For those who keep life lists, the 2023 bird taxonomy update has just been announced. 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. 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 Clements Checklist of Birds of the World, or Clements Checklist for short. The Clements Checklist is updated annually to reflect the latest developments in avian taxonomy.
In the US, there are 2 notable “splits” and one notable “lump”.
- Northern Goshawk is split into Eurasian Goshawk (Accipiter gentilis) and American Goshawk (Accipiter atrocapillus)
- Cattle Egret is split into eastern and western populations (the western birds are the ones that colonized the Americas), so birders should get used to Western Cattle Egret (Bubulcus ibis) and Eastern Cattle Egret (Bubulcus coromandus)
- Pacific-slope Flycatcher (Empidonax difficilis) and Cordilleran Flycatcher (Empidonax occidentalis) are being lumped–once again–as Western Flycatcher (Empidonax difficilis). These flycatchers were last considered a single species in 1989. The earlier decision to split is being reversed following new evidence of extensive interbreeding. The reclassification comes as a relief to many birders, given the previous difficulty of telling these two species apart in the field.