Proposal (1058) to South American Classification Committee

Treat the spodionota subspecies group as a separate species from Silvicultrix frontalis.

Effect on SACC: This would split an existing species on the SACC list into two species.

Introduction: SACC has been asked to do this proposal because the IOC list treats them as two species, citing Moreno et al. (1998) for support. However, they are treated as conspecific by Clements, Howard-Moore, and HBW-BLI lists. I did not have this issue on our proposal “do list” because it is based largely on Moreno et al.’s comparative genetic distance using mtDNA sequence data (350 BP ND2).

Our current SACC note reads:

120. García-Moreno et al. (1998) suggested that the plumage and genetic differences between the frontalis and spodionota subspecies groups warranted species-level recognition for each.

Background: Silvicultrix (ex-Ochthoeca) frontalis has traditionally been treated as a single species that occurs in the humid Andes from n. Colombia to c. Bolivia, e.g., from Cory & Hellmayr (1927) through Meter de Schauensee (1970) and Fjeldså & Krabbe (1990) to AviList (2025), with 3-5 subspecies:

• albidiadema: Eastern Andes of Colombia

• frontalis: Central Andes of Colombia south to western Andes in n. Ecuador, but see next:

{• orientalis}: Eastern Andes from n. Ecuador to c. Peru (subsumed by Traylor [1985] into nominate frontalis)

• spodionota: Eastern Andes in c. Peru (Junín to n. Cuzco) but see next:

{• boliviana}: curiously patchy and taxonomically “impossible” range, interrupted by spodionota: Andes from c. Peru south to c. Bolivia; see Traylor (1985) for full details on this taxonomic conundrum, but briefly, recognizing boliviana splits it into two allopatric and evidently phenotypically indistinguishable populations, but treating this as a synonym of spodionota makes the latter split into 3 populations with a leapfrog pattern of phenotypic variation, the central one diagnosably different from the populations to north and south; then, there is also the unnamed Cordillera Vilcabamba population, which according to Traylor is the most distinctive of all with most individuals without wingbars … like the frontalis group. Broadly defined spodionota would thus be just as uncomfortable as recognizing disjunct populations of boliviana as the same taxon in that it would have four diagnosable populations, each possibly a PSC species. This one will be exceptionally interesting to study genetically.

Traylor (1985) provided rationale for their treatment as conspecific pending study of the contact zone in central Peru.

Below is John Fitzpatrick’s plate from Traylor (1985 – the original is much better than reproduced here). I have blacked out Silvicultrix pulchella to reduced noise, but I have left in the taxon jelskii of the western Andes of extreme s. Ecuador and nw. Peru; currently treated as a separate species, it has been treated as a subspecies of both S. frontalis and S. pulchella. Harvey et al. (2020) showed that it is sister to S. pulchella, not S. frontalis/spodionota.

New information: Obviously not very new but García-Moreno et al. (1998) in a study of the phylogeny of chat-tyrants used 320 bp on mtDNA (ND2) to produce the following phylogenetic hypothesis:

This was 1998, so cut them a lot of slack on the weak genetic sampling – this was top-of-the-line stuff back then. They showed that frontalis and spodionota groups were sister taxa with modest support. García-Moreno et al. (1998) argued for their treatment as separate species based on comparisons of relative genetic distance, including alluding to broader comparisons of many taxa of Andean forest birds.

As noted by Traylor (1985) and García-Moreno et al. (1998), the putative contact zone between the northern frontalis group and the southern spodionota group is somewhere in that 150 km long region of Dpto. La Libertad from which there are almost no bird samples and in which there are no known biogeographic boundaries (See recent SACC Pionus proposal). Knowing what happens at the contact zone would presumably provide an immediate “answer” to taxon rank in this case, i.e. abrupt turnover with little sign of gene flow or a hybrid swarm. For now, it’s anyone’s guess. The main phenotypic difference is the absence (frontalis) or presence (spodionota) of rufous wingbars.

