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."