Proposal (805) to South American Classification Committee

Recognize family rank for Herpetotheridae, Polyboridae and Falconidae within the order Falconiformes

Effects on South American CL: This proposal would recognize family-level taxon for three clades of birds within Falconiformes.

Background: Currently SACC classifies diurnal raptors in three separate orders: Cathartiformes, Accipitriformes and Falconiformes, based on the results of recent molecular studies. If Cathartidae and Accipitridae ascends to ordinal rank, Falconidae would ascends also, even when Falconiformes already exist. Up to date, SACC recognize that Falconiformes include only one family: Falconidae, which contains Herpetotherinae and Falconidae subfamilies, unrecognizing Polyborinae. With the ascension of Falconidae to ordinary rank, the subfamilies would ascend to family rank, but this has not been considered. Some authorities as Ferguson-Less & Christie (2001) adopt the same criteria to ascend the three subfamilies within Falconidae to family rank, following the ascension of Falconidae to Falconiformes, although they named the caracaras as Daptriidae.

New information: Following the most recent and comprehensive molecular works on the Falconidae group done by Fuchs et al. (2011, 2012, and 2015); the group are conformed by three distinctive subfamilies: Herpetotherinae (Forest-falcons and Laughing Falcon), Polyborinae (Caracaras and Spot-winged Falconet) and Falconinae (Falcons and falconets).

Recommendation: Even when taxonomy should reflect phylogenetic relationships, the current classification of major clades, such as orders, is more pragmatic, and do not reflect necessarily the time in which those groups radiate (all the orders differ of each other at different times). In my view, that pragmatic practice should be used also in lower classification levels such as families. Therefore, even when Herpetotherinae is basal to the other two groups within Falconidae: Polyborinae and Falconinae, these three groups are sufficient distinctive to be considered subfamilies (Fuchs et al. 2014). I first recommend recognizing Polyborinae as a subfamily of Falconidae, together with the other two subfamilies: Herpetotherinae and Falconinae. This is based on well-supported cladistics divergence (Fuchs et al. 2014) and extremely different lifestyles: The basal group of forest falcons are very specialized predators that live in dense forests and have distinctive morphologic characters similar to those of Accipiters, true falcons are agile and fast predators most of them living in open habitats, while Caracaras have terrestrial opportunistic habits and diet. Secondly, I recommend ascending all these three subfamilies to family rank, following the ascension of the family Falconidae to ordinal rank. These new classification allows separating three clades of raptors with very different natural histories within Falconiformes.

Literature Cited:

Ferguson-Less, J. & D. A. Christie. 2001. Raptors of the World. Princeton University Press. USA

Fuchs, J., S. Chen, J. A. Johnson & D. P. Mindell. 2011. Pliocene diversification within the South American Forest falcons (Falconidae: Micrastur). Molecular Phylogenetics and Evolution 60: 398-407.

Fuchs, J., J. A. Johnson & D. P. Mindell. 2012. Molecular systematics of the caracaras and allies (Falconidae: Polyborinae) inferred from mitochondrial and nuclear sequence data. Ibis. Doi: 10.1111/j.1274-919X.2012.01222.x

Fuchs, J., J. A. Johnson & D. P. Mindell. 2015. Rapid diversification of falcons (Aves: Falconidae) due to expansion of open habitats in the Late Miocene. Molecular Phylogenetics and Evolution. 82: 166-182.

Tomás Rivas-Fuenzalida, May 2018

Comments from Remsen: “NO. All of these groups have formal higher-level names already, and no objective rationale is presented for why they should be changed.”

Comments from Areta: “NO. I don´t see anything wrong in the families as currently defined and sub-familial and generic groupings seem good enough to sort out variation within Falconidae.”

Comments from Stiles: “NO, for the reasons given in the preceding proposal - and reinforced by the implication of late Miocene diversification among the Falconidae, which I think is to recent to justify this proposal.”

Comments from Claramunt: “NO. I don’t see compelling arguments supporting the proposed change, so I favor the traditional ranking. One argument that transpires from the proposal is the redundancy between the categories Falconiformes and Falconidae, which contain exactly the same taxa. To some degree, for some taxa, this situation is unavoidable (e.g. Opisthocomidae) but a classification in which Falconiformes contains three families would be more balanced, in that sense. However, I’m not convinced that the current Falconidae can be split in a satisfactory way in multiple family-rank taxa. The phenotypic gap is greatest between the caracaras and Falco. But, in my mind, birds like Spiziapteryx and Micrastur bridge that gap. In summary, I think that this is a proposal that we could reconsider in the future with more ancillary data at hand (quantitative phenotypic data analyses, divergence times).”

Comments from Pacheco: “NO. Any objective justification is not provided as to why they should be changed.”

Comments from Zimmer: “NO. As others have stated, there is no compelling justification given for making this change, given that currently defined subfamilies and generic grouping already provide a logical framework for sorting out the variation within Falconidae. The part of the proposal that I would be most sympathetic to is the idea of recognizing “Polyborinae” as a subfamily on a par with Falconinae and Herpetotherinae. Some time back, we passed Proposal #281, which added subfamily structure to Falconidae, and also rearranged the linear sequence. That proposal resulted in the recognition of Falconinae (caracaras + Falco) and Herpetotherinae (Micrastur + Herpetotheres) based upon non-controversial genetic analysis that showed a deep division in Falconidae. In that Proposal, Van suggested that we could follow up by “also recognizing a major split within Falconinae with tribe designations (Falconini and Caracarini) but that should be a separate proposal.” As far as I can tell, we never followed up on that issue, and, I think the argument could be made that we should. From a natural history/ecological perspective and phenotypic perspective, I think that the differences between caracaras and Falco are on a par with those between Herpetotherinae and Falconinae, even if the former is basal to everything else. I think we should recognize that split at some level, either with tribal designations, or, as suggested in the present Proposal, by recognizing Polyborinae as a subfamily within Falconidae.”

Comments from Robbins: “NO, again for the same reasons that were expressed by committee members in proposal 804.”

Comments from Stotz: “NO. Very similar to issues is proposal 804. Again, based on current knowledge, it does not appear there is anything to be gained by changing the rank of the currently recognized subfamilies to family level.”