Proposal (947) to South American Classification Committee

 

 

Split Bronze-brown Cowbird (Molothrus armenti) from Bronzed Cowbird (M. aeneus)

 

 

Effect on SACC: The South American subspecies of our current Molothrus aeneus would be treated as a separate species

 

Description of the problem:

The Bronze-brown Cowbird Molothrus [aeneus] armenti has remained little-known until recently, and its status as a subspecies of Bronzed Cowbird Molothrus aeneus rests upon the authority of one scientist, Herbert Friedmann, who, beginning with his review of cowbirds in 1927, considered it a full species, and only in 1963 decided otherwise, seemingly being swayed by his observations of a single captive individual, but without providing a rationale.

 

Molothrus [a.] armenti Cabanis, 1851 (based on Lichtenstein’s 1826 label name) was long known from only four specimens from Cartagena and “Savanilla”, Colombia (=Sabanilla, near Baranquilla), though Friedmann (1957) considered two further specimens (from Demerara, Guyana and Venezuela) to be doubtfully identified, correctly it would appear as no further reports have come from these countries. Two of the Cartagena specimens were lost and no further specimens or living individuals were found for over a hundred years, despite special effort by e.g., Dugand (1947) and Carriker (in Friedmann 1957), and the exact collection localities were uncertain. When a live adult male turned up in a shipment of cagebirds from Leticia, Amazonian Colombia, it was initially heralded as a rediscovery (Friedmann 1957), and Leticia was accepted as a genuine locality by Meyer de Schauensee (1964, 1966, 1970), who then considered the specimens from Cartagena of doubtful provenance. Subsequently, however, it became evident that the Leticia origin of the shipment was instead highly doubtful because the many collectors operating there never obtained any cowbirds, and the likelihood is that the birds were brought on board during refueling in Barranquilla, where a Leticia-based bird dealer had another operation (Camacho & Rodríguez-Mahecha 1986).

 

Although usually treated as a full species (e.g., Friedmann 1927, 1933, Hellmayr 1937, Meyer de Schauensee 1966, 1970, Camacho & Rodríguez-Mahecha 1986, Hilty & Brown 1986, Sibley & Monroe 1993, Rada Quintero 2002, Gill & Wright 2006, Fraga 2011, del Hoyo & Collar 2016, BirdLife International 2020, Hilty 2021), some of these authors expressed doubt as to its species status, and it was considered a subspecies by others (e.g., Meyer de Schauensee 1964, Parkes & Blake 1965, Blake 1968). Then, after its 1969 rediscovery in the wild at P.N. Isla de Salamanca by Gilberto Toro-García, Dugand & Eisenmann (1983; as interpreted by Friedmann, who at least finished, or perhaps wrote the paper because both authors of record were by then deceased) examined a series from the rediscovery site and deemed that it “cannot be looked upon as other than a southernmost race of … M. aeneus.” Dugand & Eisenmann (1983) then went on to reiterate some of the known characters by which armenti differs from aeneus, but their posthumously published opinion as to its subspecific status has been widely followed (Ridgely & Tudor 1989, AOU 1983, 1998, Dickinson 2003, Dickinson & Christidis 2014, McMullan & Donegan 2014, McMullan et al. 2018, Avendaño et al. 2017, Ayerbe-Quiñones 2019, Clements et al. 2019, Remsen et al. 2020). By 1963, Friedmann (1963) was treating armenti as a subspecies of aeneus, although without any comment as to why and without benefit of the larger series later available. The less extravagant plumage and structural features of armenti compared to aeneus were in fact used as evidence by Parkes & Blake (1965) to sink the genus Tangavius into Molothrus, with the argument that armenti bridged the gap between Bronzed and typical cowbirds. Nevertheless, later in the same paper they stated ‘Although its differences in color and proportions suggest that it might be specifically distinct, armenti is now considered by Dr. Friedmann to be conspecific with aeneus. We propose to follow his recommendation, based in part on observations of a living adult male armenti in the National Zoo…’ (Parkes & Blake 1965). Presumably these observations of the living bird were Friedmann’s, and it seems unlikely that Bronzed Cowbirds were also present simultaneously in the zoo for direct comparison. Subsequently, however, this treatment was followed by others, including the AOS classification committees. Dugand & Eisenmann (1983), who did examine the larger series unavailable at the time Friedmann decided on subspecific status, but it is not clear whether the statement about its being a race of aeneus was theirs or the subsequent opinion of Friedmann, who finished the manuscript for the predeceased Dugand and Eisenmann after having been sent their notes and correspondence by F. Vuilleumier (Friedmann’s footnote in Dugand & Eisenmann 1983). In any case, it does not appear that convincing argumentation for the conspecificity of armenti with aeneus has been published.

