Proposal (35) to South American Classification Committee
Split Furnarius cinnamomeus from F. leucopus
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 their history, the taxon cinnamomeus has been treated as s subspecies of Furnarius leucopus (Pale-legged Hornero). They are allopatric (nearly parapatric) taxa with no known contact zone; cinnamomeus is endemic to the Mara–on valley and western Peru and Ecuador, whereas leucopus is found east of the Andes. No published data exist on characters directly relevant to assessing potential interbreeding such as vocalizations; voices are described as being different, but analysis has not been published. The difference in iris color (pale in cinnamomeus, dark in leucopus) has potential as an isolating mechanism. They are 100% diagnosable phenotypic units based on plumage characters. The primary differences in plumage are (apparent) degree of pigment saturation, with cinnamomeus paler ventrally and duller, darker dorsally. There are no pattern differences. Cinnamomeus is significantly larger in body size. In my opinion, qualitatively, the plumage differences are less than those among the subspecies of F. rufus, and the difference in body size is substantially less. Cinnamomeus also differs less in plumage from leucopus than do sympatric F. leucopus and F. torridus.
Cory & Hellmayr (1925), Peters (1951), Meyer de Schauensee (1966, 1970), Vaurie (1980), and Sibley & Monroe (1990) treated them as conspecific. Parker & Carr (1992) treated them as separate species but I cannot find a discussion of the problem therein. Ridgely & Tudor (1994) continued to consider them conspecific, but noted that cinnamomeus and perhaps isolated longirostris of N Colombia and NW Venezuela may represent separate species. Ridgely & Greenfield (2001) recognized cinnamomeus as separate species. Hilty (2003) treated longirostris and cinnamomeus as separate species. Remsen (2003) maintained them as conspecific but noted that cinnamomeus almost certainly deserved species rank.
Analysis: This problem is like perhaps several hundred others in South America with respect to species-ranking of allopatric sister taxa: we don't have enough data to make a sound decision one way or another, but we need to deal with them. It would be reasonably easy to obtain vocal data on these and other Furnarius to do an analysis following the protocols established by Isler, Isler, & Whitney (1998), but that's for the future. The plumage differences are not really impressive to me, and not much more than among the some subspecies of leucopus itself (i.e., assimilis and tricolor from nominate leucopus). Although Ridgely & Greenfield mention vocal and behavioral differences between cinnamomeus and leucopus, they did not provide details.
There is also the problem of what to do with longirostris. Ridgely & Greenfield (2001) and Hilty (2003) also elevated it to species rank, and Hilty (2003) described the its song as differing from the others but did not make direct comparisons. Ridgely & Tudor (1994) thought that this taxon was closer to the nominate leucopus group than to cinnamomeus; longirostris also has a dark iris like nominate group. If this proposal passes, then we need to consider longirostris in a subsequent proposal.
Recommendation: I will vote "NO" on this proposal because in the absence of published data, I see no reason to change our current classification. I strongly suspect that Ted Parker, Bob, Steve Hilty, and others are correct in elevating cinnamomeus to species rank, but until some sort of data are published, I think we should remain conservative.
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.
MEYER DE SCHAUENSEE, R. 1966. The species of birds of South America and their distribution. Livingston Publishing Co., Narberth, Pennsylvania.
MEYER DE SCHAUENSEE, R. 1970. A guide to the birds of South America. Livingston Publishing Co., Wynnewood, Pennsylvania.
PARKER, T. A. III & J. L. CARR (eds.). 1992. Status of forest remnants in the Cordillera de la Costa and adjacent areas of southwestern Ecuador. Rapid Assessment Working Papers 2. Conservation International, Washington, DC, 172 pp.
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 does not pass, then I'll work on another one on the English names of these two.
Comments from Schulenberg: "My vote: "No". I do strongly suspect that cinnamomeus and leucopus are separate species. The close approach in distribution, with "coastal" cinnamomeus entering the Maranon but showing no known approach to nearby leucopus in characters, looks a lot like two biological species. But no one seriously has examined the situation either. In the Peru book I'd prefer to recognize one species, with some hand-waving that more than one species may be involved. "
Comments from Robbins: "Yes, plumage and descriptions of voice indicate they deserve specific rank; so, lets deal with longirostris."
Comments from Stotz: "I vote to split Furnarius cinnamomeus from leucopus. There are vocal differences, and Remsen (2003) admitted that cinnamomeus is almost certainly a distinct species, while maintaining them as conspecific. The taxon longirostris complicates the issue; it probably should be split, but it not directly addressed in the proposal."
Comments from Zimmer: "I'm really on the fence on this one, and could easily go either direction. I believe the split of F. r. cinnamomeus is valid: the combination of a different eye color (which seems a likely isolating mechanism), combined with observed vocal differences and a geographic distribution that fits a known biogeographical pattern of species replacement, all screams out at me to support the split. However, there has been no published analysis of the vocal differences that I recognize in the field, and as a general rule I support Van's philosophy of a "minimum standard". Were that the only problem, I'd probably still vote to split. However, I think the entire species complex is in need of review. Besides the question of longirostris, I've also noted vocal differences between Amazonian populations and assimilis of eastern/central Brazil. Granted, I don't think either the vocal differences or morphological differences are as great as between cinnamomeus and the rest of the complex. However, in the absence of a published analysis, I kind of hate to make piecemeal species-limits changes within the complex until we have a better understanding of the entire picture (witness the 1994 Ridgely treatment of Thamnophilus punctatus as a simple cis/trans Andean split prior to this Isler et al paper documenting a much more complex situation). Record me as a somewhat reluctant "no" on this one."
Comments from Stiles: "NO (again, until evidence is published)."
Comments from Silva: "Yes. Taking in account the plumage differences and the geographical distribution, I think we have a good case to recognize these two taxa as distinct biological species."
Comments from Jaramillo: "NO. While I am convinced that there are more than two species involved here, I worry that there is no published data on vocalizations, and no analysis that decides if 1, 2, or 3 species are involved. This problem needs to include longirostris, and vocal data."