Warbling Vireo split into Eastern and Western

What changed

Who decided, and when

• August 14, 2025American Ornithological Society (AOS): the 66th Supplement to its Check-list of North American birds
• September 11, 2025American Birding Association (ABA): followed the AOS on the ABA Checklist
• October 2025eBird and the Clements Checklist: its 2025 taxonomy update
• June 11, 2026AviList, the shared world checklist: version v2025b still has one Warbling Vireo; a split is among the questions it is considering

Which one did you see?

Mostly by where the bird nested. In summer, Warbling Vireos from the Rockies west are Western; those on the Great Plains and in the East are Eastern. The two meet along the eastern edge of the Rockies, from Alberta down to Colorado.

They look almost the same, so the song helps most. Eastern sings a longer, rambling song that rises at the end. Western's song is shorter and doesn't end on that high note.

A bird seen on migration, away from where it nests, is hard to place. You can log it as “Eastern/Western Warbling Vireo”, which keeps the sighting but doesn't count as a species.

What it does to your list

If you have seen Warbling Vireos on only one side of the Rockies, nothing changes but the name. If you have seen them on both sides, eBird now counts two species, so your total goes up by one.

When eBird can't tell which of the new species an old record was, it keeps the sighting as a “one or the other” record. Those stay in your records but don't count as a species.

Your Birdfolio follows AviList, which still has one Warbling Vireo. If eBird shows two and your book shows one, a notes page in the book explains why.