Proposal (797) to South American Classification Committee

A. Split extralimital Aramides albiventris from Aramides cajaneus

B. Change English name of Aramides cajaneus from Gray-necked Wood-Rail to Gray-cowled Wood-Rail

Below is a proposal accepted and implemented by NACC (Chesser et al. 2016, Auk), posted here with permission of Rafael Marcondes. Although actual the split is extralimital to the SACC area, it affects SACC in that NACC now treats “our” species under a more restricted geographic range (which is not reflected in SACC list) and English name, i.e. Gray-cowled Wood-Rail.

The vote for SACC is in two parts. The rationale for A is outlined in the NACC proposal. The English name did not go through a formal proposal system but was discussed at length through emails. Obviously, NACC went with creating new names for both daughters, and also attempted to maintain a connection (Gray-something) between the English names of the broader and narrower A. cajaneus to make the new name easier to remember. I recommend a YES on both:

A. Recognize the split of n. Middle American taxon as a separate species, Aramides albiventris, from Central American and South American Aramides cajaneus.

B. (for English name voter subgroup): If YES on A, then change the English name of our Gray-necked Wood-Rail to Gray-cowled Wood-Rail.

Van Remsen, June 2018

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Comments from Jaramillo: “A - Yes, I remember hearing my first albiventris after being familiar with cajaneus and wondered….what is that bird? They sound quite different to my ear.

B – Yes. Gray-cowled Wood-Rail works for me.”

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Proposal: Split Rufous-naped Wood-Rail Aramides albiventris from Gray-necked Wood-Rail Aramides cajaneus

Background: The taxa presently associated with Aramides cajaneus had a somewhat convoluted taxonomic history in the 19^th and early 20^th century. Aramides cajaneus itself was described based on a bird from Cayenne, French Guiana, and several names were proposed in the following centuries for Central American birds allied to it. The status (specific or subspecific) and limits of these putative taxa, however, were rather controversial (reviewed in Marcondes and Silveira 2015), until Peters (1934) and Hellmayr and Conover (1942) lumped them all as subspecies of Aramides cajaneus. That treatment has been followed, largely uncritically, into the modern era (e.g., Taylor 1996, Taylor 1998), such that A. cajaneus is considered a polytypic species containing nine subspecies, eight of which occur in the NACC area.

New information: Marcondes and Silveira (2015) reviewed the morphological (very good sampling – 800 skins and good geographical coverage) and vocal (not such good sampling - 92 recordings, with significant geographical gaps, but see below) variation of Aramides cajaneus throughout its range. In what concerns this Committee, we established that the mountains of the Chorotega Volcanic Front in lower Central America segregate populations that differ considerably in morphology and voice. In comparison with birds from South America, Panama and southwestern Costa Rica (Aramides cajaneus sensu stricto), those from northeastern Costa Rica and further north, to which the name Aramides albiventris Lawrence 1868 applies, have a much more strongly-colored nape, have longer bills and tarsi, and a different song.

Plumage differentiation (Marcondes and Silveira 2015, fig. 3), albeit shown in only one plumage patch, is fixed, and the two forms replace each other parapatrically with no intermediates (Marcondes and Silveira 2015, fig. 2). Morphometric differentiation is also sharply geographical, with clear discontinuity in variation in the area where the two forms abut each other (Marcondes and Silveira 2015, fig. 4). Finally, most striking is the difference in song. The vocal sampling for A. albiventris is rather sparse (Marcondes and Silveira 2015, fig. 5), but we argue that this is not an issue because there are no vocal intermediates between the two taxa. In fact, the songs are different to the point that it is impossible to come up with hypotheses of homology between their elements (Marcondes and Silveira 2015, figs. 6 and 7), and the degree of differentiation is comparable to that observed between A. cajaneus and other species in the genus, such as A. ypecaha or A. saracura. Below are links to examples of the song of each taxa:

A. cajaneus: http://macaulaylibrary.org/audio/51765

A. albiventris: http://macaulaylibrary.org/audio/23151

Recommendation:

We suggest that sharp parapatric differentiation from A. cajaneus in plumage, morphometrics, and especially song are enough indirect evidence to corroborate species status for A. albiventris under any species concept. We propose the English name Rufous-naped Wood-rail. White-bellied Wood-rail, as proposed by the IOC (http://www.worldbirdnames.org/updates/proposed-splits/), is not adequate, because this character is not constant within the species (Marcondes and Silveira 2015, fig. 10).

