Proposal (561) to South American Classification Committee

Transfer Milvago chimango to Phalcoboenus

Effect on SACC list: If this proposal passes, Milvago chimango would become Phalcoboenus chimango

Background: Milvago chimango traditionally has been treated in Milvago, and I am unaware of any doubts concerning its placement there. In fact, Brown & Amadon (1968) treated them as forming a superspecies, but this is clearly an error because they overlap fairly extensively in their distribution (in Paraguay, Uruguay, extreme S Brazil). Vuilleumier (1970) questioned their close relationship because of differences in shape and ecology, but he retained chimango in Milvago.

New information: Fuchs et al. (2012) sampled all of the caracaras using DNA sequence data from mtDNA (2308 bp) an nDNA (5008 bp). Milvago chimango was not the sister taxon to M. chimachima in either the mtDNA or nDNA analyses, but was the sister to Phalcoboenus with weak or no support. However, in the concatenated dataset, support for that relationship was much stronger. In all analyses, Daptrius ater was sister to M. chimachima. Clearly, Milvago as traditionally defined is not monophyletic. Here is their species tree:

Fuchs et al. (2012) considered 4 taxonomic options:

1. One genus: Merge all species from Milvago and Phalcoboenus into Daptrius (which has priority).

2. Two genera: Move Milvago chimachima into Daptrius and Milvago chimango into Phalcoboenus.

3. Three genera: Move chimango into Phalcoboenus.

4. Four genera: Retain traditional generic boundaries and describe a new genus for chimango.

They recommended Option 3 (= 3 genera; Milvago chimango becomes Phalcoboenus chimango) because “it maintains monophyletic genera while recognizing differences in overall shape, diet and habitat use between and M. chimachima and D. ater.”

Recommendation: I have no recommendation on this one, and have written the proposal to follow the recommendation of Fuchs et al. Their option 4 is clearly out in the absence of a genus for chimango, but otherwise I have no opinion on the other three. Although I once knew D. ater and M. chimachima very well, I don’t know the rest well enough to contribute to the subjective evaluation, and will listen to what others have to say. Strictly on plumage and general shape, Daptrius and Phalcoboenus are fairly similar, and Daptrius ater is certainly more similar to them in general behavior and ecology than it is to its former congener (now Ibycter americanus) and obviously more similar in plumage to Phalcoboenus than it is to Milvago chimachima (thus I would rank Option 2 fairly unpalatable). So, pending input from more knowledgeable people, I think Option 1 (Milvago and Phalcoboenus into Daptrius) is viable – these are all generalists of open country with roughly similar size, proportions, and behavior.

A YES vote would endorse the solution proposed by Fuchs et al. (2012), Option 3 above, and a NO would indicate favoring another option (presumably #1?).

Literature Cited

BROWN, L. AND D. AMADON. 1968. Eagles, hawks, and falcons of the world. 2 Vols. Country Life Books, Hamlyn, Middlesex, U.K.

FUCHS, J., J. A. JOHNSON, AND D. P. MINDELL. 2012. Molecular systematics of the caracaras and allies (Falconidae: Polyborinae) inferred from mitochondrial and nuclear sequence data. Ibis 154: 520-532.

VUILLEUMIER, F. 1970. Generic relations and speciation patterns in the caracaras (Aves: Falconidae). Breviora 355: 1-29.

Van Remsen, October 2012

Comments from Zimmer: “NO. Like Van, I don’t feel that I know the species in Phalcoboenus well enough to properly inform my opinion on this one. However, I do know the other species (Daptrius ater, Milvago chimachima & M. chimango) well, so here goes…Based on the molecular data, we clearly need to do something with chimango. Looking at morphology (particularly plumage patterns), vocalizations, and ecology, it doesn’t make much sense to me to shift chimango to Phalcoboenus, while retaining Daptrius (most similar in plumage to Phalcoboenus, but sister to chimachima) and Milvago (for chimachima). Therefore, I would say NO to the proposed Option #3, and YES for Option #1 (merging all species from Milvago and Phalcoboenus into Daptrius, which has priority), which would still be consistent with the molecular data.

