It is not unexpected to find in an aberrant plumage some retention of the typical colorations, but I find it irreconcilable to argue that this pattern in the Townsend's would emerge from a schizochroism, given that so much of the head is gray in color (gray the color replacing the yellow of its breast) but not the superciliary mark nor the malar.
Further, the gray on the underparts is much more uniform and extensive in both examples (the Townsend's and the mystery Ontario bird); a schizochroism should only affect a certain pigment, not affect coloration of feathers peripheral to that part. As my comments will further explain, a schizochroism argument applied to the mystery Ontario bird does not hold either. (Parkes also incorrectly described the Townsend's Bunting type as a female).
The question of another aberrant plumage form, a non-phaeomelanin schizochroism, is worth mention, though this argument cannot be supported. In a melanistic bird, the phaeomelanin is preserved, and if it were not then the Townsend's Bunting might show a subtly darker tone in its brown-colored characters, the wings, back, and tail. Hein van Grouw, quoted above in Dutch Birding, also writes: "[w]hen phaeomelanin is absent (grey), only black-grey and dark brown colours will be visible, the red-brown to yellowish-cream colours having disappeared." Given that the Townsend's has such remarkably inconsistent coloration with what a true aberration would be expected to produce, it would, again, be difficult to see how some yellow areas of an abnormal Dickcissel would be white (superciliary mark, malar) while others dark gray (breast), or while some non-yellow areas are excessively darker (flanks, sides of breast), if this was a non-phaeomelanin schizochroism.
One review of this case (Holt; Cassinia, 70: 24) also draws attention to a source which characterizes male North American Cardinalinae as having a protracted development, and that the Townsend's might be such a case of an abnormal immature plumage. It would be difficult to consider how this phenomenon would be so rare when if, as the author suggests, it is understood among all the North American species of the group. Delayed plumage maturation results in a supposedly gradient variation among males, which would appear in plumages resembling both sexes. To construe the possibility of the same in the Dickcissel, resulting in an aberration like the Townsend's, is worth pondering, but I find it problematical. The Townsend's Bunting does not actually reveal any obvious immature or female-type Dickcissel plumage characters despite Parkes' incorrectly describing the type as a female. Substantiating this argument would require a comparative examination of materials which show variation among immature male Dickcissels.
The Ontario bird does faintly show yellow along its superciliary mark, and shows a small spot of yellow along the malar and a faint mark just below the breast, but even a "partial schizochroism" argument is not supportable as the latter yellow mark begs question as to why the whole of the breast is not dark gray, as well as the question of the excessive amount of dark gray appearing not just on the breast but, closely similar to the Townsend's Bunting, also on the flanks and sides of the neck--areas that should not be affected, as they are not normally yellow in a Dickcissel. The yellow of a typical Dickcissel's underparts is concentrated on the breast, and along the sides of the breast and flanks there is often just a weak yellow blush. In this case, and no less in the case of the Townsend's Bunting, the gray is uniform and extensive across the breast and sides. I am at a loss to understand how this would be a schizochroism given the heavy saturation of the gray on the sides of the breast where the corresponding "affected" yellow color is only weakly present in the feathering in that part. Even more untenable is how the gray leads from the breast to the sides of the neck and face and the malar pattern--this is not a consistent substitution due to the gray concealing much of the white of the sides of the neck that would appear in a typical Dickcissel (leading from the throat, as in the image in Harrison and Greensmith (Birds of the World, Dorling Kindersley, p. 339)). Immature and female plumages, both, in typical birds also show this character. Females usually show a white or pale area at the trailing edge of the malar mark, and males have a throat with a black center. Regardless of the sex of the Ontario bird, both white and yellow feathers are affected by its aberrant condition, and should it have proven be an adult male, its black should also have been affected. Thus, its plumage more likely suggests a melanism from hybridization rather than a schizochroism.
The bird that was photographed in Prince Edward Point Wildlife Area was not sexed. It is difficult to tell if that bird, due to its having some characters markedly different from the Townsend's Bunting, would be the "typical" female hybrid, or another male hybrid with different characters. I tend to favor the second possibility (and suggested it previously) that this is also a male, but it is largely my speculation. As I have noted for the Townsend's, there is likewise nothing to show of female characters of the Dickcissel in this particular bird, and its heavy gray tones suggest a darker, more melanistic individual--the melanism here greater and tending more towards conveying a male Lark Bunting association than in the Townsend's. The black/white wing-coverts of the Ontario bird could suggest an immature male, or, possibly, a female, but it is not readily obvious which sex that character suggests of the Lark Bunting parent. Overall, a hybrid with excessive melanism is represented in both mystery birds. Characters of hybridization are present in both, and due to their Lark Bunting parents possessing the melanistic trait in their makeup, that trait is evidently preserved, in a limited way, in both cases.
