Proposal (82) to South American Classification Committee

 

Treat Oryzoborus funereus as conspecific with O. angolensis

 

Effect on South American CL: This proposal would lump two species currently recognized as separate species on our baseline list; they are treated as conspecific in a majority of current classifications.

 

Background: The two taxa involved consist of the black-bellied, Middle American and mostly trans-Andean funereus group, and the chestnut-bellied, mostly cis-Andean angolensis group. Although the difference in the single plumage character is striking, they seem to otherwise be "identical." They were long treated as separate species (e.g., Hellmayr 1938) until Meyer de Schauensee (1966, 1970) and Paynter (1970) lumped them, based on the existence of intermediate specimens from their contact zone in northern Colombia in Santa Marta region and the Magdalena Valley, as well as the existence of specimens throughout the range of funereus with traces of angolensis-like chestnut in their plumage. The latter has been interpreted as evidence of gene flow or of natural "ancestral" variability in funereus reflecting their common ancestry. Olson (1981), however, said that such specimens were almost always subadult males and, therefore, that the presence of these chestnut feathers did not reflect gene flow.

 

Olson (1981), however, did advocate continued treatment of them as a single species because of the intermediate plumage of specimens in the contact zone.

 

This was followed by Hilty & Brown (1986), Ridgely & Tudor (1989), and Sibley & Monroe (1990) and most other authors.

 

The AOU (1983, 1998), however, continued to maintain funereus as a species, and as a member of that committee, I can report that the rationale was as follows: (1) the two forms maintain themselves as discrete phenotypic units over a huge range that stretches from Mexico to Argentina with no hint of extensive gene flow despite apparently ample opportunity for this in northern Colombia; and (2) Olson's conclusions were based on only 12 specimens from the area of contact that showed intermediate plumage states, and it is not really clear from Olson's paper whether "pure" phenotypic types were also found in this same region (Magdalena Valley). Thus, the AOU preferred to wait for better data, either a more explicit analysis of all specimens from northern Colombia or, preferably, some field data.

 

Analysis: There is not much to analyze here. On the one hand, these two forms are similar, and available data, scanty as it is, suggests extensive hybridization at contact zone. Although explicit comparisons seem to be missing, I cannot find any hint that their songs differ. On the other hand, the abrupt shift in phenotype across a very small area compared to the massive areas occupied by "pure" populations suggests that more thorough analysis is needed to investigate the true nature of the contact.

 

Recommendation: I will vote "NO" on this proposal because in the absence of real data, I see little reason to change our current classification. Perhaps by maintaining a "minority" view in our classification, we will provoke a badly needed study?

 

Literature Cited:

HELLMAYR, C. E. 1938. Catalogue of birds of the Americas. Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13, pt. 11.

HILTY, S. L., AND W. L. BROWN. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey.

MEYER DE SCHAUENSEE, R. 1966. The species of birds of South America and their distribution. Livingston Publishing Co., Narberth, Pennsylvania.

MEYER DE SCHAUENSEE, R. 1970. A guide to the birds of South America. Livingston Publishing Co., Wynnewood, Pennsylvania.

OLSON, S. L. 1981. Interaction between the two subspecies groups of the seed-finch Sporophila angolensis in the Magdalena Valley, Colombia. Auk 98: 379-381.

PAYNTER, R. A., JR. 1970. Subfamily Emberizinae. Pp. 3-214 in "Check-list of birds of the World, Vol. 8" (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, December 2003

 

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Comments from Robbins: "[NO]. I vote "no" if for no other reason than to follow A.O.U. and our current treatment."

 

Comments from Stiles: "[NO]. I agree with Van on this one.  They are likely one species, but more solid published data should be forthcoming before taking issue with 'Papa'."

 

Comments from Zimmer: "NO, although I don't feel on particularly strong ground with this one."

 

Comments from Stotz: "NO. I think the supporting data for this split or lump is weak. Somebody needs to study this in detail."

 

Comments from Jaramillo: "NO _ happy to retain them as different until someone proves otherwise with a more detailed analysis."

 

Comments from Nores: "Yo voto NO a juntar Oryzoborus funereus con O. angolensis. No porque esté convencido de que sean especies separadas, sino porque tampoco hay evidencias contundentes de que sean subespecies."