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 Dan 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.

 

 


 

Vote tracking chart: https://www.museum.lsu.edu/~Remsen/SACCPropChart1044+.htm

 

 

Comments from Niels Krabbe (guest voter): “YES. I see that the sequences used by Garcia-Moreno et al. (1998) have not been uploaded to GenBank, which I find most unscientific. Also, the number of bp compared is low for today's standards.

 

“However, Winger and Bates (2015) gave complete (1041 bp) sequences for the same (ND2) gene for a number of specimens of frontalis (from E Carchi, Imbabura, W Pichincha, and Morona-Santiago, Ecuador, and San Martín, Amazonas, Cajamarca, Huanuco and Apurímac, Peru). I took the trouble to compare these sequences.

 

“The difference between frontalis (from Ecuador and N Peru) and spodionota (from Huánuco, Pasco and Apurímac) is as high as 6%. Furthermore, sequences from spodionota from Huánuco/Pasco (Unchog, Millpo) and Apurímac are virtually identical. Only the Millpo bird differs very slightly (one transition in 1041 bp). Birds from both N and C Ecuador (E Carchi, Imbabura, Cotopaxi, Morona-Santiago) are also virtually identical to each other (Imbabura bird differs by one transition in 1041 bp), whereas they differ from N Peruvian birds by about 1%. N Peruvian birds still differ from C and S Peruvian birds by 6%.

 

“The distinct genetic and morphological difference between frontalis and spodionota lead me to think it safe to rank them as different species.”

 

Winger, B. M. and Bates, J. M. 2015. The tempo of trait divergence in geographic isolation: Avian speciation across the Marañon Valley of Peru. Evolution 69 (3): 772–787.

 

Comments from Andrew Spencer: “I wanted to offer some unsolicited comments on the Silvicultrix frontalis split proposal and add some observations/quick analysis on the vocalizations of the two groups. Hopefully this will add some information for those voting on the issue. None of this is published of course, sample sizes are small, and geographic coverage not the best, but here you go:

 

“Back when I was guiding in the Andes, I noticed while Ecuadorian birds would often respond somewhat nicely to playback when I was trying to show clients the species, those in central and southern Peru were much less cooperative. Digging further after one frustrating experience, I realized all the cuts I was using were from Ecuador, and so I found a recording (I don't remember which at this point) of the southern population to try. Later in the trip I used that recording, with the birds responding much better. This is in spite of the overall vocalization sounding superficially quite similar. I filed this away as "interesting, I'll dig into this later", and then promptly forgot to do anything of the sort.

 

“On a post-guiding career trip to central Peru, I spent some more effort trying to get recordings of chat-tyrants. I eventually managed to find a couple of birds that were actually vocalizing naturally at dawn, seemingly while having a territorial dispute. Unfortunately, they quickly became quiet, and subsequent recordings I obtained were after playback. This did remind me though that I needed to look into vocal differences between the northern and southern groups, which I did at the time, but then again filed away under the "someone should publish on this" excuse.

 

“So, all that said, I do think that at least some of the vocalizations of the northern and southern groups of S. frontalis are consistently and diagnostically different. I primarily looked at what I think of a song in the species. There's always the risk that I'm not comparing entirely analogous vocalizations, or that there is hidden complexity in the repertoire muddying the picture that would become apparent with a larger sample size. But I don't think that's the case here.

 

“To summarize, I think there are two (or three, depending how you separate features out) important and consistent differences in the songs of these taxa that are diagnostic.

 

“Van in his proposal has pointed out one difference: the additional sputtering phrases after the initial longer trill. This is apparently not always present (see the first example in the spec comparison, below), but 3 of 4 samples I found do have it. Tied to this is the less regular frequency pattern over the course of the song. The spodionota group, while generally descending over the length of the song strophe, has a lot of ups and downs. In the frontalis group, the song generally descends much more smoothly, before having the slight "hump" noted by Van near the end of the song.

 

“The other important difference is the overall pitch of the song, especially the intro notes. These are notably higher-pitched in the spodionota group than in the frontalis group. In the spec below, I have red horizontal lines covering the highest and lowest frequencies in the spodionota group, and blue lines doing the same for the frontalis group. Note how the peak of the intro notes for spodionota are around 10.5-11 kHz, whereas those of frontalis are between 7.5-8 kHz. Also note how the majority of the energy in the song strophes averages quite a bit higher for the spodionota group - in most samples almost entirely above the song of the frontalis group.

 

“There are all the usual caveats for these poorly recorded birds, including that it's unknown what happens in the gap between the northernmost recording of the spodionota group in Huánuco and the southernmost of the frontalis group in Amazonas. That said, in my opinion, the combination of plumage differences, molecular data, even if rather dated, and vocalizations all support a split.

