Proposal (758) to
Elevate Thamnistes anabatinus rufescens to species rank
Effect on SACC: This proposal would add a species to the list by removing the subspecies rufescens from Thamnistes anabatinus and elevating it to species rank.
Background and Analysis: The Russet Antshrike, T. anabatinus, is primarily a resident of foothills forests of the northern Andes (both slopes in Colombia and Ecuador) and Middle America. Six subspecies are currently recognized (Peters 1951). Historically its vocalizations were largely overlooked and poorly recorded as it is a participant in noisy mixed-species flocks of the lower canopy to the upper understory. Recent recordings expanded the vocal inventory and provided a basis for analysis of populations and consideration of taxonomic rank (Isler and Whitney 2017). As a result, multiple (five or more) vocal characters of two types of song of rufescens, the southernmost population, were found to differ diagnosably from all other populations. Currently scarce in recordings, the calls of rufescens are also likely to be found to differ diagnostically when a sufficient number of samples is acquired. The plumage of rufescens is also distinct (Zimmer and Isler 2003).
Recommendation: Diagnosable differences in vocalizations and plumage meet our yardstick (Isler et al. 1998) for elevation of rufescens to species rank.
English name: We recommend that T. rufescens be designated Rufescent Antshrike, reflecting its scientific name.
Isler, M. L., P. R. Isler, and B. M. Whitney. 1998. Use of vocalizations to establish species limits in antbirds (Passeriformes; Thamnophilidae). Auk 115:577–590.
Isler, M. L., and B. M. Whitney. 2017. Species limits in the genus Thamnistes (Aves: Passeriformes: Thamnophilidae): an evaluation based on vocalizations. Zootaxa 4291 (1): 192–200.
Peters, J. L. 1951. Check-list of birds of the world, vol. 7. Museum of Comparative Zoölogy, Cambridge, Massachusetts. 318 pp.
Zimmer, K. J., and M. L. Isler. 2003. Family Thamnophilidae (typical antbirds). Pages 448–681 in Handbook of the Birds of the World. Volume 8: Broadbills to Tapaculos (J. del Hoyo, A. Elliot, and D. A. Christie, Editors). Lynx Edicions, Barcelona, Spain.
Mort Isler and Bret Whitney, October 2017
Photos of specimens from Remsen: Left side, trans-Andean taxa from top to bottom: nominate anabatinus, saturatus, coronatus, intermedius; right side, cis-Andean aequatorialis, rufescens.
Comments from Whitney (who wrote this comment after suggestion that the name would probably be changed to something new, or some such thing, because no one has formally suggested that T. anabatinus needs a new English name): "Just some quick thoughts on the English names:
"Why on Earth would we change the name of Thamnistes anabatinus to something new? Russet Antshrike is a name of long-standing, and is perfectly fine. I would expect to change it ONLY if we were to hyphenate it, to greatly aid people to understand what antbird complex it pertains to. For example, we might have Northern Russet-Antshrike and Southern (or Rufescent) Russet-Antshrike. This would be right in-line with what has been adopted recently for other such thamnophilid species groups, such as warbling-antbirds and scale-backed antbirds; their hyphenated group names were readily adopted by the birding community (i.e., folks who typically do not use scientific names), and are functioning effortlessly. Frankly, I much prefer these more informative, hyphenated English names, especially for groups that have more than two taxa currently considered species. Because the Russet Antshrike group is now only two, just as is the Undulated Antshrike group, I’m more “at-ease” with lacking a group English name.
Alternatively, we could introduce an even more radical change to the system, such as what’s being considered for Epinecrophylla — call them all something completely new: “stipplethroats”. The good in this is retention, even strengthening, of a group’s English name (as if it were a genus)
Comments from Areta: "YES. Vocal differences between rufescens and the reminder of subspecies in slow songs are diagnostic. So far, the recorded calls are also diagnostic between these two groups. The lack of recordings of rapid songs in trans-Andean populations is curious, but since aequatorialis possess a slow song presumably identical to those of trans-Andean birds it might be the case that they also share the same rapid song type. However, as stated by Mort and Bret, the status of aequatorialis will need to be assessed in the future once more vocal data is available."