Literature cited:

Hellmayr CE, Conover B (1942) Catalogue of birds of the Americas and the adjacent islands in Field Museum of Natural History, part 1, number 1. Field Museum of Natural History Zoological Series vol. 13, 636 pp.

Marcondes RS, Silveira LF (2015). A taxonomic review of Aramides cajaneus (Aves, Gruiformes, Rallidae) with notes on morphological variation in other species of the genus. Zookeys 500:111-140.

Peters JL (1934) Check-List of Birds of the World, volume 2. Harvard University Press, Cambridge, Massachusetts, 401 pp.

Taylor PB (1996) Family Rallidae. In: Del Hoyo J, Elliot A, Sargatal J (Eds.) Handbook of the Birds of the World, vol. 3. Lynx Edicions, Barcelona, 821 pp.

Taylor PB (1998) Rails: A Guide to the Rails, Gallinules and Coots of the World. Pica Press, Sussex, 600 pp.

Names and affiliations of submitters:

Rafael S. Marcondes, Louisiana State University

Luís Fábio Silveira, Universidade de São Paulo

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Comments from NACC members:

YES. But I would have appreciated a bit more analysis in the motion as to how the calls differed. They had fewer samples on xeno-canto on Rufous-naped.

YES. Here, the song differences are not learned.

YES. Vocal differences are huge and correlate with sharp morphological boundary.

YES. This seems pretty straightforward based on the large-scale vocal differences.

YES. The vocal differences and sharp parapatric changes in phenotype are very compelling.

YES. Although the plumage differences and the morphological differences are rather minor, the abrupt change argues for reproductive isolation. The vocalizations are so different and varied it makes you wonder what are homologous. There is a cut from NE Costa Rica on xeno-canto (XC140615), which should be albiventris, but sounds a bit more like cajaneus to me, but still it is quite different. The vocalizations provide in in the proposal (links to LNS) are staggeringly different.

YES. The vocal differences alone are convincing, but the parapatry with no sign of gene flow is the nail in the coffin. I think that a separate proposal is needed, however, on English names because retention of Gray-necked Wood-Rail for restricted A. cajaneus will cause confusion. We do not always follow the guideline of new names for all daughters from a split, but in cases in which we retain the parental name for one of the daughters, the asymmetry in range size is typically much greater than in this case (classic example is Red-shouldered and Red-winged blackbirds; counter-example that is too late to correct is California and Black-tailed gnatcatchers).

YES. The song differences are stunning, and corroborate well the sharp parapatric changes in phenotype.

Comments from Stiles: “A. YES. Near-parapatry plus morphological and vocal differences strongly favor recognizing albiventris as a separate species.

“B. Here, I'm on the fence.. given its much larger range, I wonder if we are better off conserving Gray-necked for cajaneus; Gray-cowled doesn't strike me as all that apt - it means gray-hooded, which seems not very appropriate for a long-necked bird like a rail! However, I could be persuaded.. Rufous-naped (or was it -capped?) seems OK for albiventris.”

Comments from Zimmer: “A. YES, for reasons already expressed by several members of both committees, i.e. plumage and vocal differences between the two groups are pronounced.

“B) YES”, even though I find myself choking out “Gray-cowled” every time I see cajaneus!

Comments from Areta: “A. YES. The marked differences in vocalizations in these highly vocal and duetting taxa with presumably genetically determined vocalizations argue strongly for the split. As a side note, this paper is a great example of how NOT to present spectrograms.

“[B. NO. I don´t see the need to change the English name of the southern taxon. It is a firmly entrenched and fairly good descriptive name. As Alvaro mentioned, “cowled” does not fit well with cajaneus.]

Comments from Claramunt: “YES. I don't see the morphometric “discontinuities”. There seem to be a difference in population MEANS but not a discontinuity. So, the evidence is not overwhelming; it reduces to a strong coincidence of vocalizations and a single plumage character. However, I think that that evidence is sufficient for accepting the change proposed.”

Comments from Robbins: “YES, for recognizing albiventris as a species. I did not appreciate how dramatically different the voices are between albiventris and cajaneus!