2020 AOS Classification Committee Proposals, Part 1

As we have in the past, here is the first rundown of the new bird taxonomy proposals submitted to the American Ornithological Society’s North and Middle America Classification Committee for 2020. The AOSNMACC is the volunteer group of ornithologists who make the split, lump, and name-change decisions that influence the ABA Checklist and our field guides.

We suggest the usual caveat that you are undoubtedly familiar with by now, that it’s important to note that these are just proposals and the committee has yet to vote on them formally. There are some that are unlikely to make the cut for whatever reason, but in my opinion the proposals are often more interesting than the actual results anyway as we get a peek into the wild world of bird taxonomy as it exists from year to year.

This post will only mention those changes that affect the ABA Area, but if you’re interested in every single one of the proposals– the committee’s jurisdiction includes all of the North America south to Panama – please refer to the official list of proposals at the AOS’s website (.pdf).


Change the English name of Olive Warbler Peucedramus taeniatus to Ocotero

Olive Warbler is famously one of the worst bird names in North America, as it is neither olive nor a paruline wood-warbler, as recent genetic research has made abundantly clear. In fact, the Olive Warbler is far more interesting than all that, being the sole member of the family Peaucedramidae. It has become something of a convention to give the birds in these single-species families a one word name as befits their genetic uniqueness, and Ocotero has been suggested here as it is a name that is already in use across much of the species Latin American range, as it is derived from ocote, a colloquial Spanish name given to pine trees in which this bird is frequently found. As such, it highlights the bird’s habitat and behavior in addition to its evolutionary uniqueness.


Change the generic classification of the Trochilini

We’ve become accustomed to proposals concerning potential rearrangements of the taxonomic order in these reports. This becomes necessary as our ability to parse the genetics of various bird families and genera becomes more sophisticated. Trochilini is a very big group of hummingbirds, continuing over 100 species, and as such, this is a big proposal even if its impact on ABA Area birders is fairly light.

The seven species of hummingbirds on the ABA checklist included in this group are the ABA Area breeding Broad-billed Hummingbird, Buff-bellied Hummingbird, Violet-crowned Hummingbird, and White-eared Hummingbird along with vagrants Berylline Hummingbird, Cinnamon Hummingbird, and Xantus’s Hummingbird will likely see their placement in the checklist relative to each other arranged in some fairly modest way. But rest assured, there are some big doings going on south of the border.


Recognize Mexican Duck Anas diazi as a species

Taxonomy fans might remember that this split was also proposed last year, and it was not accepted. The basic facts are more or less unchanged. Mexican Duck is one of those cryptic Mallard-like species that have always been problematic from a species standpoint. All of the various Mallard and Mallard-like duck species are known to interbreed with Mallards readily, particularly as non-migratory populations of Mallard have become the norm, but in the case of Mexican Duck it appears that that hybridization is not as extensive as was formerly believed. Or, at least, it appears that the levels of genetic divergence in diazi is at a higher level than any of the other full species in the New World Mallard complex. In fact, Mexican Duck appears to be more closely related to American Black Duck than to Mallard, and it may be more accurate to say that diazi is a western counterpart to the former as opposed to a southwestern form of the latter. This proposal adds another study to the mix and asks that the AOS reconsider their decision. This split would add a species to the ABA checklist.


Split Royal Tern Thalasseus maximus into two species

“An armchair tick!”, you might be quick to exclaim upon reading the title. But this proposal does not suggest splitting subspecies in the Americas, but splitting the nominate subspecies that ABA birders are no doubt familiar with from a population in west Africa. Those African birds, as it turns out, are not really that closely related to the Royal Terns of the Americas despite their physical similarities. Our Royal Terns are most closely related to Sandwich Terns whereas the African birds are a sister species to the Lesser Crested Tern of Asia and should be split with the new name African Crested Tern.


Recognize Great White Heron Ardea occidentalis as a species

The Great White Heron of south Florida and the Caribbean was, for more than 100 years, considered a full species until it was lumped with Great Blue Heron in 1973 (a famously lumpy checklist year). The proposal suggests that the evidence for that lump was weak and that Great White Heron should no longer linger as a range-restricted color morph of the widespread Great Blue Heron. Hybrid birds (long known as Würdemann’s Heron) are not, in fact, a subspecies but a population of hybrid birds as one would expect in the contact zone. A contact zone that closely resembles those of other closely related species like Lazuli/Indigo Buntings and Rose-breasted/Black-headed Grosbeaks. This split would add a species to the ABA checklist.


Modify the linear sequence of species in the Phalacrocoracidae

Yet another revision of the taxonomic order, this time concerning cormorants and mirroring a recent decision made by the South American Checklist Committee.


Modify various linear sequences to reflect new phylogenetic data

And in the housekeeping vein, the last proposal is mostly a grab-bag of various taxonomic revisions recently accepted by the South American Classification Committee. Expect minor changes to the taxonomic sequence of boobies, vultures, rails, and gulls.


The full list, including background information and recommendations is available here (.pdf). Stay tuned for the results of the voting this summer. May the splits be with you.

Nate Swick is the editor of the American Birding Association Blog, social media manager for the ABA, and the host of the American Birding Podcast. He lives in Greensboro, North Carolina, with his wife, Danielle, and two young children. He is the author of Birding for the Curious and The ABA Field Guide to Birds of the Carolinas.