Comments from Stiles: "YES to splitting rufescens from the rest of T. anabatinus; vocal, genetic and plumage data seem quite sufficient for this. However, I agree with Bret with regard to the “necessity” of giving both taxa hyphenated group names; “Rufescent Antshrike” (or something similar) while leaving all the rest as “Russet Antshrike” seems like a simpler and more sensible solution.
"This leads me to a comment on what I am coming to see as a rather excessive rigidity regarding the SACC stance on English (as opposed to scientific (Latin) names. Scientific nomenclature is governed by a strict set of rules (the ICZN code). Latin is no longer a “living” language (though due to ecclesiastical use, it was through the Middle Ages). However, such strictness is not as applicable to names in currently living languages, which evolve according to prevailing usage. Hence, if a new vernacular name is given to a species or group that is more descriptive or diagnostic and also acquires wide usage, I see no reason not to accept it. I am thus less than impressed by freezing a name according to its past “track record”, especially when the older name was given by authors with no field experience with the bird or group in question. This is in contrast to the perhaps overly-maligned “field-guide taxonomy”: the main users of English names may be better served by adopting the newer name, especially when suggested by authors with extensive field experience with the birds (and often the authors of field guides!). Although splitting of species is a taxonomic decision for which strict nomenclatural rules apply for assigning Latin names, the same need not be the case for applying English names – as living languages evolve, there may well be no perfect, permanent name in the long run, but newer and definitely more evocative names might have longer lifetimes and are more likely to approach stability, in at least the foreseeable future. I might note that the ICZN is somewhat flexible here as well, setting aside priority when a subsequent name has acquired sufficiently universal use for a sufficient time. An interesting point here is that unlike English, Spanish does have a governing body for assuring linguistic purity (The Real Academia), but even it recognizes that usage patterns change, to the point that it now publishes its authoritative dictionary on-line to accommodate such changes and additions to the Spanish language."
Comments from Zimmer: “YES. Songs (and probably calls) of rufescens have been demonstrated to differ diagnosably from those of the other subspecies in the anabatinus-complex, and these differences are concomitant with diagnosable differences in plumage, thereby meeting the Isler et al (1998) yardstick for elevating thamnophilid taxa to species-rank. Given that there are only 2 species involved, I agree with others that it is better to retain the established English name of “Russet Antshrike” for the anabatinus-group, and to go with the streamlined “Rufescent Antshrike” for rufescens, as opposed to using a clunkier, hyphenated group-name.”
Comments from Remsen: "YES. Just handling specimens of these two makes me wonder why they were ever considered conspecific. Now, we have convincing vocal data that indicate that these two have diverged to the point that unrestricted gene flow would be unlikely. See photographs above for how distinctive is the plumage of rufescens: vaguely striped dorsally, and more rufescent ventrally. Also note that aequatorialis does group better with trans-Andean taxa than cis-Andean rufescens
“Regarding English names, clearly a separate proposal would be needed. The opposing view to Gary’s points is that stability should figure into any decision because any novel names make it difficult to negotiate older literature, just the way we have an unfortunately difficult time reading older English texts. Further, finding “better” names is a subjective exercise that is theoretically interminable.” Also, I think it’s a bad idea in this case for one of the daughters to retain the parental name. I may have a solution. The English name for nominate anabatinus used by Ridgway was Tawny Antshrike, and Russet was used for saturatus only; so, when Eisenmann (?) selected an E name for the species, he picked Russet. I think Tawny applies equally well. If we go with Tawny for anabatinus (the E name actually applied to that taxon) and Rufescent for rufescens, we can avoid the problems of compound names and the parent-daughter confusion problem.
Comments from Pacheco: “YES. The combination of consistent differences in vocal repertoire and in plumage is convincing to justify species rank treatment.”
Comments from Stotz: “YES. I am okay, but barely, with Rufescent and Russet antshrikes.”
Comments from Jaramillo: “YES, and I would avoid the hyphenated name and go for Rufescent and Russet Antshrikes.”
Comments from Robbins: “YES, the vocal data along with the plumage differences strongly support recognizing rufescens as a species.”