 

No DNA-based phylogenetic studies appear to have thus far included armenti. Nevertheless, though it seems clear that armenti is closely related to aeneus, it is quite morphologically divergent from Bronzed Cowbird, as noted in various sources (especially Jaramillo & Burke 1999):

 

·      Much smaller size (the smallest cowbird). For males (n=8), wing vs. the three races of aeneus averaged 96.5 vs. 116.5, 119.0, 108.7; culmen 16.7 vs. 23.0, 23.0, 21.3; tail 61.4 vs. 79.6, 85.0, 73.0; for females (n=8), wing 87.9 vs. 108.7, 104.5, 102.6; culmen 16.2 vs. 20.6, 19.8, 19.1; tail 59.4 vs. 73.0, 73.5, 73.5; measurements from Jaramillo & Burke 1999);

·      relatively smaller bill (see Friedmann’s 1933 Fig. 6) and feet; see above measurements;

·      greatly reduced sexual size dimorphism;

·      redder iris in adult female;

·      head and body of adults of both sexes glossy brown, much like head color of male Brown-headed Cowbird;

·      neck ruff present in males but much reduced;

·      outer primary not emarginate, unlike Bronzed Cowbird;

·      much reduced hairlike texture of breast feathers in males.

 

New information: 

We have not had the opportunity of independently studying specimens of armenti. However, several photos of armenti are now available online on eBird, and these show that iris color of males is not consistently different from Bronzed Cowbird, although perhaps not as brilliant red, and irides of female armenti can be nearly as red as in males (brownish to pale orange in female aeneus).

 

Thirteen recordings of armenti are available as of 26 August 2022 on xeno-canto (https://www.xeno-canto.org/species/Molothrus-armenti?view=3), and although somewhat variable and similar in quality to the plentiful material there and on Macaulay Library of North to Middle American M. aeneus, none share the same pattern. Its vocal distinctiveness has already been noted by Fraga (2011) and del Hoyo & Collar (2016), and it seems to be relatively quiet.

 

For years after its rediscovery, armenti was mainly reported from P.N. Isla de Salamanca (e.g., Gochfeld et al. 1980), but remained relatively little-known, and from few localities (Ridgely & Tudor 1989). However, with the growth of birding in Colombia that has changed, as can be seen from the eBird map (https://ebird.org/species/brocow; Panama records are aeneus), and further data and records have been enumerated in Arzuza Buelvas et al. (2017), and thus although now much better known, major areas of its life history are still mysterious such as its host species (Arzuza Buelvas et al. 2017). Donegan et al. (2016) stated that “Bronze-brown Cowbird Molothrus armenti is not seen east of Salamanca”, but Freeman et al. (2011) and others have recorded it east to SFF Los Flamencos. It has also been reported to the west in Córdoba Department (Estela & López-Victoria 2005). Given its range restriction and evidently small population size, the species was considered Threatened (Rada Quintero 2002) or even endangered (Fraga 2011), but has now been downgraded to Vulnerable (Renjifo et al. 2016). However, it does occur in degraded and pastoral areas and over a broader area than earlier believed. Because the range of the Bronzed Cowbird is expanding in Panama with deforestation, it seems only a matter of time before secondary contact is established between aeneus and armenti.

