Proposal (41) to South American Classification Committee

Split Phacellodomus inornatus from P. rufifrons

Effect on South American CL: This proposal would elevate a taxon to species rank that we currently treat as a subspecies on our baseline list.

Background: For most of its history, Phacellodomus rufifrons (Rufous-fronted Thornbird) has been considered to be a single, polytypic species, e.g., Cory & Hellmayr (1925), Peters (1951), Meyer de Schauensee (1970), Vaurie (1980), Hilty & Brown (1986), and Sibley & Monroe (1990). Below is the classification I used in HBW (Remsen 2003):

P. r. inornatus Ridgway, 1888 - NC Venezuela (Yaracuy, Carabobo, SE Falcón east to Miranda).

P. r. castilloi Phelps & Aveledo, 1987 - NE Colombia (Boyacá, Arauca, Casanare, Vichada, NE Meta) and W and C Venezuela (Lara, Barinas, and Apure west to Sucre and Monagas).

P. r. peruvianus Hellmayr, 1925 - upper Marañon Valley of N Peru (Amazonas, Cajamarca, San Martín) and extreme S Ecuador (S Zamora-Chinchipe).

P. r. specularis Hellmayr, 1925 - NE Brazil (Pernambuco).

P. r. rufifrons (Wied, 1821) - E Brazil (S Maranhão, S Piauí, Bahia, N Minas Gerais).

P. r. sincipitalis Cabanis, 1883 - E Bolivia (Beni, Santa Cruz, Tarija), S Brazil (S Mato Grosso), NC Paraguay, and NW Argentina (Jujuy, Salta, Tucumán).

Although quantitative data are lacking, each of the six subspecies may be 100% diagnosable based on plumage characters. Nevertheless, most differences are relatively minor, mainly involving plumage tone. The two biggest differences are (1) inornatus and castilloi, the two northern taxa, lack the rufous forecrown that the other four have, and (2) specularis of extreme NE Brazil has a unique rufous patch in its primaries.

Ridgely & Tudor (1994) hinted that more than two species might be split from rufifrons (inornatus + castilloi; peruvianus) but did not provide details. Ridgely & Greenfield (2001) considered inornatus (with castilloi) to represent a separate species, based on plumage, disjunct distribution, and voice. No details on the latter, however, were reported, and I cannot find any published comparisons, event qualitative, much less a formal analysis. Hilty (2003) followed this treatment, and stated that "Some unite all widely disjunct forms ... into a single sp. ...", thus unfortunately implying that the recent data-free split had a long history and consensus; Hilty (2003) also stated that "Taxonomy here follows Sibley and Monroe [1990]", thus also unintentionally but unfortunately suggesting that the species split dates back at least that far; what Hilty presumably intended to state was that his subspecies-level taxonomy followed Sibley-Monroe.

Analysis: There are no published data on which to base a decision to split P. rufifrons into two or more species. The presence/absence of a forehead patch is the only "quantum" character known so far to separate the inornatus group from the nominate group. There is almost as much geographic and individual variation in presence/absence of this character in another furnariid, Synallaxis albescens, which is currently treated as a single polytypic species. Furthermore, a "quantum" difference also exists in plumage characters between Phacellodomus r. specularis and the rest of the subspecies, and I see no immediate reason why that difference is not accorded equal weight. Vocalizations may indeed differ between the inornatus group and the rest, but the data need to be published and analyzed (and to include peruvianus of the Marañón and specularis) before a taxonomic change is made, in my opinion. The most intriguing observation that I know potentially relevant to species limits is that at least one case of nest-helpers has been reported from the understudied Brazilian population, and this has not yet been reported in the much more thoroughly inornatus group (reasonably thorough studies by Skutch, Thomas, and Lindell).

Recommendation: I will vote "NO" on this proposal not because I don't think that more than one species could be involved, but because the published data to date are insufficient for making any changes from status-quo taxonomy.

Literature Cited:

CORY, C. B., AND C. E. HELLMAYR. 1925. Catalogue of birds of the Americas Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13, pt. 4.

HILTY, S. L. 2003. Birds of Venezuela. Princeton University Press, Princeton, New Jersey.

HILTY, S. L., AND W. L. BROWN. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey.

MEYER DE SCHAUENSEE, R. 1970. A guide to the birds of South America. Livingston Publishing Co., Wynnewood, Pennsylvania.