Comments solicited from Nacho Areta: “This is a tough one to decide upon. I lean toward the single genus treatment: as you said, they are all fairly open-area generalists and they all share their slim wings (with a noticeable 'primary break') and long, slender tails, giving them a very similar shape. Biogeographically, the only coherent group appears to be Phalcoboenus sensu stricto, whose species seem to be less vocal than Ibycter, Daptrius, or the Milvagos and are restricted to cold Andean-Patagonian open habitats. I don't think that any of the 'intermediate' options is reasonable, and I think that either a five genera or a single genus option are the most palatable choices here. The oddballs are the Milvagos (if they were not here, I suspect everybody would be happy to have a single genus for the black-and-white and painted-face members). Merging chimango into Phalcoboenus without merging chimachima into Daptrius seems like the worst possible option, as there are more (or as many) differences in plumage and vocalizations between chimango-Phalcoboenus than between chimachima-Daptrius. If separate genera are kept for chimango and chimachima, then the same should be done for Ibycter, Daptrius, and Phalcoboenus. If pushed hard, I would argue that merging them in a single genus would be more informative than over-splitting this small group of birds into five different genera. Looking at Falco, the merger becomes easier to digest. Yet perhaps the best thing to do is to wait for a more solid phylogeny with well-supported branches?

Comments from Pearman: “I agree that Phalcoboenus is the most coherent group and this is a crucial point in relation to the taxonomy. The four Phalcoboenus are robust, have three distinct age-related plumages (the juveniles strongly resemble one another including australis), adults always exhibit a white terminal band to (contra Nacho) a fairly broad tail (unlike chimachima/chimango), which is often fanned somewhat in flight, have a wing shape that is closest to Caracara but with round-tipped primaries (unlike other caracaras), and their raucous grating calls are very different from all the other genera/species mentioned, and they are also less vocal in general terms. None of these features tally with chimango, or chimachima or Daptrius making options 2 and 3 untenable. Daptrius and narrow-tailed Milvago chimachima and chimango all produce different kinds of screaming vocalizations. It is also noteworthy that chimachima is the only species showing three very distinct age-related plumages, unlike chimango and Daptrius. My personal view is that we have three species which just don’t sit well with Phalcoboenus and that there is too much information that would be forfeited with a rather radical merger of all genera into Daptrius (option 1) which, by itself, is an oddball caracara. Therefore, I believe that the erection of a new genus for chimango (option 4) is a better solution.

I’m not saying that I am going to write up a new genus, but I think this is a better course of action than lumping into Daptrius, which is kind of an easy way to sweep this problem under the carpet.”

Comments from Nores: “NO. First, I do not understand why all the species are considered open-area generalists, when Daptrius and Ibycter are, at least in Amazonia, forest birds? I have watched the two species on many occasions and always in forests. Second, Milvago chimango and M. chimachima have very similar behavior and the young of M. chimachima are virtually the same as adults of M. chimango. I have seen more than one experienced ornithologists confuse the young of M. chimachima with M. chimango. When I first saw M. chimachima young in Brazil more than 30 years ago, I thought how odd that M. chimango reaches so far north. Anyway, if we consider mainly the molecular analysis, then we can almost forget about the morphological. Fuchs’ tree, in this respect, is one of the most illogical I've ever seen. I remember a sentence by Robbins: ‘I was particularly surprised with the molecular data and I quickly realized that morphology and vocalizations (except for mostly sister relationships) often lead to wrong conclusions about relationships’. I vote option 1.

Comments from Robbins: “NO. Once again, a subjective decision on how to deal with a monophyletic clade. Why not put all in one genus, Daptrius.”

Comments from Stotz: “NO. I favor option 1, all in Daptrius.”

Comments from Sergio H. Seipke: ”I was prompted by Nacho Areta to submit for your consideration my views on this subject.  As I read previous comments made by others here, I found some inconsistencies with my own observations.  Most of what follows is the result of my own work in the field and in museums, it has not been published elsewhere, and it will be included in a book I am preparing (Seipke, S. H.  Raptors of South America. Princeton University Press.)  I wandered beyond the point in question here (Transfer Milvago chimango into Daptrius) as I deemed it necessary.  I used specific epithets standing alone to refer to individual species (instead of using customary generic names) as to avoid confusion or ambivalences.  Eventually, I chose not to be too formal at times, as it is more fun.

“Americanus is truly way out there on its own in most respects among the Neotropical caracaras.  Adults and juveniles look virtually the same.  They are extremely vocal (and loud!).  They are, for the most part, food specialists (wasps, bees, hornets) and show very specialized feeding behavior (they fly by insects nests hitting them until they fall and feed only when adult occupants have left).  They have red feet. Their tails are obviously graduated.  Their flight profile (and behavior) is more akin to guans or chachalacas than to any caracara.  They are true forest birds, as they occur in primary forests even far away from bodies of water or edges (although they would wander to edges where deforestation advances rapidly or small openings in continuous forest).  Placing americanus into anything other than its own genus will mask this significant differentiation.  

