Proposal (198) to South American Classification Committee

 

Transfer Philydor dimidiatum (Furnariidae) to the genus Syndactyla

 

The following proposal is based on the recently published paper (and references therein) by Robbins and Zimmer (2005). A pdf of the paper is available from either author: (mrobbins<at>ku.edu; kjzsrz<at>csn.net).

 

Background: Generic relationships of the many foliage-gleaners comprising the philydorine assemblage have long been disputed. Vaurie (1980) recommended an expanded concept of the genus Philydor  that included, among many others, the currently recognized genera Syndactyla and Simoxenops.  Although Vaurie's views failed to gain wide acceptance, the generic placement of some foliage-gleaners has shifted between Syndactyla and other genera, suggesting that characters used to separate these genera are not well defined. The taxon Syndactyla mirandae was described from Goiás, Brazil, and for a time was treated as a subspecies of S. rufosuperciliata before it was determined to be a synonym of P. dimidiatum (Remsen 2003). More recently, Syndactyla ruficollis, although divergent in plumage characters from the three recognized species of Syndactyla, was transferred to that genus from Automolus, based largely on striking similarities in vocal characters (Parker et al. 1985, Ridgely & Tudor 1994).

 

Vocal characters may provide the strongest argument for the relatedness of dimidiatum to Syndactyla and for the separation of this species from the currently recognized Philydor. Loudsongs of the three Syndactyla species represented in our inventory were remarkably uniform in pattern and note quality. Calls of these species were also strikingly similar to one another. Indeed, the vocalizations of all three species are so similar that they are easily confused by the uninitiated listener. All are united by the harsh, nasal quality of their notes (both in loudsongs and in calls), the accelerating pattern of the loudsong, the often stuttering start to the loudsong, and the variation in loudsong length, changes of pace and frequency shifts displayed by individuals, particularly in response to playback. In describing vocalizations of the various members of the genus, Ridgely & Tudor (1994) employed 'a distinctive accelerating series of harsh nasal notes, stuttering at first' for subalaris, and 'a series of harsh, nasal, ratchety notes which starts slowly and then speed up' for ruficollis. Although the fourth currently recognized species in the genus, S. guttulata, was not represented in our sample, published descriptions of its vocalizations are consistent with those of the other members of the genus. Hilty (2003) described the song of guttulata as 'a harsh, accelerating 'cjak, cjak, czak, czak-zak-zak-zak-za-za-za', sometimes followed by a few more notes', and the call as 'a harsh, rough 'chak'.' Ridgely & Tudor (1994) likened the vocalizations of guttulata to those of subalaris.

 

The vocalizations of P. dimidiatum are strikingly similar to those of the four other Syndactyla. They have the same harsh, nasal quality to the calls and to the individual and collective notes of the loudsongs. The loudsongs typically commence with a stuttering preamble, and they show much variation in length, pace changes and frequency shifts from one song to the next in the same individual. Both Simoxenops share these vocal characters. The vocal similarities between Simoxenops and Syndactyla were first noted by Parker (1982), and have been echoed by subsequent authors (Parker & Bates 1992, Ridgely & Tudor 1994, Remsen 2003).

 

Conversely, the vocalizations (particularly the loudsongs) of P. dimidiatum are not noticeably similar to those of any of the other recognized species of Philydor, none of which shares the distinctive nasal quality that immediately distinguishes dimidiatum, Syndactyla and Simoxenops. More important, perhaps, is that our samples of other Philydor species (with the exception of P. pyrrhodes) showed no evidence of the capacity for individual variation in songs and calls that typifies P. dimidiatum, a seemingly ubiquitous feature of vocalizations of the various species of Syndactyla and Simoxenops. The other Philydor species respond to playback by giving songs and calls indistinguishable from natural (unsolicited) vocalizations, whereas dimidiatum, Syndactyla and Simoxenops display complex repertories that involve numerous permutations of the natural vocalizations depending on their overall degree of agitation. Also in contrast to Syndactyla and Simoxenops, the genus Philydor does not display great uniformity in loudsongs, and almost none in calls.

 

In all of its vocal characters and in its distinctly upturned mandible, P. dimidiatum is much more like all of the currently recognized species of Syndactyla than any currently recognized species of Philydor. In plumage characters, it is closest to Simoxenops ucayalae, but is also similar to Syndactyla ruficollis in having some flammulation on the underparts but lacking true streaking. Moreover, behaviorally, dimidiatum is also a closer fit with Syndactyla and Simoxenops in gleaning primarily from branch or vine surfaces, employing hammering or chiseling motions of the bill, and in often foraging apart from mixed-species flocks. The hammering or chiseling of substrates has been noted for S. guttulata, S. rufosuperciliata (Remsen 2003) and S. ruficollis (KJZ unpubl.), and is a primary search maneuver of both species of Simoxenops (Parker 1982, Remsen & Robinson 1988, Parker & Bates 1992, Kratter & Parker 1997, Zimmer et al. 1997). Conversely, this behavior is rare (at best) or absent in Philydor, most species of which are dead-leaf specialists (Remsen 2003). Although all Syndactyla species regularly associate with mixed-species flocks, they are less habitual in their attendance than are Philydor, most of which are inveterate members of such flocks, and are rarely encountered away from them (pers. obs.; Remsen 2003).