 

One putative ecological difference mentioned by several authors, the seeming lack of affinity of armenti for cattle (e.g., Hilty & Brown 1986, Jaramillo 1999), does not appear to hold. A known site for this species is a cattle pen along the highway near Salamanca, where D. Donsker’s guide took him to see six individuals of armenti along with other blackbirds on 15 Mar 2012. It has even been reported in a park in downtown Magdalena (“red eye seen clearly”; https://ebird.org/checklist/S30013686), and may feed among domestic fowl (https://ebird.org/checklist/S53399078; Fraga 2011).

 

Most recent treatments other than HBW/BirdLife and Gill & Wright (2006) and those following these lists continue to treat armenti as a subspecies of aeneus, including in-country sources (e.g., McMullan & Donegan 2014, McMullan et al. 2018 [not seen], Donegan et al. 2015, Ayerbe-Quiñones 2019). This is likely to be largely due to historical inertia. We consider that there is a strong case for the treatment of armenti as specifically distinct, given its morphological and vocal differentiation, that a strong case for conspecificity was never made, and that continued subspecific status would need to be based upon evidence of which we are unaware.

 

English name.—The name “Bronzed Cowbird” is vastly more familiar and entrenched for the widespread North and Middle American M. aeneus, which was also long known as Red-eyed Cowbird (Friedmann 1957). The name Bronze-brown Cowbird is the most-used name for armenti (and continues to be used in the most recent field guide to Colombia, Hilty 2021), but it has also been known as Arment’s Cowbird (in e.g. Hellmayr 1937), Cabanis’s Cowbird (Brabourne and Chubb 1914), and Colombian Red-eyed Cowbird (Friedmann 1957). Although Friedmann (1957) quoted E. Stresemann as having informed him that armenti stems from the Latin word for armentum, meaning a drove of cattle, Jobling (2010) indicates it was named after T. Arment, a “collector in Colombia”.

 

Recommendation:

 

We recommend that M. armenti be considered specifically distinct, for the reasons stated above, and we recommend that it continue to be known as Bronze-brown Cowbird, which is highly entrenched. If voting yes for the split (part A), please also vote for an English name (part B).

 

Literature cited:

 

American Ornithologists’ Union (1983). Check-list of North American birds. Sixth Edition. American Ornithologists’ Union, Lawrence, KS.

American Ornithologists’ Union (1998). Check-list of North American birds. Seventh Edition. American Ornithologists’ Union, Lawrence, KS.

Arzuza Buelvas, D., C. Olaciregui, J. Reyes, & H. F. Rivera-Gutiérrez (2017). In: Renjifo, L. M., A. M. Amaya-Villarreal, J. Burbano-Girón, & J. Velásquez-Tibata (Eds) (2017). Libro Rojo de Aves de Colombia. Volumen II. Pontificia Universidad Javeriana, Instituto de Investigación de Recursos Biológicos Alexander von Humboldt. Downloaded from http://www.humboldt.org.co/es/component/k2/item/1191-libro-rojo-aves-colombia-2 on 26 June 2022.

Avendaño, J. E., C. I. Bohórquez, L. Rosselli, D. Arzuzu-Buelvas, F. Estela, A. M. Cuervo, F. G. Stiles, & L. M. Renjifo (2017). Lista de chequeo de las aves de Colombia: una síntesis del estado de conocimiento desde Hilty & Brown (1986). Ornitología Colombiana 16: eA01.

Ayerbe-Quiñones, F. (2019). Guía ilustrada de la avifauna colombiana. Second ed. Wildlife Conservation Society / Colombia Program, Colombia. BirdLife International. 2020. Species factsheet: Molothrus armenti. Downloaded from http://www.birdlife.org on 09/08/2020.

Blake, E. R. (1968). Family Icteridae, American Orioles and Blackbirds. In Paynter Jr., R. A. (ed.) Check-list of birds of the World. Volume 14. Harvard University Press, Cambridge, Massachusetts.

Brabourne, Lord, & C. Chubb (1914). The birds of South America. Volume 1. R. H. Porter, London.

