Proposal (170) to South American Classification Committee

Lump Topaza pyra into Topaza pella

This proposal would lump two forms considered species in our baseline list and most literature, following the treatment in HBW based upon Schuchmann (1982).

Topaza pella and T. pyra are two large, spectacular, strongly sexually dimorphic hummingbirds that had been treated as separate species by virtually all authors until Schuchmann (1982) lumped them. Schuchmann's arguments were based upon overall morphological similarity and distribution -- in particular, he considered that the range of pyra effectively filled in the gap between the main population of pella in NE South America and an apparently isolated population in NE Ecuador, such that the combining of the two would produce a single continuous distribution over the entire region. This lumping was followed by Ruschi (1986) and repeated by Schuchmann (1999), who stated that "morphologic differences are of a subspecific level" and cited occasional individuals of pella with orange ventral coloration more typical of pyra.

Hilty & Brown (1986) dissented, considering that the distributional picture suggested overlap of the two in E Ecuador, favoring species status for both. Sibley & Monroe (1990) argued likewise but placed both forms in a single superspecies. Hu et al. (2000) presented a detailed case for treating the two as separate species, and this determination was followed by Ridgely & Greenfield (2001) and Hilty (2003). Thus, the question of species limits boils down to a comparison of the arguments of Schuchmann (1982, 1999) and Hu et al. (2000).

Hu et al. (2000) presented an extensive discussion of morphology based upon examination of very large series covering the known distributions of both forms. They included the first detailed description of the plumages of T. pyra and a reinterpretation of the plumage sequence of T. pella; these are probably the most complex sequences known in the Trochilidae. They found that overall, pyra was significantly shorter-billed than pella (even when the short-billed race microrhyncha of the latter was included) but longer-winged, and averaged longer-tailed and heavier, sex for sex, as well. They listed seven plumage characters that were diagnostic for distinguishing males of pyra from those of pella, and three for females, as well as another dozen or so features in which the two forms showed strong average differences, but which were not fully diagnostic (among which was the belly colors of males mentioned by Schuchmann).

As for distribution, Hu et al. (2000) presented convincing evidence that the supposed Ecuadorian population of pella (described as a separate subspecies, panprepta), separated by 1500 km from other populations of pella, was based on mislabeled specimens of Cayenne origin. This at once renders irrelevant arguments both for and against species status of pyra based on complementarity of distributions (Schuchmann, against) or sympatry (Hilty & Brown, for). They demonstrated that the two forms are nowhere sympatric by current information, but do approach each other closely in eastern Venezuela (<100 km); the distributions in NW Brazil are too poorly known to form firm conclusions but in general pyra occurs NW of pella in this broad region. More importantly, the morphological differences between the two hold constant throughout their distributions: there is no tendency for individuals of the two forms closest geographically to be most similar morphologically.

My general conclusion from this review of the evidence is that the study of Hu et al. is much more detailed and thorough, and clearly trumps that of Schuchmann both as regards morphology and distribution. I therefore strongly advocate a NO vote on this proposal.

REFERENCES

Hilty 2003: Guide to the birds of Venezuela

Hilty & Brown 1986: Guide to the birds of Colombia

HU, D.-S., L. JOSEPH, & D. AGRO. 2000. Distribution, variation, and taxonomy of Topaza hummingbirds (Aves: Trochilidae). Ornitologia Neotropical 11: 123-142.

Ruschi, A. 1986.

Ridgely & Greenfield 2001, Guide to the birds of Ecuador.

SCHUCHMANN, K.-L. 1982. Zur Biologie des Königskolibris (Topaza pella). Trochilus 3: 57-61.

Schuchmann, K-L. 1999. HBW, vol. 5.

Sibley & Monroe, 1990. Distribution and taxonomy of birds of the world.

F. Gary Stiles, March 2005

Comments from Remsen: "NO. Published evidence clearly favors species rank for both."

Comments from Zimmer: "NO. As Gary has clearly laid out, the available data makes a much stronger case for maintaining the two forms as separate species."

Comments from Robbins: "NO. Gary's review of this clearly indicates that we should continue to recognize these as species. Thus, I vote "no" for lumping the two Topaza."

Comments from Pacheco: "NO. Diante dos resultados em Hu et al. e dos comentários de Stiles, a reunião de Topaza pella e T. pyra torna-se implausível."

Comments from Jaramillo: "NO - available evidence is strong for keeping the two as separate species."

Comments from Nores: "NO. Los argumentos de Hu et al. son mucho más convincentes que las razones dadas por Schuchmman. Además, con sólo mirar los dibujos que aparecen en el HBW uno ya se da cuenta que son diferentes especies. De todos modos, habrá que esperar estudios moleculares para ver cómo es la situación real."