Proposal (731x) to South American Classification Committee

Elevate Ortalis motmot ruficeps to species rank (2)

Due to the publication of our article, we would like to reopen proposal number 731.

In the newly published article below, we performed a vocal, morphological, and plumage comparison between the northern O. m. motmot and the southern O. m. ruficeps. These taxa present differences in tail coloration but are otherwise undiagnosable in terms of plumage. Ortalis m. ruficeps is, however, markedly smaller and lighter than O. m. motmot, with no overlap in size or weight. We also found vocal differences between O. m. motmot and O. m. ruficeps, no overlap in geographic distributions, and no signs of hybridization across its range. Based on the available data, Ortalis m. ruficeps thus must be considered a valid and endemic species to Brazil.

Tomotani, B. M., Silveira, L. F. & Pacheco, J. F. (2020) Morphology and vocalization support specific status of the Chestnut-headed Chachalaca, Ortalis motmot ruficeps (Wagler, 1830) (Aves; Galliformes; Cracidae). Pap. Avulsos Zool., 2020; v.60: e20206012. http://doi.org/10.11606/1807-0205/2020.60.12

Luis Fabio Silveira & Fernando Pacheco, May 2020

Comments from Claramunt: “YES. A subtle but diagnostic difference in plumage plus a dramatic body size difference and some vocal distinction suggest these two birds are (minimally) different species.”

Comments from Bonaccorso: “YES. Plumage differences are indeed minimal, and I think that the number of data points for vocal characters for O. ruficeps is too few to draw any conclusion in that regard. However, differences in size are consistent and geographic distributions fit the idea of two independent evolutionary units.”

Comments from Jaramillo: “YES, based on the previous comments I made, and the new data...well now there is something to hang a hat on.”

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Proposal (731) to South American Classification Committee

Elevate Ortalis motmot ruficeps to species rank

Background: From SACC notes: “Sick (1993, 1997) treated ruficeps of eastern Brazil as a separate species from Ortalis motmot.”

“Ortalis ruficeps Wagler, 1830” was treated as an enigmatic Brazilian taxon of uncertain origin until Todd (1932), using a series of specimens obtained in the lower Amazon, treated it as a subspecies of Ortalis motmot, a treatment immediately supported by Peters (1934). Subsequent reference works maintained this treatment without comment (Hellmayr and Conover 1942; Vaurie, 1968; Blake 1977; Pinto 1978) until Sick (1985) treated ruficeps a separate species: Ortalis ruficeps. Sick proposed that all Brazilian species of Ortalis (except O. canicollis) would be better treated as allospecies of O. motmot superspecies. We do not know why Sick omitted O. subaffinis. Sick´s classification (repeated in Sick 1993, 1997) was the exact opposite of the treatment proposed by Delacour & Amadon (1973), who treated O. guttata, O. subaffinis, O. superciliaris, O. araucuan, O. squamata, O. motmot and O. ruficeps (but also O. columbiana) as mere subspecies of an expanded O. motmot, appropriately called Variable Chachalaca.

Separated by the Amazon River at its widest stretch, Ortalis motmot ruficeps is decidedly smaller in all measurements and in both sexes than O. m. motmot, with virtually no overlap (Blake, 1977). Blake (1977) also mentioned subtle differences in color; however, examination of a large series of both taxa at MZUSP showed that the color differences (specially in head color) are related to individual variation and/or age, with no taxonomic significance.

A preliminary examination of the vocal repertoire of these taxa revealed differences in phraseology and velocity of notes, being slower in O. m. ruficeps.

Two examples of the O. m. motmot song are available here:

http://www.xeno-canto.org/272216 (Suriname)

http://www.xeno-canto.org/226988 (Venezuela)

Two examples of the O. m. ruficeps song are available here:

http://www.xeno-canto.org/312921 (Santarém, Pará)

http://www.wikiaves.com/757077 (Belterra, Pará)

Analysis and Recommendation: In contrast to Delacour and Amadon (1973), other allotaxa in this complex are already treated at the species rank by SACC, e.g., O. columbiana (see Proposal 439), Ortalis araucuan (see Proposal 478), and O. squamata (see Proposal 478); and O. superciliaris is traditionally treated as a separate species. In view of the consistent differences of size between O. m. motmot and O. m. ruficeps and their apparent vocal differences, we commend treatment of O. ruficeps as a separate species; thus, we recommend a YES on this proposal.