Here is the rationale presented by García-Moreno et al. (1998):

“Traylor (1985) identified a gap of 150 km between the southernmost frontalis in La Libertad and the northernmost spodionota a little north of the Huallaga Gap in Huánuco, and decided to treat them as a single species until information was obtained about how they interact in a zone of sympatry. This segment of the Cordillera Central remains poorly explored, thus the taxa are recognized currently as subspecies. However, the genetic differences between them (0.059, including 4 tv) is of a level comparable to that of fully recognized species(e.g., S. diadema and S. jelskii: 0.063, O. leucophrys and O. oenanthoides:0.042; Table 1). Although we do not think that species status can be diagnosed solely on the grounds of a quantity of molecular or morphological divergence, we believe that the mtDNA divergence together with biogeographic separation and plumage differentiation suggest that they are different species: S. frontalis (including subspecies albidiadema and orientalis) and S. spodionota (including subspecies boliviana). It should be noted that the Southern taxa (spodionota and boliviana) are phenetically very similar to S. jelskii, whereas the northern S. frontalis albidiadema is characterized by the absence of wingbars and rufous fringes on the tertials (this could be a derived character state; however, a similar lack of wing-pattern also is found within S. spodionota in western Cuzco and Ayacucho).”

Discussion

As far as I can determine, there is no hint that the two groups differ vocally, although this might be because there isn’t much to work with. These birds are usually silent, and their voice is a short trill. Boesman did not attempt and analysis, and there is no hint in Schulenberg et al. (2007) (or anywhere else I’ve looked) of vocal differences. That of course does not mean that critical differences don’t exist – only that we don’t know yet.

My superficial check using xeno-canto provide an N=1 possibility that those differences exist:

The only recording in xeno-canto of the song of spodionota group is a good one of boliviana from Dpto. La Paz by Dane Lane:

https://xeno-canto.org/species/Silvicultrix-spodionota

Note the separated notes at the end of the trill.

In contrast, here is a typical song from the frontalis group from Ecuador:

https://xeno-canto.org/species/Silvicultrix-frontalis

This represents is the way the song is usually rendered phonetically in field guides. Note the lack of separate notes at the end, which only has a slight “hump” in the steady trill.

This has no meaning pending an analysis of a lot more recordings, especially from the central Peruvian population of boliviana’s range and, most critically, from spodionota itself, which would be the type species if we recognized S. spodionota. At this point, for all we know there could be different songs for Peruvian frontalis south of the Marañon, Peruvian boliviana, spodionota, and Bolivian boliviana. Or no consistent variation at all.

Because voice is critical in species limits assessments in the Tyrannidae, I do not think that there is any evidence to change the status quo at this time. The plumage differences are suggestive but not conclusive of anything beyond subspecies rank. The genetic data (a tiny BP sequence of one mitochondrial gene) is inadequate for making taxonomic decisions of any kind. Thus, I strongly recommend a NO on this based on current evidence. I also see no need to rush this because eventually we will likely have conclusive evidence from the uncontacted contact zone. Also note that the difference in presence/absence of wingbars as a species-level character is rendered problematic by the Vilcabamba population of spodionota, which lacks wingbars – see plate above.

Literature Cited: (see SACC Biblio for others):

GARCÍA-MORENO, J., P. ARCTANDER, AND J. FJELDSÅ. 1998. Pre-Pleistocene differentiation amongst chat-tyrants. Condor 100: 629–640 https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=13795&context=condor

TRAYLOR, M. A., JR. 1985. Species limits in Ochthoeca diadema species-group (Tyrannidae). pp. 430-442 in "Neotropical Ornithology" (P. A. Buckley et al., eds.) Ornithological Monographs No. 36.

Van Remsen, June 2025

Note from Remsen on English names: If the taxonomic proposal passes, then we’d need a separate English name proposal. IOC retained “Crowned Chat-Tyrant for the frontalis group even though it’s range is not substantially larger than that of spodionota and used “Kalinowski’s Chat-Tyrant” for the spodionota group.