Proposal (580) to South American Classification Committee

Recognize newly described Thripophaga amacurensis

Background: Hilty et al. (2013) discovered and described a new species of Thripophaga, T. amacurensis, from four sites clustered in the southern portion of the Río Orinoco in Venezuela, based on 5 specimens deposited in the Colección Ornitológica Phelps, Caracas (COP), and on audio recordings of at least 15–22 different individuals. As far as is known, the species is restricted to a mosaic of seasonally flooded forest of different heights with small marshes, anthropogenic clearings and seasonally flooded savannas in the Delta Amacuro region. Its range (estimated at 32–48 km²) is further confined by what appear to be totally unsuitable habitats in surrounding regions.

In plumage and morphology, the species is most similar to but diagnosably different from the poorly known T. cherriei, another riverine species that is known from only two sites in the middle Orinoco, some 1000 km upstream from the type locality of amacurensis. The new species differs significantly from the smaller T. cherriei in a suite of mensural characters, and differs further (and diagnostically) in plumage pattern, being much more heavily and extensively buff-streaked dorsally (where cherriei is essentially unstreaked on the hindcrown, nape and mantle) and ventrally, with the abdominal streaks terminating in teardrop-shaped spots that are quite different from the finer, narrow streaking of cherriei, and in color of the throat patch. The two species also appear to differ in vocal characters (songs, duets and call notes), the significance of which was reinforced by multiple reciprocal playback trials conducted by one of the authors, in which pairs of cherriei did not respond to playback of amacurensis and vice versa.

The new species was also shown to differ even more demonstrably in mensural characters, plumage and voice from the disjunctly distributed T. macroura, which is an endemic of coastal and near coastal Atlantic Forest in eastern Brazil. The authors also examined specimens and audio recordings of most of the remaining taxa currently lumped within Thripophaga (while noting that the genus itself is almost certainly not monophyletic), but none of these were as close vocally or morphologically to the new species as the latter was to cherriei and macroura.

Analysis/Recommendation: Based on plumage pattern, vocal characters, habitat preference and distribution, the new species appears to be most closely related to T. cherriei. Having seen and tape recorded a couple of pairs of amacurensis, and having prior extensive field experience with T. macroura, T. fusciceps dimorpha, T. fusciceps obidensis and limited field experience with T. berlepschi, I concur with the authors’ conclusions that T. amacurensis is well-differentiated in plumage, morphology and voice from all of the latter taxa. I also agree with their assessment that the new species most closely resembles (both vocally and morphologically) cherriei, and that the differences between the two forms meet and even exceed all reasonable thresholds for recognition of the two taxa as separate biological species. The reciprocal playback trial results provide yet another data set supporting such recognition.

I therefore strongly recommend a YES vote on this proposal.

Literature Cited

HILTY, S. L,, D. ASCANIO, AND A. WHITTAKER. 2013. A new species of softtail (Furnariidae: Thripophaga) from the delta of the Orinoco River in Venezuela. Condor 115(1):143–154.

Note: The authors suggested “Delta Amacuro Softtail” as the English name, which I think is a good choice, as it emphasizes the only region from which the species is known.

Kevin J. Zimmer

June 2013

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Comments from Robbins: “YES. Hilty et al. did a thorough job in documenting why this should be recognized as a species.”

Comments from Stiles: “YES. Hilty et al.'s evidence, with the nice playback results as the topper, is convincing that amacurensis is a good biological species. The English name is OK, although I wonder if it could be shortened to "Amacuro Soft-tail" without hurting anyone's feelings in Venezuela?”

Comments from Remsen: “YES. Solid evidence for species rank. I agree with Gary that the English name deserves a second look, including the problem that, to be nit-picky, it should be “Amacuro Delta Soft-tail” if we keep the Delta part for an English name.”

Comments from David Donsker: “I thought it would be important to weigh in on the English name of this newly described species. Although it may sound a bit odd to English speakers, Delta Amacuro Softtail rather than Amacuro Softtail or Amacuro Delta Softtail would seem to be the appropriate name. The species, whose habitat and range is in the braided delta of the Orinoco River, is named after the Venezuelan state of Delta Amacuro, which encompasses the Orinoco River delta, not the Rio Amacuro itself.  I don’t suspect that it has even been discovered along the small Rio Amacuro which, at least according to Google maps, doesn’t even seem to have a proper delta of its own.”

Response from Remsen: “David Donsker’s rationale above removes any doubts on the appropriate English name for this species.”

Comments from Pacheco: “YES. Sem qualquer objeção.”

Comments from Nores: “YES. Hilty et al. provided good evidence for why it should be recognized as a species.”