Proposal (679) to South American Classification Committee
Recognize Nystalus obamai Whitney et al. 2013 as a species
Background: Nystalus puffbirds are widespread in Amazonia, especially south of the Amazon, occurring from the base of the Andes east to eastern Pará and Tocantins in eastern Brazil. Traditionally two taxa have been recognized, striolatus Pelzeln 1856, of western Amazonia (east to Mato Grosso) and torridus Bond and Meyer de Schauensee 1940, of eastern Brazil.
The song of Amazonian Nystalus basically is a simple two-parted whistle, but Whitney et al. (2013) reported that there were three geographically distinct vocal types. The song of birds of western Amazonia has a brief introductory stutter to the first phrase. This feature is lacking in songs of birds elsewhere; there is a very slight stutter in some, but not all, birds of the Madeira-Tapajós interfluvium (their Figure 4E); but even where present, this stutter is much less developed than in birds of western Amazonia. And in birds of eastern Amazonia, the song has "a continuous, falling then rising" initial phrase, with no stutter.
There is very little morphological variation across Amazonia. The western group is characterized by numerous wholly blackish feathers on the mantle, these feathers lacking pale terminal fringes. Birds of the Madeira-Tapajós population are darker overall, the mantle is browner (less blackish), and the feathers of the mantle usually if not always have pale terminal fringes. The plumage of the eastern population is less well-known; of the two specimens studied in detail by Whitney et al., one resembled birds of the western population, whereas the second was more similar to birds of the Madeira-Tapajós interfluvium.
Finally, genetic differentiation among these three groups is modest, as assessed by 1025 base pairs of DNA of the mitochondrial cytochrome b gene: with small sizes (n = only 1-2 per population), these groups are separated from each other by uncorrected genetic distances of 3-3.5%.
The name striolatus applies to the eastern population. Whitney et al. (2013) documented that the name torridus must refer to birds of the Madeira-Tapajós interfluvium, leaving birds of western Amazonia without a name. Therefore they described the western population as Nystalus obamai.
SACC previously considered the status of Nystalus obamai in Proposal 617, which also proposed recognizing torridus as a species (i.e., a proposal to recognize three species of Nystalus in Amazonia). This proposal did not pass.
New information: There isn't any. Although Proposal 617 did not pass, several committee members offered comments suggesting that they would consider recognizing obamai as a species, were this option presented as a standalone proposal (with torridus thus remaining as a subspecies of striolatus). Please review Proposal 617, with particular reference to the comments on the proposal by those casting votes, as well as the extensive comments submitted by Whitney. In sum:
• The only genetic evidence to date on these puffbirds comes from a single gene, and with very small sample sizes (1 of striolatus and torridus, 2 of obamai); and genetic divergences are modest (3-3.5% in pairwise comparisons).
• Morphological differences between striolatus, torridus, and obamai are slight.
• The three taxa differ most notably in voice. See in particular Whitney's comments to Proposal 617, in which he pointed out that the sample size for the vocal analysis in Whitney et al. (2013) was greater than was indicated in the paper itself (see the supporting information), and in which he emphasized "the vocal type is still 100% diagnostic of obamai".
Recommendation: I am agnostic on the question of whether obamai should be recognized as a species; my only interest here is in following through on the suggestion from several members of SACC that there should be a revised proposal to focus solely on the status of obamai. English names will be considered in a separate proposal, if necessary.
Whitney, B.M., V.Q. Piacentini, F. Schunck, A. Aleixo, B.R.S. Souza, L.F. Silveira, and M.A. Rêgo. 2013. A name for Striolated Puffbird west of the Rio Madeira with revision of the Nystalus striolatus (Aves: Bucconidae) complex. Pages 240–244 in J. del Hoyo, A. Elliott, J. Sargatal, and D.A. Christie, editors, Handbook of the birds of the world. Special volume: new species and global index. Lynx Edicions, Barcelona.
Tom Schulenberg, August 2015
Comments from Remsen: “YES. The vocal differences are convincing to me for species rank, although of course some standardized playback trials would greatly improve my confidence.”
Comments from Zimmer: “YES. This proposal singles out obamai from the three-way (and less strongly supported in my opinion) split proposed in Proposal #617. As far as I can determine, there is substantial individual plumage variation within this species complex, even between individuals from the same location, so I consider any purported morphological distinctions between obamai, torridus and striolatus to be taxonomically uninformative at this juncture. Similarly, sample sizes upon which the genetic data were based are small. But the sample sizes supporting the diagnostic vocal differences are more robust, and a split across the Madeira certainly fits a well-established biogeographic pattern. I don’t think the case for splitting torridus is as strong, at least not based on current data.”
Comments from Stiles: “YES. Albeit somewhat hesitantly, given that the vocal differences of obamai from the other forms of striolatus are 100% diagnosable by present evidence (however, the differences are not terribly great, and I agree with Van that playback experiments would be very useful for deciding the case).”
Comments from Areta: “Difficult proposal. I move between a cautious NO, and a hesitant YES, and cannot convince myself for a definitive vote.
“Following Bret's recommendation in Proposal 617, I examined the Supplementary material. Sound for figure 4C is missing from the Supplementary information section, so I could not compare it against other recordings. It looks like in the search for high-contrast figures, the sounds of obamai were somewhat "misrepresented" by spectrograms in Figure 4: I see (and listen to) a single initial note, followed by an undulating note linked (or perhaps just barely separated from) the more continuous whistle. The contrast between what I hear/see when making my own spectrograms and what is illustrated in Figure 4 is more noticeably with the recordings of obamai, especially so with 4B, which looks very different in the spectrogram's paper but which sounds and looks like many other obamai recordings from other localities. I would say that structurally, the song of obamai is very similar to those of other members of the complex, being composed by three notes: a whistle, an undulating whistle continued into a long segment, and the final whistled note. However, a random examination of recordings shows some variation, and indeed a recording containing typical obamai song (MLNS13611 from Madre de Dios, Peru), also includes a song from a presumed mate of the typical obamai singing bird, which is very similar to that of one torridus (4E) used in the paper. Improved time and frequency resolution in the spectrograms should have helped perceive more distinctions or similarities between vocalizations (e.g., compare 4E here and in the paper).
“The morphological diagnosis is not exhaustive or very convincing (all agree in that plumage differences are minor), and this, coupled with the few individuals sampled for the genetic analysis (divergence is around 3% between all three pairs of taxa, with torridus and striolatus being represented by one sample and obamai by two), the fact that birds respond to whistled imitations of their songs and to playback of each other (although no rigorous playback tests have been performed), and the similarities in their vocalizations make me unsure on to whether obamai deserves species status, despite its diagnostic song with the undulating whistle.
obamai-MLNS13611 (typical obamai
Comments from Robbins: “YES. However, after reading the insightful comments by Areta, one of the two “diagnostic” features, primary song, of obamai comes into question. Thus, we are left with the genetic data, which is based on one gene with very small sample sizes. Nonetheless, even with these caveats I will, for now, support recognition of obamai as a species.”
obamai-MLNS13611 (torridus-like) torridus-4E (first two notes)
Comments from Pacheco: “YES, based on vocal differences and genetic divergence.”
Comments from Jaramillo: “YES – Similarly to others, I am hesitant because the 100% diagnostic differences are slight. Having playback experiments would be great, although I realize this is not always easily obtained. But we do know that voice is hardwired in this group, so a diagnostic difference in this key trait is enough for me to ok the notion that obamai deserves a name.”