On the ornithological community rejoiced on August 15, 2025 when the 66 th Supplement to the Check-list of North American Birds was released. This recently released update added major upgrades in bird classification and identification. Published in the esteemed journal Ornithology, this comprehensive document, authored by R. Terry Chesser and his colleagues, presents crucial taxonomic revisions and the recognition of new species that will impact both birdwatchers and researchers alike.
Among the notable changes, two new species have been identified: G. candida, known as the Blue-billed White-Tern, and G. microrhyncha, or the Little White-Tern. We look forward to hearing more about how these birds have been recently separated from the formerly known G. alba, the Atlantic White-Tern. This marked reassessment is a continuation of an ecologist’s long-term project to update avian taxonomies based on new DNA evidence.
Significant Taxonomic Changes
The Supplement makes one of the clearest and most important to recent ornithological molecular phylogenetic family rearrangements adjustments – with respect to 12 families of birds. Specifically, the genera Gygis, which includes white-terns, and Anous, known for noddies, have been assigned their own distinct subfamilies: Gyginae and Anoinae, respectively. This new sequence represents a leap forward in our understanding of the evolutionary relationships between these species.
Secondly, the Nutting’s Flycatcher complex had recently been reviewed critically. The complex now includes several additional subspecies, such as M. n. inquietus, M. n. nuttingi, and M. n. flavidior. Taxonomic status Myiarchus flavidior has been treated as a distinct species. Now it’s the Salvadoran Flycatcher too! This distinction is important because it draws attention to the unique characteristics that exist within flycatcher species that might have otherwise gone unnoticed.
The taxonomy of raptors has undergone some major changes. Molecular evidence concludes that harriers are more related to species within the genus Astur. They are more distantly connected than those in Accipiter. As a result of these studies, the genera Accipiter and Astur have been reevaluated and reorganized according to these results.
Reorganization of Raptors
The implications of these discoveries on the raptors that have already been transformed our understanding of their family relationships. The Supplement also sheds light on the question of whether hawks in the genus Accipiter constitute a monophyletic group. This discovery indicates a more complicated evolutionary story than we were aware of before. That analysis results in a significant taxonomic change, as Cooper’s Hawk (A. cooperii) is now placed in the genus Astur. In contrast, the Sharp-shinned Hawk (A. striatus) remains a resident member in the Accipiter clan.
This long awaited reorganization deepens our understanding of raptor evolution and will certainly help ornithologists more easily identify these birds in the field. By improving existing classifications with genetic data, researchers can direct their conservation efforts more strategically and effectively.
Splitting of Species and New Family Classifications
Vireo gilvus, commonly known as the Warbling Vireo, has been split into two distinct species: Vireo swainsoni (Western Warbling-Vireo) and V. gilvus (Eastern Warbling-Vireo). This modification to their taxonomic understanding permits a much better understanding of their geographic ranges and ecological requirements.
Additionally, the family Phaenicophilidae has been redefined the Greater Antillean Tanagers and now consists of two subfamilies and nine species. This tanager reclassification mirrors the continued research into the phylogenetics between these tanager species and their expansion throughout the Greater Antillean archipelago.
