Potential changes to North America’s bird checklist in 2021

While the American Ornithological Society addresses the issue of eponyms — bird species named for people — with a new ad-hoc committee, the regular annual work of considering changes to the taxonomy of birds goes on. The North American Classification Committee (NACC) is the body that considers proposals for species splits and lumps, higher-level taxonomic changes based on new research, additions to the main North American checklist of species after recent sightings, and any other changes necessary to keep the checklist up to date.

Last year, the NACC split Mexican Duck from Mallard and lumped Northwestern Crow with American Crow, among other changes.

The NACC will likely announce its 2021 checklist decisions in June or July, but thanks to the proposals that are posted on its website, we already know what topics it’s looking at. Here are a few of the proposals that caught my eye as the most relevant to birders:

Split Mew Gull. This suggestion would recognize the North American subspecies brachyrhynchus as a full species, separate from subspecies in Europe and Asia. The North American birds breed in Alaska and western Canada and winter mostly along the Pacific coast. The proposal also calls for the common name to be Short-billed Gull.

Split Band-rumped Storm-Petrel. A recent study shows significant genetic differences among the various populations of this seabird. The suggestion is to split it into three species: Hydrobates castro, which is widely distributed in the North Atlantic; Hydrobates jabejabe, a year-round breeder on the Cape Verde Islands; and Hydrobates cryptoleucura, widely distributed in the Pacific and South Atlantic Oceans. The common names for the first two could be Madeiran Storm-Petrel and Cape Verde Storm-Petrel; it’s not clear what the third bird’s common name may be.

Split Magnificent Frigatebird. This proposal would split the birds that breed on the Galápagos Islands from the other more widespread Magnificent Frigatebirds of the Pacific and Caribbean. This idea seems unlikely to pass at this time because the South American Classification Committee considered the same proposal, and all members voted against it. However, it may be revisited in the future as members of the committee suggested they’d like to see more detail about frigatebird genetics.

Split Bahama Nuthatch. Recent genetic studies reveal distinct differences between this bird and the mainland Brown-headed Nuthatch, suggesting the Bahama birds be split. After Hurricane Dorian in 2019, however, Bahama Nuthatch may already be extinct.

Lump McKay’s Bunting with Snow Bunting. McKay’s Bunting breeds only on St. Matthew and Hall islands in the Bering Sea and winters along the coast of western Alaska. While the male McKay’s appearance is different from the more widespread Snow Bunting, its song and call are similar, and a recent genetic study found “no fixed differences between the species.” The proposal suggests McKay’s be considered a subspecies of Snow Bunting.

Possible genus change for Ruby-crowned Kinglet. This proposal is notable because it suggests that Ruby-crowned Kinglet is not all that closely related to Golden-crowned Kinglet, despite their similar common names. Ruby-crowned’s scientific name is Regulus calendula. Golden-crowned Kinglet is in the Regulus genus, too, as are the Goldcrest and Firecrests of Europe and Asia. (Could those species names be any cooler?) Anyway, as long ago as 1853, naturalists noted how Ruby-crowned’s plumage and other aspects of its anatomy differ from the other Regulus species, so it was put in its own genus, Corthylio. However, since the first American Ornithologists’ Union checklist back in 1886, it has been a part of Regulus. The proposal that the NACC is considering suggests assigning the Ruby-crowned to Corthylio again because DNA evidence shows that it diverged from the other kinglet and crest species around 15 million years ago. If adopted, this wouldn’t affect the common English names of either of our kinglets, but it would give us a better understanding of the evolutionary relationships of these common and delightful migratory songbirds.

A version of this article will be published in “Birding Briefs” in the July/August 2021 issue of BirdWatching magazine.