 

“Recordings used in the spec comparison, left to right:

 

spodionota group:
ML633678529, Huánuco, Peru
ML470360571, La Paz, Bolivia
ML470352611, Cuzco, Peru
ML143651, Cuzco, Peru

frontalis group:
ML222114391, Pichincha, Ecuador
ML44533211, Imbabura, Ecuador
ML58284, Carchi, Ecuador
ML269800, Caldas, Colombia

 

 

 

Comments from Lane: “NO. This is another case of a very weak study suggesting an interesting taxonomic puzzle without providing enough evidence to clarify what is actually going on. Garcia-Moreno et al. simply didn’t have enough sampling to make much sense of the variation within S. frontalis, and an mtDNA study with 320 bp is very little information. I will vote NO on this simply because the study simply doesn’t offer much to vote on!

 

“My voice comparisons have been strictly with the drawn-out trilled vocalization. This vocalization is what I term the “daytime song” which is not the same as the dawn song that seems to dominate in many Silvicultrix recordings by most other field-workers, and it consists of single “tink” notes. I’ve made efforts to record the daytime songs of Silvicultrix whenever I can and have learned that my comments in Birds of Peru are not accurate (and were written as a result of my ignorance some 20 years ago). With regards to voice, my observations largely agree with what Andrew Spencer has written, although I believe that bolivianus is distinctive within the southern group. See recordings here: https://media.ebird.org/catalog?mediaType=audio&view=grid&taxonCode=crocht1https://media.ebird.org/catalog?mediaType=audio&userId=USER155017&view=grid&taxonCode=crocht1

 

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

 

“Van mentions my cut from La Paz (https://xeno-canto.org/150430,  https://macaulaylibrary.org/asset/638812141, https://macaulaylibrary.org/asset/470360571 all the same cut, but the last is “unconfirmed” within eBird due to being on a historical checklist that was flagged as too long by a reviewer), but I also have recordings of the same song type from Manu Road in Cusco (https://macaulaylibrary.org/asset/470352611) and Cochabamba, Bolivia (https://xeno-canto.org/145014). So. I think it’s safe to say that this song with the repeatedly rising-falling terminal section is characteristic of S. f. boliviana and makes a case for the taxon to be a good one (at least from Cusco south and east into Bolivia). I have few recordings north of Cusco, and there are few others from central Peru aside from Andrew’s and one or two more. These cuts suggest that there is no rising-falling terminal section to the daytime songs of these birds, but birds from Huánuco (https://xeno-canto.org/40518, and Andrew’s cuts noted above) seem to be still higher-pitched and “weaker” than those from Amazonas (https://macaulaylibrary.org/asset/305709521, https://xeno-canto.org/131757 same cut in both) and north of the Marañon (https://xeno-canto.org/704098, https://xeno-canto.org/5905, https://xeno-canto.org/121067). The relative lack of samples makes it difficult to say much about the amount of variation within and among individuals, so I will refrain from doing so. Overall, my impression is that there is much more going on here than just splitting S. frontalis into two, and the Garcia-Moreno et al. paper simply doesn’t address the issue in any meaningful way. Until we have more information, I think it best we wait for additional information (both molecularly and voice) to make an educated decision on what’s going on here. To split based on the current knowledge is a shot in the relative dark and may result in something we’ll have to reverse as more information comes to light.”

 

Comments from Areta: “I vote YES to split spodionota from frontalis. The congruent genetic, plumage, and vocal data support the division. I would of course prefer a proper taxonomic paper dealing with all the details and benefiting from more samples, but the data seem enough to act. The unnamed Vilcabamba population is crying out to be studied and named.”

 

Comments from Robbins: “Given current information I’m on the fence on this one. Given that the plumage of southern O. f. spodionota is more similar to S. jelskii than nominate frontalis, yet Harvey et al (2020) have shown that the latter is more closely related to pulchella, I consider plumage not to be a good indication of relationships in Silvicultrix.

 

“The ND2 data (thanks Niels for bringing in the additional information), are suggestive, but I think most of us would agree that nuclear data are needed for all Silvicultrix.

 

“With regard to vocalizations, more information is needed, especially if perhaps some of these comparisons are not of analogous vocalizations, e.g., dawn song vs. post dawn song.

 

“I think there may well be two species within the currently recognized frontalis, but we need more information. So, for now I vote to wait until those data are available.”

 

Comments from Stiles: “YES to split spodionota from frontalis given recent genetic data, plumages, voice.”