2021 AOS Classification Committee Proposals, Part 1

There are few constants in these helter-skelter times, but the birding world can always depend on the bird taxonomy proposals submitted to the American Ornithological Society’s North and Middle American Classification Committee. And as we have done in years’ past, we offer the first chunk of the new bird taxonomy proposals submitted to the the AOS-NACC, the volunteer group of ornithologists who make the split, lump, and name-change decisions that influence the ABA Checklist and our field guides.

A couple things to note, including the usual caveat 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 we share them anyway because proposals are often more interesting than the actual results because we get a peek into the wild world of bird taxonomy as it exists from year to year. But also, that the common name proposals that we typically see scattered throughout are to be bundled and dealt with separately. The Birds Names for Birds movement, which argues for changes in bird honorific names, has resulted in a great many proposals submitted this year to that end and the AOS NACC has announced they will address them at a later time, though that time is, as yet, unknown.

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.


Split Band-rumped Storm-Petrel Hydrobates castro into three species

Seabird taxonomy is famously something of a black box, but it’s perhaps better described as a black box inside that original black box. Not only is it frequently difficult to reach breeding colonies on far-flung specks of rock in the middle of the ocean, but similarities in size and plumage made field identification extremely difficult unless you are on those islands. Band-rumped Storm-Petrel is maybe the classic example of this phenomenon, a group of birds ranging across both the Atlantic and Pacific Oceans that are thought to contain, at minimum, seven named taxa, including those that breed on the same islands in the same burrows, but at different seasons. What a mess.

The NACC is tasked to consider a massive study that attempts to untangle this long-standing problem and does to a degree. So it might come as something of a surprise that the impact on the ABA checklist is somewhat minimal. The Gordian Knot that is the North Atlantic group of birds is still mostly tied tight, but those Band-rumps in the Pacific and South Atlantic, consisting of the subspecies cryptoleucura, along with bangsi, kumagai, and helena, is likely a good split. It’s hard, however, to come up with a name for such a wide-ranging group. This would add one species to the ABA Checklist, as cryptoleucura breeds in Hawaii and has occurred, at least once, in California waters.


Split Mew Gull Larus canus brachyrhynchus and rename as Short-billed Gull

What we think of as Mew Gull is actually one of four subspecies of the near-holarctic Larus canus, widely known as Common Gull in the Old World. Birders in North America have, in practice at least, treated them as separate species, even though the two populations have been lumped since 1931. The new work considered by the committee finds fairly conclusively that, at minimum, the European canus birds and the western North American brachyrhynchus birds should be considered separate species, but the presence of the East Asian kamschatschensis populations, known to western vagrant hunters as “Kamchatka” Gull makes things a little more complicated. In any case the proposal suggests treating all of the Old World subspecies together as Common Gull and adopting Short-billed Gull for our North American birds, arguing that Mew Gull, while currently established just for the North American population, was historically used for all of them. Short-billed Gull is a familiar alternate name for Mew Gull and a direct translation of the scientific subspecific. Plus, it’s not a bad field mark. This would add one species to the ABA Checklist, as Common Gull is a regular vagrant on the East Coast of North America.


Revise generic limits in the Phalacrocoracidae (cormorants)

We’re used to seeing these sorts of taxonomic revision proposals, but this one is a tad different in that it would result in some new genera for some familiar species. All North American cormorants are nestled in the genus Phalacrocorax, as are just over half of the entire family. Recent genetic work on the family found that all North American cormorants, save Great Cormorant, settle into well-defined groups. Neotropic and Double-crested (along with the Flightless Cormorant of Galapagos) in one, and Red-faced, Pelagic, and Brandt’s in another. Acceptance of this proposal would see changes to cormorant genera, with Nannopterum for the former group and Urile for the latter.


Change the linear sequence of the gnatcatchers (Polioptila spp.)

A completely inoffensive revised sequence for these hissy little passerines. The only change to the ABA Checklist sees California Gnatcatcher and Black-tailed Gnatcatcher switch places.