Literature Cited:

BLAKE, E. 1977.  A manual of Neotropical Birds, Vol. 1. University of Chicago Press, Chicago.

DELACOUR, J. T., AND D. AMADON. 1973. Curassows and related birds. American Museum of Natural History, New York.

HELLMAYR, C. E., AND B. CONOVER. 1942. Catalogue of birds of the Americas. Field Museum Nat. History Publ., Zool. Ser., vol. 13., pt. 1, no. 1.

PETERS, J. L. 1934. Check-list of birds of the world, vol. 2. Harvard University Press, Cambridge, Massachusetts.

PINTO, O. M. O. 1978. Novo catálogo das aves do Brasil, parte 1. São Paulo.

SICK, H. 1985. Ornitologia Brasileira, uma introdução. Editora University Brasília, Brasília.

SICK, H. 1993. Birds in Brazil. Princeton University Press, Princeton, New Jersey.

SICK, H. 1997. Ornitologia Brasileira. Editora Nova Fronteira, Rio de Janeiro.

TODD, W.E.C. 1932 Critical Notes on the Cracidae. Proceedings of the Biological Society of Washington 45: 209-214.

VAURIE, C. 1968. Taxonomy of the Cracidae (Aves).  Bulletin American Museum Natural History 138: 131-260.

Fernando Pacheco & Luis Fabio Silveira, November 2016

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Comments from Areta: “NO. Data are suggestive of two species-level taxa in this complex, but detailed morphometric and vocal analyses should be properly published before an informed decision can be made.”

Comments from Stiles: “NO for the present. The good series of both forms should suffice for a thorough morphological analysis (not reported here), and the data on vocalizations should at least be presented and salient differences between them pointed out (with n=2), statistical analyses would be unwarranted, but any discrete, qualitative differences should be evident.”

Comments from Stotz: “NO. My guess is that we will eventually split these. As the proposal notes, other allotaxa in this complex have been split off as separate species. But I agree with the others that we need some published evidence and a clear statement of what the differences in the voices are and how different they are compared to other members of the complex.”

Comments from Jaramillo: “NO: Even a quick publication would be necessary to have something to hang a hat on.”

Comments from Zimmer: “YES. As others have stated, I suspect that ruficeps will eventually prove to be a distinct species. But I think the otherwise unpublished data presented here are not enough to make the case. I can hear apparent qualitative differences in the small vocal samples linked in the Proposal, but the syntax of the samples sounds fairly similar. As I have cautioned before when talking about vocal analyses of Chachalacas, Trumpeters and Parrots, differences in the numbers of birds vocalizing, and in the social context of the vocalizations can introduce variation into the samples that might tend to exaggerate apparent differences that are not really there. This does appear to be yet another case of a Peters-style lump that was based on little or no justification, and, as such, I don’t think we need to hold this to an incredibly high standard of evidence. However, with morphological distinctions between the two taxa confined to mensural differences (and these apparently not 100% diagnostic), and the vocal evidence confined to n = 2, I’d prefer to wait for a bit more analysis.”

Comments from Robbins: "NO. More thorough analyses are needed before recognizing Ortalis motmot ruficeps as a species."

Comments from Claramunt: “NO. A detailed analysis of the phenotypic variation is needed. There is important phenotypic variation from North to South, but we don’t know if it is part of a cline within a single lineage or sign of species divergence.”

Comments froim Remsen: "NO. A more through analysis is required, with boosts in N in specimens and localities. That two allopatric taxa do not overlap in measurements is of little value in governing species limits within a genus. Vocalizations are suggestive but require a published, formal analysis with larger N."