Proposal (19) to South American Classification Committee

Elevate Phacellodomus maculipectus to species rank

Effect on South American CL: this proposal would split Phacellodomus striaticollis (Freckle-breasted Thornbird) into two species, P. striaticollis and P. maculipectus.

Background: Two Phacellodomus taxa treated as subspecies in our baseline list have been treated as full species by recent authors, including Nores, Ridgely, and Whitney. One, striaticollis, is a lowland taxon found in thickets near marshes or other water (SE Brazil to EC Argentina), whereas the other, maculipectus, is an Andean forest bird (S Bolivia to NW Argentina). They are sufficiently similar phenotypically that their sister relationship has never been questioned, and they show a typical biogeographic among close relatives in that one taxon is southern Andean montane and the other is subtropical lowlands of S Brazil-N Argentina.

The taxonomic history of the two is as follows:

Cory & Hellmayr (1925) treated the two as conspecific, noting a half-dozen plumage differences between the two but making no further comment [These authors often treated taxa as full species that were lumped without comment by Peters.]

Peters (1951) followed this treatment, as did Meyer de Schauensee (1966, 1970) and Sibley & Monroe (1990).

Nores and Yzurieta (1981) treated the two as separate species citing differences in nest structure, voice, and iris color. Here's what they wrote:

"esta especie es considerada actualmente como una raza de P. striaticollis, sin embargo es lo suficientemente distinta para ser considerada especies, no sólo por sus características morfológicas, sino también por sus costumbres. En cuanto al color difiere de striaticollis, entre otras cosas, por tener las manchas pectorales más marcasa; flancos más oscuros; frente con rayas clara más conspicuas; e iris pardo en vez de amarillo. Una diferencia notable la constituye también el tipo de nido; en maculipectus es grande, trapezoidal y colgante del externo de una rama, a la manera de la mayoría de las especies del género, mientras que en striaticollis es pequeño, de forma esférica, algo alargado y apoyado a ramas o horquetas. En el canto existen también diferencias apreciables: mientras en maculipectus es fuerte, variado y casi siempre emitido a dúo con el otro integrante de la pareja, en striaticollis es suave, monótono, compuesto de una serie de silbos descendentes y generalmente emitido en forma individual."

Narosky and Yzurieta (1987) followed this treatment and repeated some of the evidence above.

Ridgely & Tudor (1994) followed this treatment, summarizing the evidence presented by Nores and Yzurieta. However, they stated: "our experience does not support their contention that the two taxa show marked vocal differences."

Whitney et al. (1994) also considered the two as separate species: "We consider montane, forest-based P. maculipectus to be a species distinct from widely disjunct P. striaticollis of the marshes of southeastern Brazil south to Prov. Buenos Aires, Argentina, following Narosky & Yzurieta (1987)."

Recommendation: Ideally, we'd all like to see quantitative documentation published for the differences in nest structure and voice. In fact, I like to think that one potentially beneficial outcome of our Committee deliberations will be to encourage publication of formal analyses. However, I think that the published anecdotal information is sufficient, in this case, to place "burden of proof" on those who would treat these as a single species. In fact, there may now exist more evidence for treating these Phacellodomus as species than for a number of pairs of allopatric Furnariidae taxa for which species rank has been maintained largely by tradition. So, I will vote YES on this one unless convinced otherwise by discussion looking forward to hearing what others think.

English name: Cory & Hellmayr used "Spotted-breasted", and this was followed by Whitney et al. Ridgely & Tudor used "Spot-breasted." "Freckle-breasted" has been used both for the broad and narrow striaticollis. Cory & Hellmayr used "Rufous-headed Thornbird" for nominate striaticollis. Discussion?

Lit Cit:

Narosky, T, & D. Yzurieta (1987) Birds of Argentina & Uruguay. Asoc. Orn. del Plata.

Nores, M., & D. Yzurieta. (1981). Nuevas localidades para aves argentinas. Historia Natural 2: 33-42.

Whitney, B. M., J. L. Rowlett, & R. A. Rowlett. (1994.) Distributional and other noteworthy records for some Bolivian birds. Bull. Brit. Ornith. Club 114: 55-61.

Van Remsen, 5 June 2002

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Comments from Stiles: "This kind of evidence seems convincing to me, though I would like to see direct comparison of sonograms along the Isler lines. Regarding English names, I have no opinion without having seen the birds! However, I suppose I might use this opportunity to indulge in airing one of my pet peeves. the use of Spot- instead of Spotted- (and similar constructions) when the meaning is "many spots" rather than "one spot". To me, spot-breasted implies the latter, spotted-breasted, the former and one loses a useful distinction by mixing the two (not a trivial matter with3000+ species to name...). In other words, the gain in "simplicity and euphony" does not compensate for the loss in precision (and where are "simplicity and euphony" in such monsters as Northern Chestnut-tailed Antbird?)"

Comments from Nores: "Si estoy de acuerdo con separar como especie a Phacellodomus maculipectus. Para mi es muy diferente de striaticollis y pienso que cantan distinto, a pesar de que Ridgely y Tudor dicen que el canto es igual."

Comments from Jaramillo: "Very much in favour of elevating maculipectus to species rank. I have had experience with both taxa in Argentina, Bolivia and Uruguay. They differ in voice, habitat, eye colour, details of plumage, nest structure etc. Descriptions of the nests of the two taxa, are found in Narosky, Fraga and de la Peña 1983. Nidificacion de las Aves Argentinas (Dendrocolaptidae y Furnariidae). Asociacion Ornitologica del Plata, Buenos Aires. The nest of Phacellodomus striaticollis is unlike that of most Phacellodomus in that it does not hang, but is supported from below by branches. In addition, the nest tends to be elongate. In its nest structure striaticollis is more similar to ruber than it is to maculipectus. I have a gut feeling that maculipectus and striaticollis may not even be sister species. With regards to the songs, I do have recordings of both but I am not sure where they are to make sonograms for the committee to see. The songs do differ from each other as much as songs of clearly unambiguously different species of Phacellodomus do. Contrary to Nores and Yzurieta 1981, I think that both will sing as duets at least some of the time. Perhaps striaticollis does it rarely, but I think it does duet (based on recollection, hopefully I have a tape somewhere)."