Proposal (67) to South American Classification Committee
Treat Basileuterus roraimae as separate species from B. bivittatus
Effect on South American CL: This proposal would split our Basileuterus bivittatus into two species, with recognition of northern roraimae as a separate species.
Background: The bird we treat as one species, Basileuterus bivittatus (Two-banded Warbler), has a disjunct distribution, with one subspecies group in the Tepui region of (mostly) Venezuela and the other in the Andes from southern Peru to northern Argentina. This follows the traditional classification (e.g., Hellmayr 1935, Meyer de Schauensee 1966, 1970, Lowery & Monroe 1968, Meyer de Schauensee & Phelps 1978, Ridgely & Tudor 1989, Curson et al. 1994, Sibley & Monroe 1990).
The subspecies roraimae is very similar in plumage to nominate bivittatus, differing primarily in a "cleaner" head pattern, with more sharply defined orange coronal stripe and black lateral stripes. The southernmost subspecies argentinae could be considered the most divergent of the three in that its coronal stripe is bright yellow, not orange. LSUMZ material from depto. Santa Cruz shows that the population there is actually a mix of yellow and orange-crowned birds.
New information: Hilty (2003) treated roraimae as a separate species from bivittatus without explanation.
Analysis: The plumage differences between roraimae and bivittatus are less, in many cases far less, than those between many taxa currently treated as same subspecies in Basileuterus. Without any vocal evidence, this one has no evidence to even vaguely support it other than the "disjunct "distribution. But "how disjunct" do distributions have to be to be used as criteria for defining species limits? [Tangentially .... classifying distributions into "disjunct" and "not disjunct" is one of the worst cases I know of inflicting a typology on a continuum. Most species' ranges consist of many "slightly disjunct" populations -- it all depends on the geographic scale at which they are examined. The presumed conceptual meaning of "disjunct" is something like "so far apart that there is no current gene flow," but that can happen on opposite sides of severe barriers like rivers and mountains over distances of less than a kilometer that would not normally be described as "disjunct."]
Recommendation: I vote "NO" on this proposal. Only a quantitative study of vocalization differences, if they exist, would convince me on this one.
CURSON, J., D. QUINN, AND D. BEADLE. 1994. Warblers of the Americas. Houghton Mifflin.
HELLMAYR, C. E. 1935. Catalogue of birds of the Americas. Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13., pt. 8.
HILTY, S. L. 2003. Birds of Venezuela. Princeton University Press, Princeton, New Jersey.
LOWERY, G. H., JR., AND B. L. MONROE, JR. 1968. Family Parulidae. Pp. 3-93 in "Check-list of birds of the World, Vol. 14" (Paynter R. A., Jr., ed.). Museum of Comparative Zoology, Cambridge, Massachusetts.
RIDGELY, R. S., AND G. TUDOR. 1989. The birds of South America, vol. 1. Univ. Texas Press, Austin.
SIBLEY, C. G., AND B. L. MONROE, JR. 1990. Distribution and taxonomy of birds of the World. Yale University Press, New Haven, Connecticut.
Van Remsen, October 2003
Comments from Robbins: "Given that there isn't any new information I vote "no". As Van points out, we need at least some data to support a split."
Comments from Jaramillo: "NO -- Since there is no new information they need to stay under one species. I bet they are two however."
Comments from Zimmer: "I vote "NO". As with many previous proposals, I think we need some published rationale."
Comments from Stiles: "NO pending publication of solid evidence. As in many other such cases, this will probably prove to be correct but I do not believe in changing things without published evidence."
Comments from Nores: "NO. Mientras no haya datos genéticos o de canto que demuestren que es una especies diferente, prefiero ser conservativo. Las diferencias de color parecen ser subespecíficas."