Camacho, J. I. H., & J. V. Rodríguez-Mahecha (1986). Status geografico y taxonomico de Molothrus armenti Cabanis 1851 (Aves: Icteridae). Caldasia 15 (71/75): 655–664.

Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, & C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/ 

del Hoyo, J., & N. J. Collar (2016). HBW and BirdLife International illustrated checklist of the birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.

Dickinson, E. (ed.) (2003). The Howard & Moore complete checklist of the birds of the world. 3rd Edition. Christopher Helm, London.

Dickinson, E. C., & L. Christidis (eds.) (2014). The Howard and Moore complete checklist of the birds of the world. 4th edition. Volume Two. Passerines. Aves Press Ltd., Eastbourne, UK.

Donegan, T., J. C. Verhelst, P. Salaman, O. Cortés, D. Caro, & A. Quevedo (2015).  Listado de Aves de Colombia. Version 4.0 (17 April 2015). www.proaves.org.

Donegan, T., J. C. Verhelst, T. Ellery, O. Cortés-Herrera, & P. Salaman (2016). Revision of the status of bird species occurring or reported in Colombia 2016 and assessment of BirdLife International’s new parrot taxonomy. Conservación Colombiana No. 24: 12–36.

Dugand, A. (1947). Aves del Departamento del Atlántico, Colombia. Caldasia 4: 499–648.

Dugand, A., & E. Eisenmann (1983). Rediscovery of, and new data on, Molothrus armenti Cabanis. Auk 100: 991–992.

Ellison, K., & P. E. Lowther (2020, last updated 2009). Bronzed Cowbird (Molothrus aeneus), version 1.0. In: Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.brocow.01

Estela, F. A., & M. López-Victoria (2005). Aves de la parte baja del río Sinú, Caribe colombiano; inventario y ampliaciones de distribución. Boletin de Investigaciones Marinas y Costeras 34: 7–42.

Fraga, R. (2011). Family Icteridae. (New World Blackbirds.) In: del Hoyo, J., Elliot, A. & Christie, D. A. (eds.) Handbook of the birds of the world. Volume 16. Tanagers to New World Blackbirds. Lynx Edicions, Barcelona.

Freeman, B. G., S. L. Hilty, D. Calderón-F., T. Ellery, & L. E. Urueña (2011). New and noteworthy bird records from central and northern Colombia. Cotinga 34: OL 5-16.

Friedmann, H. (1927). A revision of the classification of the cowbirds. Auk 44: 495–508.

Friedmann, H. (1933). Notes on Arment’s Cowbird, Tangavius armenti (Cabanis). Ibis 16: 492–494.

Friedmann, H. (1957). The rediscovery of Tangavius armenti (Cabanis). Auk 74: 497–498.

Friedmann, H. (1963). Host relations of the parasitic cowbirds. United States National Museum Bulletin No. 233. Smithsonian Institution, Washington, D. C.

Gill, F. B., & M. Wright (2006). Birds of the world: Recommended English names. Princeton University Press, Princeton, NJ.

Gochfeld, M., S. Keith, & P. Donohue (1980). Records of rare or previously unrecorded birds from Colombia. Bulletin of the British Ornithologists’ Club 100: 196–201.

Hellmayr, C. E. (1937). Catalogue of birds of the Americas and adjacent islands. Part 10. Icteridae. Field Museum of Natural History, Chicago.

Hilty, S. L., & W. L. Brown (1986). A guide to the birds of Colombia. Princeton University Press, Princeton, NJ.

Hilty, S. L. (2021). Birds of Colombia. Lynx and BirdLife International Field Guides. Lynx Edicions, Barcelona.

Jaramillo, A., & P. Burke (1999). New World blackbirds. The icterids. Princeton University Press, Princeton, NJ.

Jobling, J. A. (2010). The Helm Dictionary of Scientific Bird Names. Christopher Helm, London.

McMullan, M., & T. Donegan (2014). Field guide to the birds of Colombia. ProAves, Bogotá.