Split Fregata rothschildi from Magnificent Frigatebird F. magnificens

Magnificent Frigatebird is a widespread species in the tropical Americas and is regularly seen in the ABA Area in Florida and the Gulf of Mexico, and infrequently in Southern California. The breeding population on the Galapagos Islands was long considered to be part of this wide-ranging and dispersal prone species, but work on the mtDNA shows that the Galapagos breeding birds are really really different with surprisingly little gene flow.

I included this proposal in this post, despite typically restricting it only to ABA relevant proposals, for two reasons. The first, there is an outside chance that it would require a name change for our familiar Magnificent Frigatebird, though it seems far more likely that the committee will make the more sensible choice to retain that common name for the widespread species and name the Galapagos population “Galapagos Frigatebird”. And second, given the dispersal abilities of frigatebirds, it’s not out of the realm of possibility that a Galapagos Frigatebird could show up in the ABA Area, as records already exist from coastal Central America.


Resurrect Corthylio for Ruby-crowned Kinglet

Kinglet enthusiast know that the spunky Ruby-crowned Kinglet is quite unique from the the rest of the genus Regulus, which consists of various Gold/Firecrest lookalikes. More than just their appearance, Ruby-crowned Kinglets differ in vocalizations and foot morphology, too. A look at their mtDNA suggests that the Ruby-crown is unique among the genus, but whether that means it deserves its own genus, the resurrected Corthylio, is a matter of where you want to draw the line between genus and species. Either way, it’s different, and the uniqueness would see it, at very least, moved to the top of Regulus as befits this cute little oddball.


Change the linear sequence of species in Chaetura

The genus Chaetura is represented in the ABA Area by two very similar species, Chimney Swift and Vaux’s Swift, so much of the impact of this proposal re-evaluating swift genetics would be seen in the tropics. For ABA Area birders, it would see Chimney and Vaux’s switch places in most checklists.


Reconsider the case to split Saxicola maurus and S. stejnegeri from Common Stonechat S. torquatus

This is an interesting one that attempts to bring North American taxonomic authorities into alignment with Old World authorities. Saxicola torquatus is listed on the ABA Checklist as Stonechat on the basis of a handful of Alaska records and single records from California and New Brunswick. Stonechat has long been a headache for Old World birders, with upwards of 6 named subspecies depending on the authority, but with clear separation between birds in the East Asia, the Central Asia and Europe, which along with the African subspecies break roughly into full species status for European Stonechat (S. rubicola, Europe), Siberian Stonechat (S. maurus, central Asia), African Stonechat (S. torquatus, Africa), and Amur Stonechat (S. stejneger, East Asia), with the possibility that maurus and stejneger could be retained as a single species.

What this means for the ABA Area is a little more fun. The records from Alaska and California are almost certainly stejneger, called either Siberian Stonechat or, in a four-way split, Amur Stonechat. In fact, most of the Alaska records have been identified as such. But what of the New Brunswick bird? Could that individual, photographed in 1983 with the limitations of 80s era technology, be rubicola, and thus add a bird to the ABA checklist? For their part, Howell and Russell in Rare Birds of North America, don’t think so. The East Asian Stonechats are long-distance migrants, the European ones less so. So it’s just as likely that a bird from East Asia made the long journey to eastern Canada, a sort of pattern we’ve seen before. At best, it’s likely to remain inconclusive and the ABA Checklist will just see a name change instead of a +1.


Treat McKay’s Bunting Plectrophenax hyperboreus as conspecific with Snow Bunting P. nivalis

A lump! We haven’t seen these terribly often in recent years and this seems to be a fairly straightforward one. The range restricted McKay’s Bunting has been treated as a full species since 1886, though even back then that designation was questioned. This proposal is unique in that it doesn’t have a significant genetic component, arguing that, because there are no isolating mechanism, the birds seem to interact with one another freely, and the much-heralded plumage differences are within variation of either species, to which anyone who has tried to pick out a McKay’s Bunting from a flock of Snow Buntings in western Alaska can readily attest. Thus, McKay’s Bunting should be considered an endemic subspecies of Snow Bunting.

On the side of retaining full species rank, the proposal notes that Snow Buntings are very rare on St. Matthew Island where McKay’s Breed, and differences in migration timing keep them from interbreeding, though documentation of this is spotty. Who knows how this one will play out, but if successful it will see a species removed from the ABA Checklist.


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