Ever since 1886, North America’s top organization for scientific bird study—now called the American Ornithological Society (AOS)—has maintained the official list of North American bird species. It’s a great benefit to have a standardized set of names that we can all use. But names may change when species are reclassified, which happens more often today as genetic studies reveal surprises about how birds are related.
Every summer the AOS publishes a supplement to their list, detailing any revisions. And every summer, birders wait to see how the changes will affect their life lists. With the 2025 supplement, published August 14, many birders will add one or two species to their totals.
Two Vireos for One
The cheerful, lilting songs of Warbling Vireos are familiar sounds in summer from coast to coast. Alert observers had noticed that western and eastern songs were somewhat different, and now detailed studies confirm that two species are involved: Western Warbling-Vireo (Vireo swainsoni) and Eastern Warbling-Vireo (Vireo gilvus).
In most places, birders will distinguish the two by geography. Where their breeding ranges come together, along the eastern edges of the Rockies, song will be the best clue. The Eastern Warbling-Vireo sings a longer song (two to three seconds or more), with many fast syllables and with rising notes in the middle and again at the end. The Western Warbling-Vireo often sings a shorter song (less than two seconds), with fewer and slower syllables, ending on a lower note.
Separating the two visually will be more problematic—they look very similar. The western species tends to be slightly smaller, with a thinner bill, and with more of an olive-green tinge on the back. These are subtle points, and both species are quite variable. For most birders, the best way to confirm the two warbling-vireos for our lists will be to visit their breeding ranges in summer.
Herring Gull Split
The large, white-headed gulls of the world make up a complicated group. Experts have suggested for years that the bird known as Herring Gull consisted of more than one species, and this year it becomes official, as it is split four ways.
Almost everywhere in North America, the American Herring Gull (Larus smithsonianus) is the expected one. In parts of western Alaska, however, it’s outnumbered by the bird now called Vega Gull (Larus vegae), very similar but with a darker gray back in adult plumage. Vega Gulls are scarce visitors in southern Alaska and along the Pacific Coast, and wanderers have turned up elsewhere, even as far afield as Florida. A third species, the European Herring Gull (Larus argentatus), is a very rare visitor to eastern Canada, with a few records in the eastern United States.
In general, almost anywhere on this continent, it’s safe to assume any Herring Gull we see is the American species. North American birders who want to try to identify a Vega Gull (away from western Alaska) or a European Herring Gull will face an extreme ID challenge. Fortunately, the fourth member of the four-way split, the Mongolian Gull (Larus mongolicus), is a bird of central and eastern Asia, and hasn’t been found in North America—yet!
The New Amazons
Several species of parrots of the genus Amazona, escaped from captivity, live in a feral or wild state around various southern U.S. cities. The group name for these birds is changing from “Parrot” to “Amazon,” to match long-standing usage among aviculturists and others. Among the species most frequently seen are Red-crowned Amazon and Yellow-headed Amazon (in both Los Angeles and southern Texas) and Orange-winged Amazon (Miami region), but Lilac-crowned Amazon, Red-lored Amazon, and others are also present.
New Names, New Order
Other revisions announced this year were of two types that aren’t so noticeable to birders: changes in scientific names and changes in the sequence of birds on the list.
Scientific names are supposed to serve as permanent labels, but they change when a species is moved from one genus to another—as may happen as a result of new genetic studies. For example, the American Goldfinch was once classified in the genus Carduelis, along with the European Goldfinch. Then studies showed that these two were not close relatives after all, and the American Goldfinch changed from Carduelis tristis to Spinus tristis. Shifts like these don’t make much difference for birders in the field. But here are this year’s new names:
Spotted Dove (introduced in southern California): Streptopelia chinensis becomes Spilopelia chinensis.
Cooper’s Hawk: Accipiter cooperii becomes Astur cooperii.
American Goshawk: Accipiter gentilis becomes Astur gentilis.
Bluethroat: Cyanecula svecica becomes Luscinia svecica.
Fan-tailed Warbler: Basileuterus lachrymosus becomes Euthlypis lachrymosa.
Another long-term trend involves changing the order in which birds are listed. The official list supposedly follows a sequence from the most primitive kinds to the most highly evolved, while grouping related species together. It’s a fine idea in theory, but research keeps changing our concepts of the relationships among bird groups.
For decades in the 20th century, for example, the checklist began with loons and grebes, and ended with longspurs, which were considered part of a big family including grosbeaks and sparrows. But changes began to accelerate in the 1980s, and now the loons are one-third of the way down the list, nowhere near the grebes, and the longspurs are in their own separate family and far from the end of the list.
This year’s changes will continue to shift the order of our checklists. For example, rails had been listed before the Limpkin, which was followed by cranes. The new sequence will put Limpkin and cranes before rails. One series of families had gone from pelicans to herons and egrets and then to ibises and spoonbills. In the new version it will be ibises and spoonbills first, then pelicans, then herons and egrets. Within the gull family, the order had gone like this: gulls, noddy terns, typical terns, Black Skimmer. In the new order, the gulls flip to last, after the noddy terns, typical terns, and Black Skimmer. So as checklists are updated, birders who had memorized the old order will have to spend a little more time hunting around for names.
Hawai‘i and the Tropics
The area treated by the AOS includes Hawai‘i and extends south through Central America and throughout the Caribbean, and some changes were announced from those regions as well. The beautiful White Tern has been split into three species, and the one nesting in Hawai‘i is now called Blue-billed White-Tern (Gygis candida). The scientific name of the Greater Necklaced Laughingthrush (established on Kauai) changes from Garrulax pectoralis to Pterorhinus pectoralis. South of the Mexican border, several birds including Squirrel Cuckoo, Nutting’s Flycatcher, Black-throated Trogon, and Plain Xenops have each been split into two or more species. Birders who have traveled in the tropics, and have kept track of where they saw various birds, may find that this year’s supplement gives them “armchair” additions to their world life lists.
