Proposal (738) to South American Classification Committee
Elevate Crypturellus noctivagus zabele to species rank
Background: From SACC notes: “Tomotani and Silveira (2016) provided evidence that the subspecies zabele might merit treatment as a separate species from Crypturellus noctivagus.”
Pezus zabele Spix, 1825 (= Crypturellus noctivagus zabele) was described as a separate species, but was later considered a synonym of noctivagus (Hellmayr 1906, Peters 1931). With more available material, Hellmayr & Conover (1942) recognized two subspecies, reviving the name zabele for the inland northeastern Brazilian birds and distinguishing them from nominate C. noctivagus (from the east and south Brazil) by an overall paler color, a well-defined superciliary stripe, and broader bars in the wing-coverts and remiges. They also noticed possible sexual dimorphism in C. n. zabele. Subsequently, all works (e.g. Blake 1977, Davies 2002) followed the taxonomy proposed by Hellmayr & Conover (1942).
Regarding distributions, the two taxa do not overlap. Crypturellus n. zabele is endemic to the Caatinga, also marginally inhabiting the Cerrado, and occurs in northeastern Brazil from Piauí to northwest Minas Gerais states, whereas C. n. noctivagus is endemic to the Atlantic Forest, occurring from Bahia to Rio Grande do Sul states.
Consistent differences in plumage color and pattern, morphometric characters, color of tarsus, egg color and egg shape were found by Tomotani and Silveira (2016) after analyzing 67 skins of adult Crypturellus noctivagus, including the holotypes of both taxa (i.e., the nominal noctivagus and zabele), and 12 eggs.
The voice of C. n. zabele also seemed to have a slightly lower frequency than that found in C. n. noctivagus, but there was a great overlap between the two taxa (sample size: n = 10 for C. n. noctivagus, n = 5 for C. n. zabele; Tomotani and Silveira, 2016).
The overall plumage of C. n. zabele is paler than that of C. n. noctivagus and they also differ in morphometric characters and egg shape and color. However, the most striking differences appear when we compare the tarsus coloration and the females’ breast plumage. These diagnostic characters are critical to the recognition of these taxa as two distinct, independent lineages, which must be considered as separated species under the Phylogenetic Species Concept (Tomotani and Silveira, 2016).
It seems to me that under the BSC the treatment must remain unchanged.
Blake, E. R. 1977. Manual of Neotropical birds, v. 1. Chicago: University of Chicago Press.
Davies, S. 2002. Ratites and tinamous (Bird families of the world). Oxford: Oxford University Press.
Hellmayr, C. E. 1906. Revision der Spix´schen Typen brasilianischer Vögel. Abhandlungen der Mathematisch-Physikalischen Klasse der Königlich Bayerischen Akademie der Wissenschaften, 22: 561-726.
Hellmayr, C. E. and B. Conover. 1942. Catalogue of the birds of the Americas and adjacent islands. Field Museum of Natural History, Zoological Series, 13, pt. 1, 1-636.
Peters, J. L. 1931. Check-list of birds of the world, vol. 1. Harvard University Press, Cambridge, Massachusetts.
Tomotani, B. M. and L. F. Silveira. 2016. A reassessment of the taxonomy of Crypturellus noctivagus (Wied, 1820). Revista Brasileira de Ornitologia, 24: 34-45.
Fernando Pacheco, January 2017
Comments from Remsen: “NO. Absence of discrete vocal differences suggests subspecies rank under BSC framework in Tinamidae. The number and quality of other differences, however, suggests that this is one of those inevitable borderline cases.”
Comments from Stiles: “NO. The existence of the morphological variation cited in itself is sufficient for recognition of zabele as a good subspecies and perhaps as a phylogenetic species, but especially in tinamous, divergence in vocalizations should also be evident, but Fernando notes much overlap here, such that I agree with his assessment that under the BSC, its status should not change.”
Comments from Areta: “NO. The minor color differences in tarsi (olivaceus yellow in noctivagus, pure yellow in zabele), plumage (paler in the dimorphic zabele) and eggs (greenish in noctivagus, bluish in zabele) and lack of diagnostic vocal differences in these tinamous support their treatment at the subspecific level.”
Comments from Zimmer: “NO. As stated by Fernando, the vocalizations are not diagnosably different, which, I would think, for evaluating species-limits in tinamous, would be a deal-breaker. The stated plumage, bare-parts and eggshell color differences are certainly worthy of being recognized at the subspecific level, but no more, in my opinion. As regards Alvaro’s concerns about the differences in habitat preferences between the two taxa: they may not be as different as it sounds. I have always found zabele to be in the taller, more humid micro-climates within the caatinga, particularly in what might most properly be called mata-de-cípo, or vine forest, with lusher vegetation and, often, with significant patches of terrestrial bromeliads. I don’t seem to find them in the really arid, scrubby caatinga. At least in the southern part of its range, noctivagus seems to be most common in some of the taller coastal restinga woodland formations, growing on sandy soils, with dense understory growth, and abundant terrestrial bromeliads. Even up in Espírito Santo, near the northern limit of its range, the forest habitats where I tend to find them most often, have a different, more stunted feel to them, with a densely vegetated understory and seemingly growing on poorer soils. So, there are some distinctions, yes, but they are perhaps subtler than implied by caatinga/cerrado versus mata Atlantica.”
Comments from Jaramillo: “NO ... although, I am most troubled though by the difference in habitat of the two forms. A major habitat shift like this seems unusual in a subspecies, but then again, there just may not have been enough time since the shift, for biological species level differences to evolve.”
Comments from Claramunt: "NO. The photographs show striking differences between specimens of noctivagus and zabele but the analysis of character variations suggest more overlap and intermediate phenotypes (Table 2). The most distinctive characters are tarsus color but were assessed in an unknown subsample of the skins examined, and lack of solid gray breast in females, but sample size is low (three female zabele skins). In addition to a larger sample of the most diagnostic traits, what is missing is an analysis of the geographic variation of characters and an analysis of potential intermediate individuals. That analysis could demonstrate whether noctivagus and zabele maintain phenotypic integrity in multiple traits despite parapatry (suggesting reproductive isolation) or, alternatively, represent an intraspecific cline associated with a strong environmental gradient."
Comments from Robbins: "NO. The lack of vocal differentiation is my main concern. Also, points made by Claramunt need to be addressed before elevating this to species rank."
Comments from Cadena: “NO. I agree that differences might be sufficient to recognize diagnosable taxa (i.e. phylogenetic species), but I see no compelling evidence to recognize these taxa as distinct reproductively isolated populations.