Proposal (302) to South American Classification Committee
Recognize Eriocnemis isabellae as a species
This proposal would add a species to the SACC list, Eriocnemis isabellae (Gorgeted Puffleg) Cortés-Diago, Ortega, Mazariegos-Hurtado & Weller 2007.
This new taxon occupies an extremely limited range on the Serranía del Pinche, a small outlying spur of the Western Andes in Cauca Department, southwestern Colombia. It shows a unique combination of characters in the genus, in part effectively combining certain features of E. vestita and E. nigrivestis. The males resemble those of nigrivestis in their overall black coloration (if anything, the breast is even blacker - velvety black with no faint green highlights); in both the center of the gorget is flashing violet but in isabellae the sides of the gorget are broadly brilliant, flashing green whereas in nigrivestis these areas are dull, dark green with a blackish "veiling" similar to the rest of the head and not at all conspicuous; the nape and upper back of nigrivestis show a distinct bronzy gloss absent in isabellae, in which the nape is greener and the upper back nearly as black as the breast. In both, the lower back and rump are brighter green, passing abruptly to dark steel-blue (isabellae) or violet-blue (nigrivestis) on the upper tail-coverts and central rectrices; in both, the lower tail-coverts are flashing violet (perhaps more brilliant in isabellae compared to our one nigrivestis. In size, isabellae is decidedly smaller (wings of all three male isabellae are more than 3 mm shorter than that of our one male nigrivestis); there is no overlap in bill lengths and very little if any in tail lengths in the data given in the original paper and the tail appears to be more deeply forked in nigrivestis. I have seen no females but the description states that those of isabellae are more similar to those of vestita than to those of nigrivestis in having extensive rufous fringes and turquoise reflections on the abdomen. The authors recommend considering all three as members of a superspecies. I should note that the isolated race paramillo of E. vestita (at the N end of the Western Andes) is also much darker than nominate vestita of the Eastern Andes, showing in this and its slightly smaller size an approach to nigrivestis and isabellae. My personal opinion, having specimens of all of these before me, is that isabellae is best treated as a species: I am especially impressed by the very striking difference in the malesę gorgets, which could easily act as a factor influencing female choice (and hence, as an isolating mechanism) were isabellae to come into contact with either of the other species. The size differences are also striking. Differences of similar magnitude define species in some other Andean genera (e.g., Heliangelus, Metallura). As isabellae is completely diagnosable, species status by a phenetic criterion (the "phylogenetic species concept") is also applicable. Hence, I recommend a YES vote on this proposal.
Cortés-Diago, A., L. F. Ortega, L. Mazariegos-Hurtado and A.-A. Weller. 2007. A new species of Eriocnemis (Trochilidae) from southwest Colombia. Ornitologia Neotropical 18:161-170.
Schuchmann, K.-L. 1999. Trochilidae. HBW, vol. 5.
F. Gary Stiles, August 2007
Note added by Stiles: One tiny thing I noticed on the Eriocnemis vestita paramillo specimen (and forgot to include in the proposal) is that the sides of the throat are also brilliant green as in isabellae, although they do not form a clear-cut gorget in the same way ... another reason to consider that vestita, nigrivestis and isabellae form a unit - given species limits in Eriocnemis and other Andean genera, the superspecies level seems best.
Comments from Remsen: "YES. Having just had the privilege of examining the specimens, including the type, under Gary's care, I am convinced that this taxon merits species rank, for all the reasons listed by Gary above. Especially impressive is the unique gorget pattern."
Comments from Jaramillo: "YES - The photos of the bird are neat! Reading the paper and proposal it does seem clear that this forms a superspecies with vestita and nigrivestis."
Comments from Robbins: "YES, based primarily on Gary's recommendation."
Comments from Nores: "YES. Aunque la coloración que puede verse en una foto que aparece en Internet http://www.thc-fc.org/PDF/EisabellaeBLENG.pdf y la distribución geográfica sugieren de que se trata de una subespecie de nigrivestis, más que de una especie. Por supuesto, quienes han podido ver los ejemplares y opinan que es una especie tienen muchos más elementos que yo para opinar, por eso voto que SI."
Comments from Cadena: "A tentative YES. This is a difficult one in principle: why is this not a subspecies of E. nigrivestis? To be consistent with the rationale we often follow to rank allopatric populations, it would be good to know how do the differences between this taxon and E. nigrivestis compare to differences between accepted subspecies and species in the genus (Gary?). Even then, the only real clincher in my opinion would be a phylogenetic (molecular) analyses that shows this taxon to be more allied to vestita than to nigrivestis, which would appear unlikely. With all this said, I think I will be a bit liberal in this case. Clearly, isabellae and nigrivestis are isolated populations that are most likely on completely independent evolutionary trajectories given their distributions, so I am confident in calling them different species especially considering that this is what the hummingbird experts have recommended."