PETERS, J. L. 1951. Check-list of birds of the world, vol. 7. Museum of Comparative Zoology, Cambridge, Massachusetts.

REMSEN, J. V., JR. 2003 (in press). Family Furnariidae (ovenbirds). Pp. #-# in "Handbook of the Birds of the World," Vol. 8. Broadbills to Tapaculos (del Hoyo, J. et al., eds.). Lynx Edicions, Barcelona.

RIDGELY, R. S., AND G. TUDOR. 1994. The birds of South America, vol. 2. Univ. Texas Press, Austin.

RIDGELY , R. S., AND P. J. GREENFIELD. 2001. The birds of Ecuador. Vol. I. Status, distribution, and taxonomy. Cornell University Press, Ithaca, New York.

SIBLEY, C. G., AND B. L. MONROE, JR. 1990. Distribution and taxonomy of birds of the World. Yale University Press, New Haven, Connecticut.

VAURIE, C. 1980. Taxonomy and geographical distribution of the Furnariidae (Aves, Passeriformes). Bulletin of the American Museum of Natural History 166: 1-357.

Van Remsen, July 2003

P.S.: If the proposal passes, then I'll work on another one on the English names of these two.

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Comments from Schulenberg: "My vote is "No". It hardly would surprise me if more than one species were involved, but it would be nice to have a proper analysis on which to hang one's decision. 

"I was a little surprised, in reading Van's summary, to read that "this [helpers at the nest] has not yet been reported in the much more thoroughly inornatus group (reasonably thorough studies by Skutch, Thomas, and Lindell)." I thought that this behavior *was* known from Venezuela. I reached for what was handy, a copy of Skutch's 1969 Wilson Bulletin paper. He observed helpers in nest building, but not in feeding of the young. This surprised him, and he commented (page 37): "I have little doubt that, with more opportunities to watch nests with three or more grown occupants while they held nestlings, I should have found helpers attending the young." So, was he just letting his expectations (that there would be helpers) get the best of him? Or do helpers indeed occur in inornatus? I haven't looked at any papers by Thomas or Lindell, so I don't know if their observations were more extensive than Skutch's (i.e. sufficiently more extensive to refute Skutch's earlier speculations). "

Remsen response: “The technical definition of "helpers" currently restricts its use to those individuals known to contribute to the feeding off nestlings or other direct assistance to them. Skutch used a looser definition (and many other furnariids have similar cases of young of the year adding material to active nests of their parents and so on). Thomas and Lindell were unable to detect any examples of "true" nest helpers (in contrast to the more limited work in Brazil), and neither was Skutch.  Small "N" of course does not inspire confidence, but the same could be said in terms of the proposed vocal differences among the taxa involved.”

Comments from Stotz: "Leave as is. This is one where my attempt to do the "right" thing falls apart. I think that there are multiple species here, but Van is right--there is so little published information that you can't make even the slightest attempt to figure out what to do with specularis, and the vocal information is too vague to make any attempt to join together taxa. The best treatments seem to be one species or four, and it seems premature to go with four. I think my philosophical clarity falls apart on this one. "

Comments from Robbins: "I vote "NO" for proposal 41 because of the lack of vocal data."

Comments from Zimmer: "Another tough one. I really believe that P. inornatus should be split from rufifrons. There are real vocal differences between the two groups (much more so than any differences I've noted between Marañon populations or NE Brazilian populations and the rest of the southern rufifrons group). Combined with the discrete character difference of forehead color and a major range disjunction, I think that the two groups are different at the species level. Once again however, we're talking about vocal differences that fall within the realm of my field experience, but which have not been analyzed or even really talked about in the literature. In the interest of maintaining some "minimum standard" for change, I reluctantly vote "no" until such time as someone publishes some justification that includes at least a minimal discussion of vocal differences."

Comments from Stiles: "NO until evidence is up front, as in many other cases."

Comments from Silva: "No. I believe that several biological and phylogenetic species are involved. Thus, I would prefer to see a study formally splitting the evolutionary unities based on morphology, behavior and voice."

Comments from Jaramillo: "NO Certainly more than one species involved here, but how many? The lack of published vocal data, and or analysis makes this an impossible one to do anything with based on present available information."

Comments from Whitney: "While I certainly empathize with Doug's arguments, I still think Van's position is the better one for the SACC. If, however, the SACC one day decides to do all of this splitting (and there is a huge amount that can be "justified" in the minds of the SACC), then it will be necessary to provide highly detailed statements of range for each species."