McMullan, M., T. M. Donegan, G. Pantoja-Peña, T. Tuncer-Navarro, A. Bartels, & T. Ellery (2018). Field Guide to the Birds of Colombia. Rey Naranajo Editores, Bogotá.

Meyer de Schauensee, R. (1964). The birds of Colombia. Livingston, Narberth, PA.

Meyer de Schauensee, R. (1966). The species of birds of South America with their distribution. Livingston, Narberth, PA.

Meyer de Schauensee, R. (1970). A guide to the birds of South America. Livingston, Narberth, PA.

Parkes, K. C., & E. R. Blake (1965). Taxonomy and nomenclature of the Bronzed Cowbird. Fieldiana, Zoology 44(22): 207–216.

Rada Quintero, E. (2002). Molothrus armenti. Pp. 453–457 in: Renjifo, L. M, A. M. Franco, J. D. Amaya, G. H. Catan, & B. Lopez (eds.) Libro rojo de aves de Colombia. Serie Libros rojos de especies amenazadas. Instituto de Investigación de Recursos Biológicos Alexander von Humboldt y Ministerio del Medio Ambiente. Bogotá, Colombia. Downloaded from http://repository.humboldt.org.co/handle/20.500.11761/31407 on 26 June 2022.

Remsen, J. V., Jr., J. I. Areta, C. D. Cadena, S. Claramunt, A. Jaramillo, J. F. Pacheco, J. Perez Emán, M. B. Robbins, F. G. Stiles, D. F. Stotz, & K. J. Zimmer (Version 11 February 2020). A classification of the bird species of South America. American Ornithological Society. http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm

Renjifo, L. M., A. M. Amaya-Villarreal, J. Burbano-Girón, & J. Velásquez-Tibata (eds.) (2017). Libro Rojo de Aves de Colombia. Volumen II. Pontificia Universidad Javeriana, Instituto de Investigación de Recursos Biológicos Alexander von Humboldt. Downloaded from http://www.humboldt.org.co/es/component/k2/item/1191-libro-rojo-aves-colombia-2 on 26 June 2022.

Ridgely, R. S., & G. Tudor (1989). The birds of South America. Volume 1. The Oscine Passerines. University of Texas Press, Austin, TX.

Sibley, C. G., & B. L. Monroe, Jr. (1993). A world checklist of birds. Yale University Press, New Haven, CT.

 

 

Pamela C. Rasmussen and David B. Donsker, June 2022

 

 

Note from Remsen: This is from a manuscript that is in review; normally, we would just wait for it to appear, but the IOC’s Working Group in Avian Classification (on with Nacho is our representative) could use our input ASAP.

         Also, for voting, for those of you who vote yes who also vote on English name issues, I am going to assume that use of the historical name Bronze-brown Cowbird is acceptable unless you state otherwise.  I don’t see any point in doing a separate subproposal on this unless someone objects.

 

_______________________________________________________________________________

 

Comments from Stiles: [YES]. I have a small set of data for this species, but some interesting points can be made. For one thing, by weight armenti is less than half as heavy as aeneus, sex for sex. Mean weights: for males, armenti: 34.65 g, n=2; aeneus: 67.76 g, n=6 (from Costa Rica; for females, armenti: 24.60 g; aeneus: 55.12 g (n=5, again from Costa Rica). Sexual dimorphism in weights is thus actually greater for armenti than for aeneus, the opposite from plumage differences, which are less for armenti. My field experience with armenti is limited, but in both my contacts with this bird near Cartagena, my impression of its voice was that it differed considerably from what I had often heard from aeneus in Costa Rica, although I was unable to obtain recordings.  Another observation: in both of my observations of small flocks of armenti. I noted an unusual plumage, presumably of young males, in which the heads and breasts were blackish, concolor with the upperparts, but sharply separated from the slightly paler brown of the abdomen (similar to one of the females in the ICN collection), giving a “hooded” aspect; I had never seen such a plumage in years with aeneus in Costa Rica. Unfortunately, this plumage is not represented in the small series in ICN. In sum, I think that these observations further tip the balance for species status of armenti, so YES to this proposal.”

