Proposal (782) to South American Classification Committee
Treat Nothura maculosa and Nothura chacoensis as conspecific
Effect on South American CL: This would lump two taxa that are currently treated as separate species into a single species.
Background: Nothura chacoensis was first described as a subspecies of Nothura maculosa by Conover (1937). After examining more specimens and increasing his sample size, Conover (1950) elevated N. chacoensis to species rank. Subsequent authorities, most of whom never examined the specimens, have been split on whether to regard N. chacoensis as a distinct species or a subspecies of N. maculosa. The apparent sympatry of N. chacoensis and N. m. paludivaga has been argued as evidence that N. chacoensis is a distinct species (Blake 1977, Sibley & Monroe 1990, Cabot 1992). However, a few authorities who examined the specimens felt that the plumage differences between the two taxa were minor compared to the differences between other species of Nothura, and considered them conspecific (Short 1975, 1976, Hayes 1995, Porzecanski 2003). Furthermore, in an unpublished PhD dissertation, Porzecanski (2003) reported that the cytochrome b sequences of two N. chacoensis specimens lack unique substitutions and are identical to those of N. m. paludivaga and nominate N. m. maculosa from Paraguay.
New Information and Analysis: Hayes et al. (2018) examined 15 specimens of N. m. paludivaga and 28 of N. chacoensis from the Paraguayan Chaco in the FMNH and UMMZ. There is no locality where specimens of both taxa were collected; thus, there is no evidence for sympatry. Morphologically the two taxa did not differ in any size or shape variable. Plumage characters overlapped in a few specimens. Hayes et al. (2018) also recorded vocalizations from at least four individuals of N. chacoensis within its known range in the Paraguayan Chaco, and compared them with recordings of N. maculosa posted on XenoCanto. The typical territorial song of N. chacoensis was a very rapid, relatively monotone trill that was virtually identical with the most frequent territorial song of N. maculosa in length, number of notes, rate of notes, and emphasized frequency, and differed substantially from the songs of other species of Nothura (the crucial data in Table 2 and Figure 4 of Hayes et al. 2018 are posted below for convenience).
Recommendation: Based on distributional, morphological, biochemical, and especially vocalization data, N. chacoensis should be regarded as a subspecies of N. maculosa, which has priority.
Blake, E. (1977) A Manual of Neotropical Birds. Vol. 1. University of Chicago Press, Chicago, 724 pp.
Cabot, J. (1992) Family Tinamidae (tinamous). In: del Hoyo, J., Elliott, A. & Sargatal, J. (Eds.), Handbook of the Birds of the World. Vol. 1. Ostrich to Ducks. Lynx Edicions, Barcelona, pp. 112–138.
Conover, H.B. (1937) A new race of the Spotted Tinamou, Nothura maculosa, from the Paraguayan Chaco. Proceedings of the Biological Society of Washington, 50, 227–230.
Conover, [H.]B. (1950) A study of the spotted tinamous, genus Nothura. Fieldiana (Zoology), 31, 339–362.
Hayes, F.E. (1995) Status, distribution and biogeography of the birds of Paraguay. American Birding Association Monographs in Field Ornithology, 1, 1–231.
Hayes, F.E., Rodríguez, O., Thalman, E.R., Castellanos, E.A., & Sterling, J. (2018) Taxonomic status of Paraguay’s only endemic bird, the Chaco Nothura Nothura chacoensis (Aves: Tinamidae). Zootaxa 4392:347–360.
Porzecanski, A.L. (2003) Historical Biogeography of the South American Aridlands: a Molecular Phylogenetic Study of Endemic Avian Taxa. Unpublished Ph.D. dissertation, Columbia University, New York, 314 pp.
Short, L.L. (1975) A zoogeographic analysis of the South American Chaco avifauna. Bulletin of the American Museum of Natural History, 154, 167–352.
Short, L.L. (1976) Notes on a collection of birds from the Paraguayan Chaco. American Museum Novitates, 2597, 1–16.
Sibley, C.G. & Monroe, B.L. Jr. (1990) Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven, Connecticut, 1111 pp.
Floyd E. Hayes, March 2018
Comments from Stiles: “YES: the evidence seems very clear that N. chacoensis is a subspecies of N. maculosa.”
Comments from Robbins: “YES, based on multiple data sets chacoensis should be considered conspecific with maculosa.”
Comments from Pacheco: “YES. There is no evidence to treat Nothura chacoensis as a distinct species of N. maculosa.”
Comments from Remsen: “YES. Great to see that Floyd and his colleagues have taken this one on. This “species” has seemed suspicious just on biogeographic grounds from my days back in the 1970s of perusing Meyer de Schauensee --- it just didn’t seem to make sense.”
Comments from Areta: “YES. N. chacoensis has been one of this clearly invalid species awaiting for a formal paper to show so. It is good to see this happening.”