American Birding Podcast



2018 AOS Classification Committee Proposals, Part 3

This is the third and likely final batch of bird taxonomy proposals submitted to the American Ornithological Society’s North and Middle America Classification Committee, the volunteer group of ornithologists who make the split, lump, and name-change decisions that influence the ABA Checklist and our field guides.

You know the drill 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 the interests of keeping an eye on the world of bird taxonomy as it exists from year to year we’ll include all of them here regardless of how likely or likely they might be.

This post will only mention those changes that affect the ABA Area, but if you’re interested in the whole list including birds found in Middle America – 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).


Adopt (a) a revised linear sequence and (b) a subfamily classification for the Accipitridae

We’ll start with a pretty straight ahead adjustment of the non-falcon diurnal raptors. Up to now, the order of eagles, kites, and hawks was informed less by our knowledge of their genes and more by feeding ecology and morphology. As we continue to sweep away those 19th Century ideas of what is related to what, Acciptridae is due for a remodel with some interesting consequences. White-tailed Kite and Mississippi Kite, despite being mophologically similar, are actually not that closely related, for instance, and the graceful Swallow-tailed Kite belongs in a subfamily with the bizarre hook-billed Kite.


Split Yellow Warbler (Setophaga petechia) into two species

Yellow Warbler is easily the most wide ranging of its family in the Americas, breeding across nearly the whole of North America into northern South America and consisting a staggering 35 described subspecies which are broken, roughly, into three groups. Migratory ABA Area breeding birds, called American Yellow Warbler are in the aestiva group, sedentary Middle American and South American birds, called Mangrove Warbler, in erithachorides group, and Caribbean birds, commonly called Golden Warbler, in the petechia group. The proposal suggests splitting aestiva from the southern birds, based on genetic and plumage difference, both Golden and Mangrove Warblers tend to have varying amounts of chestnut on the head with erithachorides famously with the entirely chestnut head. This would add one species to the ABA Checklist, to be called either Mangrove or Tropical Yellow Warbler based on breeding records in Florida and Texas, and change the name of the familiar Yellow Warbler to American Yellow Warbler, with the possibility that erithchorides and petechia could be further split down the line.

“Mangrove” Yellow Warblers, like this bird in southern California, are quite different from the bird many of us know as Yellow Warbler. Photo: Joe Sweeney/Macaulay Library


Revise the classification and linear sequence of the Tyrannoidea

The tyrant flycatcher family is among the most diverse and largest groups of birds in the Americas. Perhaps it is because of its size that its systemics are a bit of a mess, with revisions made to parts of the family but to the whole. This proposal essentially does just that, taking the most recent available information on various tyrannids and using it to better put the puzzle together. Some new families are proposed for some of the more distinctive flycatchers, but none that affect any of our breeding birds.


Split Cory’s Shearwater (Calonectris diomedea) into two species

In recent years, seabirders in the north Atlantic have been paying particularly close attention to Cory’s Shearwaters in the hopes of picking out the smaller, paler, nominate subspecies, commonly called Scopoli’s Shearwater. Nearly all Cory’s Shearwaters in the ABA Area are of the borealis subspecies, which breeds primarily on temperate islands in the eastern Atlantic. Nominate “Scopoli’s” birds breed in the Mediterranean Sea and are less frequently, but regularly, encountered in ABA Area waters. The two groups do not appear to interbreed on any islands, and can be differentiated with careful study. The borealis birds would retain the name Cory’s Shearwater, though with a different scientific name, and the Scopoli’s Shearwater elevated to full status. No consensus seems to exist on whether that is pronounced ska-PO-li or SCAW-po-li, however.

Scopoli’s Shearwater, like this one in the waters off North Carolina, is best differentiated from Cory’s by the greater extent of white on the underside of the primaries, but they also average smaller, with a more slender head and bill. Photo: Andrew Dreelin/Macaulay Library


Split White-collared Seedeater (Sporophila torqueola) into two species

White-collared Seedeater is a small finch-like tanager species common throughout Middle America. It occurs in the ABA Area in south Texas, where it is an uncommon, but regular, breeding bird. The species currently consists of five subspecies that are separated roughly into two groups, the sharply black and white moreletti group, which contains the birds found in the ABA Area, and the more richly colored torqueola group of western Mexico. This proposal suggests a split of the two groups based on plumage, song, and genetic differences, with the west Mexican birds becoming Cinnamon-rumped Seedeater, and the white-rumped birds, including those in the ABA Area, retaining the name White-collared Seedeater. Though in my editorial opinion, White-rumped Seedeater seems a more obvious and useful name and is already in use elsewhere in the species’s range, but what are you going to do?