 

Comments from Claramunt: “NO. I really don’t see the evidence. I only see anecdotal information that is difficult to interpret.”

 

Comments from Remsen: “YES.  Santiago is correct in that the evidence is a collection of anecdotes.  Obviously, a formal, quantitative study would be needed if this were a novel split, especially on male displays, which would obviously be critical to assessing potential gene flow in this promiscuous species.  But in cases like these, I think we should also evaluate the rationale for their treatment as conspecific as well, which in this case rests on the following (from Dugand and Eisenmann):

 

“With 12 specimens now available for study in the museums of New York and Bogota, it becomes clear that armenti cannot be looked upon as other than a southernmost race of the species M. aeneus. M. armenti agrees with aeneus in the emargination of the primaries in the adults. Inasmuch as no adult females of armenti have been described until now, it may be put on record that in coloration they resemble, but are not quite as glossy as, female M. aeneus assimilis. The adult males of armenti resemble those of aeneus but are less bronzy, more brownish. The brown color of the head and body of armenti, while more iridescent, is not unlike that of the head of male ater (Parkes and Blake 1965). The bill of adult armenti is somewhat shorter and slenderer than that of aeneus.”

 

“Personally, I don’t see this as compelling logic for taxon rank either way.  Note that when Dugand and Eisenmann (or was it Friedmann? See proposal) wrote their paper, armenti was barely known, and a main theme of the paper was where armenti actually occurred, because an imported zoo bird was thought to have come from Leticia on the Amazon.  The other main point of the paper is that the species was previously known from just two extant specimens, and Dugand and Eisenmann now had ca. 10 new specimens collected by Gilberto Toro-Garcia, a Colombian who was in-charge of the newly created Parque Nacional de la Isla de Salamanca.  (That Toro-Garcia was not included as a co-author on this paper is unfortunate but reflects different attitudes on authorship of that era.)”

 

“So, what we have here is competing interpretations of anecdotes.  In my opinion, those assembled by Rasmussen and Donsker place burden-of-proof on treating armenti as just a subspecies, especially since some of them might be relevant to mate selection.

 

“The only thing I might add it that using a comparative approach, my superficial assessment of subspecies differences in the other two widespread polytypic Molothrus, ater and bonariensis, is that they are minor compared to those between armenti and aeneus.  In M. ater, the three subspecies are defined based on size and female plumage; male plumages are evidently indistinguishable.  In M. bonariensis, subspecies are also defined primarily on female plumage and size.  Variation among the other three subspecies of aeneus is largely in female plumage and size (Jaramillo & Burke).  With all appropriate caveats concerning these comparisons, armenti would seem to be an outlier in terms of Molothrus subspecies-level differentiation.”

 

Comments from Areta: “YES. A borderline case. In the face of uncertainty and the lack of consensus on how to treat armenti, the accumulation of structural, size, plumage, and vocal differences occurring over a short geographic distance and across an avifaunal break tips the scale towards species recognition for armenti. This is a judgment call, and the case begs for an integrative study.”

 

Additional comments from Stiles: “Ridgway also gaves the same set of measurements for M. aeneus, so I made the corresponding bill measurements for armenti. (note that the appropriate comparison is with the nominate and largest race of aeneus (called robustus in Ridgway); the two smaller races are resident in extreme SW US to Jalisco, and Guerrero-Oaxaca in Mexico and are thus not likely to approach Colombia, whereas M. a. aeneus is known southeast to central-western Panama and is expanding its range eastward. An interesting feature of both M. a. aeneus and armenti is that the bills of the females average larger than those of the males and, comparing the sexes, show differences in shape. The sexual dimorphism in the CtB/ BHb ratios is: for aeneus = 0.992; for armenti = 0.968 – bills of armenti average more different from those of males (being relatively longer and slenderer). Another difference: Ridgway´s diagram of the wing of male aeneus clearly shows that the three outermost primaries have the inner webs distinctly deeply notched; in male armenti, none of these primaries are notched. Thus, the sound of the courtship flight of aeneus will be distinctly different from that of armenti (another difference in favor of species status for armenti).