 

Taxonomic recommendation: We recommend that 'Philydor' dimidiatum be placed in the genus Syndactyla; the name would thus become Syndactyla dimidiatum (Pelzeln). This change dictates the modification of Philydor dimidiatum to Syndactyla dimidiata, as the specific name is a variable adjective in a new combination with a feminine genus (S. M. S. Gregory in litt. 2004, N. David in litt. 2004). A molecular-based phylogeny is required to confirm our hypothesis. If this proposal passes a separate proposal will deal with the relationship of Syndactyla and Simoxenops.

 

References:

 

Kratter, A. W. & Parker, T. A. 1997. Relationship of two bamboo-specialized foliage-gleaners: Automolus dorsalis and Anabazenops fuscus (Furnariidae). Pp. 383-397 in Remsen, J. V. (ed.). Studies in Neotropical ornithology honoring Ted Parker. Orn. Monogr. 48.

Parker, T. A. 1982. Observations of some unusual rainforest and marsh birds in southeastern Peru. Wilson Bull. 94: 477-493.

Parker, T. A. & Bates, J. M. 1992. Rediscovery of the Bolivian Recurvebill with notes on other little-known species of the Bolivian Andes. Wilson Bull. 104: 173-178.

Parker, T. A., Schulenberg, T. S., Graves, G. R. & Braun, M. J. 1985. The avifauna of the Huancabamba region, northern Peru. Pp. 169-197 in Buckley, P. A., Foster, M. S., Morton, E. S., Ridgely, R. S. & Buckley, F. G. (eds.) Neotropical ornithology. Orn. Monogr. 36.

Ridgely, R. S. & Tudor, G. 1994. The birds of South America, vol. 2. Univ. of Texas Press, Austin.

Remsen, J. V. 2003. Family Furnariidae (ovenbirds). Pp. 162-357 in del Hoyo, J., Elliott, A. & Christie, D. A. (eds.) Handbook of the birds of the world, vol8. Lynx Edicions, Barcelona.

Remsen, J. V. & Robinson, S. K. 1988. A classification scheme for foraging behavior of birds in terrestrial habitats. Pp. 144-160 in Morrison, M. L., Ralph, C, J., Verner, J. & Jehl, J. R. (eds.) Avian foraging: theory, methodology and applications. Stud. Avian Biol. 13.

Robbins, M. B. & K. J. Zimmer. 2005. Taxonomy, vocalizations and natural history of Philydor dimidiatum (Furnariidae), with comments on the systematics of Syndactyla and Simoxenops. Bull. Brit. Ornith. Club 125:212-228.

Vaurie, C. 1980. Taxonomy and geographical distribution of the Furnariidae (Aves, Passeriformes). Bull. Amer. Mus. Nat. Hist. 166.

Zimmer, K. J., Parker, T. A., Isler, M. I. & Isler, P. R. 1997. Survey of a southern Amazonian avifauna: the Alta Floresta region, Mato Grosso, Brazil. Pp. 887-918 in Remsen, J. V. (ed.) Studies in Neotropical ornithology honoring Ted Parker. Orn. Monogr. 48.

 

Mark Robbins & Kevin Zimmer , December 2005 

 

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Comments from Silva: "NO. Although Robbins & Zimmer presented quite a lot of evidence from morphology and vocalization, this information has not been evaluated within a phylogenetic framework. I will be a bit conservative on this proposal and vote NO. I would prefer to wait for a detailed phylogenetic study of these genera to support any change in this specific group of Furnariidae."

 

Comments from Stiles: "YES. A number of Vaurie's taxonomic decisions in the Furnariidae, made without the slightest experience with the birds outside of museum trays, have come up wanting and this seems to be another of them. As in several other cases, the vocalizations and natural history of many species are only now becoming known, enabling a reevaluation of the often flimsy or conflicting morphological evidence - especially in a family notorious for its very limited diversity in plumage color and pattern. Although it would be nice to have solid genetic evidence, my feeling is that the data on voice, behavior and morphology presented here trumps previous taxonomies based on information much weaker and less varied. Unless and until genetic data dictate otherwise, I see no reason not to follow the best available evidence when this represents a significant advance in knowledge."

 

Comments from Nores: "NO, aunque no muy convencido. La especie dimidiatus es mucho más parecida a Philydor que a Syndactyla. Todas las especies de Syndactyla son rayadas y tienen un plumaje más pardo, mientras que todas las especies de Philydor, incluyendo dimidiatus, son mayormente lisos y rufos. De pasar dimidiatus a Syndactyla, se estaría aceptando que una de las principales características del género Syndactyla (tener plumaje rayado y ser mayormente rufo) no sería importante. Lo de las vocalizaciones parece muy razonable lo mismo que lo del pico, pero en casos como éste que por el canto pertenecería a un género y por la coloración a otro, sería mejor esperar otro tipo de evidencia (molecular, por ejemplo) para tomar una resolución final."

 

Comments from Pacheco: "NO. Concordo com a proposićčo a partir da minha experiźncia em campo com os táxons brasileiros dos Phylidorinae. Uma correćčo. A sinomimizaćčo de Syndactyla mirandae com Philydor dimidiatum foi anunciada originalmente por F. C. Novaes (1953) Sobre a validade de "Syndactyla mirandae (Snethlage, 1928) (Furnariidae, Aves) Rev. Bras. Biol. 14(1):75-76."

 

Comments from Jaramillo: "YES - As Gary says, this is the best available evidence thus far on how to deal with this species. I am comfortable transferring dimidiatum to Syndactyla based on this evidence, particularly the vocalizations."