Listing & Taxonomy

2021 AOS Classification Committee Proposals, Parts 2 & 3

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 past years, we offer the second and thirds chunks 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.

As before there are a couple things to note, including the usual caveat that these are just proposals and the committee has yet to announce their decisions formally. There are some that are unlikely to make the cut for whatever reason–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. 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.


Revise the linear sequence of passerine families

A proposal name like this suggests lots of big changes. Sparrows in front of warblers! Nuthatches at the end of our bird books! But the changes are fairly minimal.  The largest, in that it impacts the most species, puts Tyrant Flycatchers in front of the neotropical antbird family, which would really only affect bird books from Mexico south as there are no antbirds on the ABA Checklist despite an old Barred Antshrike record from Texas.


Recognize Basileuterus delattrii as a separate species from Rufous-capped Warbler B. rufifrons

Rufous-capped Warbler is an increasingly regular breeder in the ABA Area in southern Arizona. The species consists of 8 described subspecies found throughout Mexico and Central America with northern and southern groups differing in both vocalizations and the extent of yellow on the birds’ underparts. This proposal states that the more extensively yellow delattrii group found from Guatemala south into northern Colombia should represent a full species, called Chestnut-capped Warbler. Though the AOS has a rule stating that, in the event of a split, both daughter species are assigned new names, this rule is inconsistently applied. The authors suggest that Rufous-capped Warbler be retained for the Mexico and north birds, though Rusty-capped Warbler is put forward as a similar but sufficiently different name for the ABA Area birds.

Be it rufous or rusty, it’s still a sharp-looking little bird.


Change the spelling of Porphyrio martinicus to P. martinica

Who doesn’t love sorting out the weird quasi-latin language of scientific names? Purple Gallinule has, for many years in many books, checklists, etc, had the name Porphyrio martinicus, referring to the Caribbean island of Martinique on which the first specimen of this colorful rail was taken. The question is, evidently, whether the word is to be used as a noun, describing the island, or an adjective. It is further confused by the fact that both martinica and martinicus have been used widely, the former on the ABA Checklist and the latter in eBird, notably. The South American Checklist committee switched to martinica of late, but the NACC remains a holdout for the -us ending potentially resulting in both bodies using a different spelling to refer to the same bird. And you thought eponyms were nuts! Linneaus, despite his role in establishing this madness, has remained silent on the matter for several hundred years.


Treat Cistothorus stellaris as a separate species from C. platensis

Many authorities already consider the two populations of Sedge Wren, one a migratory bird of eastern North America and another disparate non-migratory population of Middle and South America, to be two species, and possibly even three, following a paper in 2014 that described the differences in behavior and song. The NACC has resisted this change owing to a lack of published evidence, which they note in this proposal. Even so, the tide seems to be turning in favor of this split already accepted by the South American committee. Because Sedge Wren is well-established in North America, the name is unlikely to change (see what I mean about inconsistent?), with the Middle and South American birds known as Grass Wren.


Treat Eurasian Blackbird Turdus merula as four species

Eurasian Blackbird is a wide-ranging migratory Turdus thrush that is increasingly recognized as consisting of at least four full species, with the nominate merula subspecies found from Europe and across to central Asia being the most wide-ranging. The species is a very rare vagrant in the ABA Area, with records from Quebec, Ontario, and Newfoundland, as well as many in nearby Greenland. All these bird likely represent the nominate subspecies, though it is not out of the realm of possibility that one of the east Asian subspecies, now proposed to be treated as a full species, could turn up in Alaska or even down the Pacific coast of North America. The name Eurasian Blackbird is widely retained for this species and would likely remain in the event of this proposal’s acceptance, though honestly European Blackbird would probably work too


Revise the taxonomy of the Estrildidae

The Estrilids are a family of 140-odd small finches that live primarily in the tropical Old World. There are a handful of them, however, that have established populations in the ABA Area, most notably the Scaly-breasted Munia in southern California and a couple of the waxbills in Hawaii. This is another one of those “fresh looks” at a family studies, that rearranges their taxonomic order and gives them new genera. But since most s0-called “North American” field guides don’t cover Hawaii birders in the ABA Area probably won’t notice that Lavender Waxbill would get a new genus.


Transfer Spruce Grouse Falcipennis canadensis to Canachites

The genial, needle-eating fool chicken of the boreal north has long been placed in the genus Falcipennis along with the Old World Siberian Grouse. Genetic work on the whole grouse-y group has suggested that these two species are not quite as closely related as we thought, with the Spruce Grouse and Franklin’s Grouse of the pacific northwest (a former full species that was lumped and may well be split again down the road). Turns out Spruce Grouse might actually be more closely related to the Capercallies and the Black Grouse than to the superficially similar Siberian Grouse. And if we’re not going to lump all those birds into one genus, we should at least split the Spruce Grouse (and maybe eventually Franklin’s Grouse) into Canachites.


Transfer Five-striped Sparrow Amphispiza quinquestriata to Amphispizopsis

Five-striped Sparrow is a large, striking sparrow found mostly in western Mexico but sneaking up into the ABA Area in southeast Arizona. Its location in the sparrow phylogeny has always been vexed, placed among birds now in PueceaAimophila, and Amphispiza, but through all of that, its similarity to Black-throated Sparrow seems to cut through both physical and genetic observations. A recent wholesale genetic exploration of the North American sparrows sheds a little light on things, suggesting that Five-striped is part of a clade that consists of Black-throated Sparrow, Lark Sparrow, and Lark Bunting. All three of those species are sole members of their own genera, and so Five-striped deserves as much as well and should be given the prolonged name Amphispizopsis quinquestriata. 


Add Common Wood-Pigeon Columba palumbus to the Main List

Add Pallas’s Gull Ichthyaetus ichthyaetus to the Main List

Add Pallas’s Grasshopper-Warbler Helopsaltes certhiola to the Main List

Add Tricolored Munia Lonchura malacca to the U.S. List

The house-keeping part of the proposal document. All four species were added to the ABA Checklist in the last year, Pallas’s Gull and Grasshopper-Warbler from vagrants found in Alaska, Common Wood-Pigeon from a vagrant in Quebec, and Tricolored Munia, the rare vagrant from an introduced population, seen in Florida from a established population in Cuba. Just as the ABA Checklist incorporates decision made by the NACC into our checklist, so does the NACC accept decisions of the ABA Checklist Committee. Because Cuba is already part of the AOS’s jurisdiction, Tricolored Munia is added to the United States List.


Treat Catharus swainsoni as a separate species from C. ustulatus

Birders in the ABA Area may be so preoccupied with distinguishing Gray-cheeked from Swainson’s Thrush that they might be forgiven for being unaware that Swainson’s Thrush itself consists of two field identifiable subspecies. The so-called “olive-backed” thrushes of the swainsoni group, which breed across Canada in the higher elevations of the Rockies and winter in northern South America, and the “russet-backed” thrushes of the ustalatus group, which breed along the Pacific coast and winter in southern Mexico and Central America.  The two taxa were originally described as separate species, though treated as conspecific by most authorities from the 1900s on. It has been well-established for decades that, despite a narrow contact zone in central British Columba the two species differ in habitat preferences and plumage characteristics, though differences in song are more difficult to discern owing to wide individual variation in both groups. More, they don’t appear to overlap in migration route and wintering range.

All that said, this is described as a classic “gray area” where the criteria might speak to ornithologists differently based on how they define a species. Though it should be noted that the criteria is similar to the last split in the Catharus genus, that of Bicknell’s Thrush from Gray-cheeked Thrush.


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.



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