Proposal (206) to South American Classification Committee

 

Merge the hummingbird genus Schistes into Augastes

 

This proposal would lump two genera that have almost invariably been considered separate since their descriptions over 150 years ago. The first to formally recommend their lumping was apparently Ruschi (1963), but his recommendation received virtually no support until Schuchmann (1999) adopted this arrangement in HBW vol. 5, citing "external morphology and behavior" as justification.

 

Gould (1849) named the genus Augastes for the E Brazilian species scutatus and lumachellus. Both are distinctly marked with a brilliant green facial area and throat that ends posteriorly in a sharp point that bisects medially a sharply-defined, pale band across the lower border of the throat. The posterior underparts of scutatus are blue, of lumachellus, green; both have truncate to slightly forked, brilliant metallic tails in males - golden-green in scutatus, purplish-gold in lumachellus. The bill of Augastes, while slender and rather more pointed than in many genera, is not particularly remarkable.

 

In 1851 Gould erected the genus Schistes for albigularis and geoffroyi, (the former, the type of the genus, is now usually considered a subspecies of the latter), which show some strong similarities in plumage pattern to the species of Augastes but differ strikingly in bill morphology. The males of Schistes also have a brilliant green face and throat set off by black on the sides of the head and a white pectoral band, although there are also differences: the brilliant green is less extensive on the crown and does not end posteriorly in a point, the white postocular spot is larger and often extends back as a stripe, the tail is more rounded and with a broad blue subterminal band, there is a large patch of iridescent purple and blue (different from the color of the underparts) on the sides of the lower throat, etc. However, Gould separated Schistes ("to cleave") mainly because of its peculiar bill - rather short, extremely laterally compressed and needle-sharp at the tip. This bill is well suited to piercing flowers to rob nectar, which I have observed the species to do at flowers of Heliconia, Fuchsia, Palicoure, Tillandsia, and an Acanthaceae. In this respect, its bill resembles that of Heliothryx (also an inveterate nectar robber) but is even more extreme in its laterally compressed tip.

 

Ruschi (1963) advocated lumping Schistes into Augastes based upon three criteria: plumage, ecology and behavior. He presents (apparently from Gould's writings) detailed descriptions of the plumages in Augastes and Schistes including descriptions of females and young of each, noting the many similarities but not the differences and never once mentioning their very different beaks. The plumage similarities are undeniable, but given the frequent occurrence of convergences in plumage between unrelated or distantly related species in this family, such similarities are best treated with caution - especially when a clear morphological difference exists, in this case in the bill. 

 

Emphasizing that he had studied all three species in the field, Ruschi stated that the habitat of all three is "typical tropical arid regions having a climate characteristic of a semidesert".. he states that Schistes inhabits .."rocky fields or savannahs at altitudes of 1200 to 2700m, where the flowering plants include the Cactaceae, Caricaceae, Euphorbiaceae, Bromeliaceae and trees and bushes growing in rocky detritus". This statement is quite incredible since all accounts of the species in recent guides place this species in the interior of wet highland forests - this has certainly been my experience with geoffroyi, although albigularis not infrequently appears at forest edge or in old secondary woods as well. His descriptions of the habitat of the Augastes species are similar and such habitats occur on the Brazilian plateau where he apparently did study them - but I am extremely doubtful that Ruschi ever met Schistes in the field, especially as he never mentioned its flower-piercing habits. Ecologically, Augastes and Schistes are different birds.

 

Ruschi gives detailed descriptions of the displays of Augastes and Schistes, stating that they are essentially identical. It is difficult to know how much reliance to place on these descriptions: first, it is virtually certain that most of his observations of Augastes and all those on Schistes were made in captivity, where confinement might constrain the forms of many displays; and second, given the profusion of gross errors (if not outright fabrications) in many of his other publications (see Stiles 1995 on molt and Pacheco1995, Pacheco & Bauer s.f. on several other aspects), it would be ingenuous to accept any of Ruschi's statements at face value without independent confirmation. However, Schuchmann (1999) appears to do precisely this in citing Ruschi on this lumping (ironically, not citing the original paper but rather a general work). Given his tendency to make taxonomic decisions based mainly or exclusively on resemblances in plumage pattern (often ignoring other types of evidence), and his avowed intention to reduce the excessive number of hummingbird genera, Schuchmann may have followed Ruschi's arguments simply because they concurred with his own leanings.

 

To sum up, I do not feel that the available evidence gives a clear mandate for lumping Schistes into Augastes. Regarding external morphology, the similarities in plumage pattern must be set against a clear difference in bill form and there is no strong reason for preferring the former over the latter as a criterion. Ruschi«s ecological arguments are severely flawed (to say the least) and it is impossible to evaluate his behavioral arguments - given the unreliability of much of his published work, they should be confirmed before being accepted uncritically. In effect, evidence for lumping is certainly no stronger than the arguments for maintaining the genera separate (and thus, the status quo). Especially in the absence of genetic evidence, I would not favor lumping these two genera at present, and recommend a NO vote on this proposal.

 

References

Cory 1918

Meyer de Schauensee 1966

Pacheco 1995 O Brasil perde conco especies Atual. Ornitol. 66:7 (5pp.)

Pacheco & Bauer (s.f). A lista de aves de Espiritu Santo de A. Ruschi. Pp. 261-278 en Ornitologia y Conservacao: da Ciencia as Estrategias. 

Peters 1945

Ridgway 1911

Ruschi, A. 1963. Notes on Trochilidae: the genus Augastes. Proc. XIII Int. Ornithol. Congr. 141-146.

Schuchmann 1999. HBW, Vol. 5.

Stiles 1995, Auk 112:118-132.

 

F. Gary Stiles, February 2006

 

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Comments from Remsen: "NO, for the reasons outlined by Gary. Evidence for the merger is currently insufficient and highly tainted."

 

Comments from Stotz: "NO. I don't think that Ruschi can be trusted on any data. He is clearly wrong about Schistes habitat, although I'd agree with his characterization of Augastes habitat. That being said, the nature of plumage convergence is striking, and it is not impossible that Ruschi and Schuchmann are correct. But it is certainly premature to do this."

 

Comments from Zimmer: "NO. As Doug notes, there are some interesting parallels in plumage characters, but the habitat discussion by Ruschi is clearly incorrect for Schistes, and ecology and bill morphology of Schistes relative to the two species of Augastes actually argues against a merger. There is not enough evidence to overturn the status quo."

 

Comments from Robbins: "NO. Gary's analysis is right on and until we have genetic data to suggest otherwise, we should continue to recognize Schistes. Thus, I vote 'no'."

 

Comments from Silva: "NO. We cannot trust Ruschi's information. In fact, Augastes inhabits a special type of highland savanna termed in Brazil as "campos rupestres" (rough translation to English as "rocky fields") that is a incredible vegetation type with thousands of endemic plant species. I will never characterize this habitat as a "semidesert".

 

Comments from Pacheco: "NO. Evidentemente!! Diante das discrep‰ncias com a realidade, Ž muito poss’vel que Ruschi jamais tenha verdadeiramente "estudado Schistes em campo. Os resultados do "muito criativo Ruschi geralmente afrontam o bom senso e a inteligncia dos leitores melhor informados."

 

Comments from Nores: "NO. Pienso que los argumentos mostrados por Stiles dan una clara evidencia de que son distintos gŽneros. Yo tambiŽn opino que la informaci—n provista por Ruschi es muy poco confiable y deber’a s—lo ser tenida en cuenta cuando pueda verificarse, por ejemplo, con ejemplares depositados en museos."