“Carunculatus, megalopterus, albogularis and australis share several plumage traits (developmental sequence) not present in the rest of the species in the clade considered (Polyborinae sensu Fuchs et al. 2012, a rather unfortunate name if I may say so, as Polyborus is a synonym of Circus!).  Namely, they all have four immature basic plumages plus a definitive basic plumage.  The first two immature basic plumages are very similar (overall brown), and the reason why they have only been described so far only for australis.  The progression of character states from basic I to basic IV is very similar for all four species (to the point that all three truly continental forms can be readily told apart only after well into the third year of age).  In all four species, these two 'cryptic' juvenile plumages can be told apart by the shape of the primaries (pointed in the first basic, rounded in the second basic), the coloration of the bill, facial skin, and legs, and other minor differences.  All four species are broad-tailed.  These species can and do soar on thermals without flapping (unheard of in other caracaras, except rarely in chimango).  All four species are ground dwellers and take carrion, insects, and other animals they can catch on foot.

“Chimango also has only two age plumages (juvenile and adult), and both are quite similar.  But unlike any other caracara (that I am aware of) chimango shows sexual dimorphism in the coloration of bare parts of adults of different sexes.  

“Although ater, chimachima, and chimango (the 'screaming-caracaras') share overall proportions (all three being rather slim and narrow-tailed), the first two are longer-tailed, shorter-winged birds (very obvious on perched individuals) that fly on rather stable, linear trajectories, even when flapping, whereas chimango, on the other hand, is very erratic on the wing, even when gliding.

“Both chimango and chimachima are rather catholic in their habitat use, the former having populations very partial to (temperate) forests, the later occurring in open grasslands and primary forest along major rivers too (e. g., sand banks).  On the other hand, ater is rather partial to major rivers in primary forest (where it is syntopic with chimachima).  Bottom line being, habitat is of limited use here.

“In view of all-of-the above I think that the most informative treatment of the 'Polyborinae', one that would not necessarily conflict with Fuchs et al. 2012, would be to place ater and chimachima together in Daptrius and leave everything else the same.  

“Placing chimango into Phalcoboenus would—well—destroy our notion of what a Phalcoboenus is.   Merging all into Daptrius is, from my perspective, quite unnecessary, and artificially homogenizing.  If you can have Ibycter americanus standing alone, then you should be able to live with a Milvago chimango too.  If you must place chimango into Phalcoboenus, please don't label everything Daptrius.  Thanks!"

Comments from Pacheco: “NO. I consider the comments of Sergio perfectly pertinent. For all these reasons, I defend also that Chimango Caracara deserves a monotypic genus. Something like "Protodaptrius" to be published by someone.”

Comments from Stiles: “NO. Here, I tend to agree with Sergio: lumping everything into Daptrius produces a virtually undiagnosable soup, and I tend to dislike the “toss the whole mess into the same bag” approach, as it also implies sweeping a lot of useful biological information under the rug. As I am not very familiar with either Phalcoboenus or chimango (especially their plumage sequences) and given the weak support for lumping the latter into the former, I’d rather see a new genus for chimango if the differences are as great as appears. Ibycter is clearly OK as a monotypic genus. The only real surprise to me is the relatively close relationship indicated between Daptrius ater and Milvago chimachima. To me, they are very different birds in habitat, sociality, plumage sequences and foraging: about the only similarities are that they both “scream”, and a rather general resemblance in shape. Like Manuel, I certainly don´t consider D. ater an “open country” bird. Hence, I tend to favor option 4, though it would be nice to have better genetic data to assure the placement of chimango.”

Comments from Pérez-Emán: “NO. I am familiar with both Daptrius ater and Milvago chimachima but not much with Phalcoboenus and M. chimango, so comments from Sergio, Pearman and Nacho are particularly useful to evaluate this proposal. Fuchs et al. (2012) phylogenetic hypothesis does not really support merging chimango into Phalcoboenus, so I would discard both options 2 and 3. Additionally, as Gary mentioned, ater and chimachima seem to me very different birds. I would favor option 4 as it will preserve basic differences among this group of birds, but it is contingent upon the availability of a name. Option 1, the other alternative, would group a somehow similar species of birds including some variability unique to each current genus. Differences between option 1 and 4 depends on how much variability we would want to include into a genus.”