2025 Taxonomy Update Completed
“Taxonomy” refers to the classification of living organisms (as species, subspecies, families, etc.) based on their characteristics, distribution, and genetics. There are multiple taxonomies for birds around the globe. Projects at the Cornell Lab of Ornithology—including eBird, Merlin, Birds of the World, and the Macaulay Library—use the eBird/Clements Checklist of Birds of the World, or eBird/Clements Checklist for short.
The eBird/Clements taxonomy is the backbone of all bird information available through Cornell Lab projects. Every year, the world’s taxonomic authorities propose a newly restructured avian taxonomy. Soon after the taxonomic changes are settled, the taxonomy team and editors get busy revising accounts so that the Birds of the World website reflects the new taxonomy.
Our understanding of species is constantly changing. Every year, some species are “split” into two or more, while others are “lumped” from multiple species into one, as we gain a better understanding of the relationships between birds. The eBird/Clements Checklist is updated annually to reflect the latest developments in avian taxonomy. “Taxonomy Time” is an opportunity to celebrate the many scientific advances in ornithology made over the past year— some of them thanks to your eBird data!
Yellow Warbler A big North American split, Yellow Warbler will be divided into:
• Northern Yellow Warbler (Setophaga aestiva)— the migratory northern population that breeds in shrubland and riparian habitats across Canada, the United States, and northern Mexico.
• Mangrove Yellow Warbler (S. petechia)—the resident southern population that lives year-round in mangroves along the coasts of Mexico, Central America, and northern South America, and on the fringes of Caribbean islands.
Warbling Vireo North America has a major new identification challenge! The long-awaited split of Warbling Vireo has finally arrived: Eastern Warbling Vireo (Vireo gilvus) and Western Warbling Vireo (V. swainsoni). The breeding range splits roughly at the Rocky Mountains and breeding habitats differ, with Western Warbling Vireo occurring in mountain forests—especially riparian forest adjacent to pines—while Eastern Warbling Vireo is a bird of lowland watercourses from the Great Plains eastward, usually in areas with cottonwoods, willows, and other riverside vegetation. The songs differ substantially: listen for Eastern’s more rolling phrases that usually conclude with a rising note at the end, versus Western’s jumpier up-and-down song pattern that usually lacks the strong final rising note.
Whimbrel is another species that occurs on almost all continents. The two-way split into White-rumped Eurasian Whimbrel (Numenius phaeopus) and Brown- rumped Hudsonian Whimbrel (N. hudsonicus) was long predicted and has already been undertaken by some taxonomies. The normal ranges of these two species don’t really overlap, and eBird will automatically assign existing “Whimbrel” reports to a species based on continent: Eurasian Whimbrel in Eurasia; Hudsonian Whimbrel in the Americas. However, a note of caution on vagrants: because these birds are highly migratory, either species can show up on the opposite continent.
“Elegant” no more here... In 2025, Elegant Trogon was split into two species, and the name of the form found in Arizona reverted back to the old name of: Coppery-tailed Trogon, found from Arizona to southern Mexico, and Elegant Trogon, a name now restricted to populations from Guatemala to Costa Rica.
Credit to Team eBird and CLO Taxonomy Team
For a complete list of all taxonomic changes, check out the 2025 eBird Taxonomic Update page.