Lump Taiga Bean-Goose Anser fabalis and Tundra Bean-Goose A. serrirostris

The excitement of finding one of the bean-geese in the ABA Area is often tempered by the difficulty in identifying the dang thing to species. This proposal would remedy that situation by lumping them, or, rather *re*-lumping them, as the bean-geese were split only about 10 years ago in the first place. And it is that decision to split that this proposal calls into question, claiming that the then-North American Check-list Committee was premature in that decision and that the relationship between Tundra and Taiga Bean-Goose is more complicated that was known at the time. As such, the species should once again be considered together for the time being.


Recognize Mexican Duck Anas diazi as a species

One of the subspecies of the familiar Mallard in which the male and female share the same plumage, Mexican Duck has been something of a mystery as a taxon for a long time. 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 divergeance 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.

In many ways, Mexican Duck, like this bird in Arizona, appears more like a western version American Black Duck than a subspecies of Mallard. Photo: Ryan P. O’Donnell/Macaulay Library


Split Gray Nightjar Caprimulgus indicus into three species, recognizing (a) C. jotaka and (b) C. phalaena

Gray Nightjar ranges widely across east Asia and is represented on the ABA Checklist by a single, dead, individual found on Buldir Island, in the Aleutians, Alaska, in 1977. The proposal brings the AOS list in harmony with a number of other taxonomic authorities which have split the species into Gray Nightjar, C. jotaka, of East Asia, and C. phelaena, of south Asia, which is commonly called Jungle Nightjar or Indian Jungle Nightjar. The common name would remain the same but the scientific name would change accordingly.


Split Barn Owl (Tyto alba) into three species

When considered as one cosmopolitan species with 28 named subspecies, the ghostly Barn Owl is one of only a small handful of species that can be found on all six inhabited continents. However, that notoriety is under threat from new research that re-evaluates the relationships between those populations and sorts Barn Owl three well-defined clades, not unexpectedly, corresponding more or less to the continents. Barn Owls in Africa, Europe and southwest Asia become Western Barn Owl, those in Australasia and South Asia become Eastern Barn Owl, and our birds in the Americas become American Barn Owl, a name that might excite birders who use banding codes in their notes because it finally breaks the Barred Owl-Barn Owl logjam.


Split LeConte’s Thrasher (Toxostoma lecontei) into two species

The southwestern thrashers have been the subject of a lot of study to suss out their taxonomic relationships, lately. Taxonomy fans might remember a recent unsuccessful attempt to split Curve-billed Thrasher. This proposal focusing on LeConte’s Thrasher is similar, but looks at the species level bona fides of the range restricted Baja California subspecies arenicola and not any population that can be found in the ABA Area. This population does not appear to share any contact zone with other subspecies of LeConte’s Thrasher. The name Vizcaíno Thrasher is proposed, with the ABA Area birds remaining LeConte’s Thrasher.


Revise generic assignments of New World “grassland” sparrows

The grassland sparrows of genus Ammodromus are among the most loved of their family in the ABA Area, both for their often bright colors and for the satisfaction that comes with getting a good look at the sneaky little things. This proposal suggests some wholesale changes to the group, leaving the venerable genus a shell of its former self. Recent molecular work shows that the genus Ammodromus actually consists of three distinct groups, none of which are each other’s closest relatives. So solve this problem the “marsh sparrows”–LeConte’s, Saltmarsh, Seaside, and Nelson’s– are moved into the resurrected genus Ammospiza, with Grasshopper Sparrow, along with the South American Grassland and Yellow-browed Sparrows, remaining in Ammodramus.

The odd birds out, Henslow’s and Baird’s Sparrows, are a bit more complicated. Of the three options in the proposal, the one recommended would dump Henslow’s, Baird’s, the Melospiza sparrows (Song, Lincoln’s and Swamp), and Savannah Sparrow into Passerculus, which currently only contains the last of that list, a genus that would be a bit of a sparrow soup. We’ll see what happens.


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 ever in your favor.