**** "Townsend's Bunting in Ontario?" Denis Lepage in Birding (46(4): 30--32 (July/Aug. 2014))
A discussion on the bird photographed by Kyle Blaney on May 14, 2014 is given. The case is based on observation and photographs; the bird was only seen briefly, with nothing to interpret from its behavior or flight pattern, nor was it vocal. Lepage notes that this individual was considered by some to be a hybrid of various species, and he names the Bobolink Dolichonyx oryzivorus, House Sparrow Passer domesticus, and the Sagebrush Sparrow Amphispiza [belli] nevadensis as examples suggested of the identity of the parent. The Sagebrush Sparrow (or Sage Sparrow) is given particular consideration, and an image of one is used for comparison. I do not believe that this Ontario bird adequately, if even closely, suggests characters of the Bobolink or House Sparrow which would approach challenging a Lark Bunting hybird argument.
Likewise, a presumed Sagebrush Sparrow hybrid is not a possibility either. The Sagebrush Sparrow breeds in a limited distribution in the western U.S. states, and, unlike the Dickcissel or Lark Bunting, does not occur in great numbers at any one time to make a hybrid pairing event a likelihood. Taking both the forms belli and nevadensis together (as they were long considered to be representative of a single species, "Sage Sparrow"), the Sage Sparrow's breeding distribution is completely allopatric to the Dickcissel's, and the only area of overlap in non-breeding occurrence (Sibley Field Guide to Birds of Western North America) is an isolated section of southeastern New Mexico, south to Texas and the northern extremes of Chihuahua and Coahuila, where the Dickcissel only occurs as a passing migrant. Measurements (males unless noted) given on page 270 from Ridgway (cited in previous) of a series nevadensis Sage Sparrow are as follows:
Length: 139.70--157.48 (149.61); female 137.16--157.48 (146.81)
Wing: 77.47--81.28
Tail: 70.61--78.49 (74.68); female 67.31--75.69 (71.37)
Exposed culmen: 9.40--10.41 (10.16); female 9.40--10.41 (9.91)
Depth of bill at base: 5.08--5.84; female 5.33--5.84
Tarsus: 20.83--22.61
Middle toe: 12.70--14.73
Ratio of average female exposed culmen to average female length: 1: 14.81
Tail measurements of the other two species in question are also quoted:
Spiza americana
Tail: male 55.12--61.47 (58.17); female 50.04--55.12 (52.07)
Calamospiza melanocorys
Tail: male 65.53--71.12 (68.58), female (60.45--68.58)
At once it is clear that the Sage Sparrow has a remarkably smaller beak than any of the forms in consideration (compare with measurements in previous essay). Beak depth as well as beak length in relation to overall size represent a departure from the measurements and proportions of the Townsend's Bunting, Dickcissel, and Lark Bunting. While the Sage Sparrow's length is close to the Townsend's, its tail is nearly half of that length. Ratios to one of the average female tail to average female length (nevadensis Sage Sparrow: 2.06, Lark Bunting: 2.29, Townsend's Bunting: 2.73, Dickcissel: 2.75) further demonstrate that its proportions remove it from consideration. Its beak is of a uniform blackish color, not at all like the birds in questions. As I previously stressed that the Townsend's Bunting and the Ontario bird, despite their differences, are appreciably similar in appearance to be treated together ("what holds in the identity in the original Townsend's Bunting holds for this more recent example, one and the same"), the arguments derived from a comparison of specimens may have further applicability to this photographed bird. Though it may be larger (or even smaller) than the Townsend's, I feel that the arguments may, in part, especially hold with regards to proportion.
**** Peterson, R. T. (Peterson & Peterson (et al)), Field Guide to the Birds of Eastern and Central North America (5th edn. (2002)), pp. 318--319. Both the Dickcissel and the Lark Bunting appear together on the same page, placed under the fitting heading, "Miscellaneous Finchlike Birds." Peterson had categorized both species similarly in previous editions of the Field Guide and also in editions of his Western Birds. The Dickcissel and the Lark Bunting may not be closely related, but the former is in itself treated as aberrant (Check-list..., American Ornithologists' Union (1998)) and the other does not seem to have very close affinities to other sparrow genera. In placing them together this way Peterson, however not by intent, allows for an association of the two species that, from my perspective, inadvertently gives the plate new, implicit meaning.
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Posted by James E. Ducey on June 19, 2015
Labels: historic birds, Townsend's bunting
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