 

Comments from Lane: “NO. I remain rather unimpressed by the plumage and voice of M. armenti as being sufficiently distinct from M. aeneus as to suggest different species. The differences in size may be enough to move me, but I'd like to see a far more explicit comparison (molecularly, vocally, behaviorally, morphologically) of the two groups of taxa to feel that they merit species status. I will point out that the "13" cuts of M. armenti in X-c are fraught with duplicates and even one or two triplicates, so there are more like 6 cuts, from only two days and two localities, so perhaps only representing two individuals... and my experience from M. aeneus is that a single individual can give several different song types and fragments of songs, so any perceived differences based on the cuts on X-c are, to me, fairly meaningless. A far larger sample would be necessary for me to sit up and take notice. Indeed, I hear vocalizations I would not be able to separate from common vocalizations I regularly hear from M. aeneus here in Louisiana and Texas. Furthermore, the "hooded" plumage Gary mentioned in his comments is one I have seen among M. aeneus in the USA (e.g.: https://macaulaylibrary.org/asset/251320751, https://macaulaylibrary.org/asset/56040011, https://macaulaylibrary.org/asset/102409151, https://macaulaylibrary.org/asset/442149081), and is presumably a stage in the aging process and so should not be seen as a distinctive plumage class that would merit difference between the two groups.”

 

Comments from Robbins: “NO.  I had looked at the Molothrus proposal a month or so ago and came away with the same impression as Dan.  As a result, I decided not to vote on the proposal at that time.  As Dan noted, the sample size for the vocalizations and photos is quite small, i.e., people on a tour had photos taken by one person put on all the eBird checklists.  I didn't appreciate what Dan stated concerning the "hooded" plumage appearing among other aeneus populations.  Finally, there is considerable variation in morphometrics among the aeneus taxa, so if armenti is indeed smaller, that may be meaningless for ascertaining species status.  Given these issues, I vote NO for recognizing armenti until we have more information.

 

Comments from Bonaccorso: “NO. I would love to say yes, because of the conservation concerns. However, the problem is that size differences could result from local adaptation, and plumage differences seem to be subtle (“lacking the bronzy cast of other subspecies” (Ellison and Lowther 2020)). Also, since cowbird songs are so variable, a rich comparison would be needed to identify homologous vocalizations. On top of that, there are no DNA data. So, we are deciding based on very little data.”

 

Comments from Zimmer: “A very tepid YES.  I don’t have strong feelings about this one way or the other, and agree with Dan and Mark that much of the evidence for splitting is shaky.  However, what I come back to, is that the evidence for the original lump was even shakier.  The status quo becomes harder to defend, when we consider that it became the entrenched position only through the unjustified overturning of the prior status quo.  The anecdotal accounts of vocal differences and the limited biometric and plumage data, imperfect as they may be, are enough to tip the scales toward the original status quo in my mind, and by doing so, may generate enough interest for someone to get out there and really nail this thing down, one way or the other.”

 

Comments from Pacheco: “NO. I have read the arguments for and against the split and agree that the best decision requires waiting for DNA data.”

 

Additional comments from Stiles: “First, the evidence for conspecificity with M. aeneus, based principally on Friedmann, who in turn used the unpublished information from Dugand & Eisenmann posthumously. Friedmann stated that there was no difference in the degree of emargination between aeneus and armenti; however, this is incorrect (see above). Second, the size difference is dismissed by Dan as a useful criterion. However, if one uses as a yardstick the differences among the three subspecies of aeneus, these are far less than that between these and armenti, especially given the different degrees of sexual dimorphism between armenti and nominate aeneus. Also, I have looked at the 4 photos of supposedly hooded aeneus given by Dan; only one approaches the hooded plumage of armenti that I described and in even that one, the match is by no means perfect (head to upper breast black, breast a brighter brown that shades into black on the abdomen, vs. a  black head to breast, more sharply set off from a dark brown abdomen). So in sum, the evidence for conspecifity is definitely not wholly satisfactory.”