Welcome back Western Flycatcher!
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
We present excerpts from the annual report on changes to the North American Checklist of Birds from the American Ornithological Society.
The American Ornithological Society’s (AOS) Committee on Classification and Nomenclature of North and Middle American Birds (a.k.a. NACC) has re-lumped Pacific-slope and Cordilleran Flycatchers into the species named Western Flycatcher. This is a change that was anticipated based on new information and welcomed by many birders, including this writer, who were unable to tell the two flycatchers apart. In fact, they were so close in identification that the two continued to be included in what was called the “Western Flycatcher Complex.” This change is the most important in bird taxonomy in the 2023 Supplement to the American Ornithological Society’s checklist of birds. Some other changes in Middle American birds are also summarized below.
LUMP OF THE WESTERN FLYCATCHER
This split of the Western Flycatcher was made in 1989 on the basis of a few pairs of mating birds and some differences in the dawn song and male position notes of the birds studied. At that time this was enough evidence for the NACC to agree to split the Western Flycatcher into the Pacific-slope Flycatcher thought to reside on the western slopes of mountain ranges from British Columbia, the Cascades, and Sierra Nevada. The Cordilleran Flycatcher was assigned the eastern slopes of these ranges and the mountains of the Southwestern United States and Mexico. However, more recent genetic research of the birds has determined that the same genetic information is found in a wider group of members of both the Pacific-slope Flycatchers and Cordilleran Flycatchers.
To state the argument for lumping briefly without excessive technical language, the two flycatchers are so much alike that they meet the criteria for neither the Biological Species Concept, which requires reproductive isolation, nor the Phylogenic Species Concept, which requires separation based on differences in appearance and vocalizations. The genetic evidence showed significant interbreeding, and the analyses of birds in the hand and through spectrograms of vocalizations found insufficient differences between the two species. They were so similar that they could not be identified by sight, and the vocalizations among birds in both species varied to such a degree that many birds cannot be assigned exclusively to either species.
eBird will soon make these changes and will assign all formerly identified Pacific-slope and Cordilleran Flycatchers to Western Flycatcher which will now be the only choice in eBird for these flycatchers. Sorry, for those of us who have both species on our life list. We will lose one tick off our list with this change.
SPLIT OF THE NORTHERN GOSHAWK
This split of this goshawk reverses a lump made in 1957 and assigns new common names to the two separate species. Recent analysis has found that the Eurasian Goshawk, which retains the scientific name Accipiter gentilis, is more closely related to other Eurasian species than it is to the newly named American Goshawk (Accipiter atricapillus). There are significant genetic and vocal differences between the two species. If you have already seen what is now a Eurasian Goshawk in Europe, Asia, or an accidental sighting in North America, you will be able to add a tick to your life list with this change.
FIVE SPLITS IN CARIBBEAN BIRDS
As part of an effort among the AOS’s North and South classification committees and the Working Group on Avian Checklists to consolidate the four main global checklists into a single standardized checklist, the committee has recognized that some Caribbean birds need reclassification and they have made the following four changes this year. There will be more changes as this project continues.
Cuban Bullfinch Species Split
The Cuban Bullfinch (Melopyrrha nigra), a finch-like tanager, is being split into two species, Cuban Bullfinch (M. nigra), now restricted to Cuba, and Grand Cayman Bullfinch (M. taylori). The NACC passed a proposal submitted by NACC members Jonathan Dunn and Terry Chesser to split the bullfinch after re-evaluating evidence showing song and morphological differences.
Greater Antillean Nightjar Species Split
The Greater Antillean Nightjar (Antrostomus cubanensis) is being split into two species based on vocal differences. A proposal submitted by NACC members Dunn, Chesser, and Carla Cicero summarized the convincing differences between what will now be the Cuban Nightjar (A. cubanensis) and the Hispaniolan Nightjar (A. ekmani).
Three-way Split for Antillean Euphonia
The Antillean Euphonia (Chlorophonia musica) is a small, attractive woodland finch found on many Caribbean islands. This species formerly consisted of three subspecies that will now be considered separate species. Researchers recommended the split based largely on plumage differences on a par with those between other species of euphonia; the three species will now be the Hispaniolan Euphonia (C. flavifrons), Puerto Rican Euphonia (C. sclateri), and Lesser Antillean Euphonia (C. musica).
Palm Crow Species Split
The Palm Crow (Corvus palmarum), a corvid long shared between Hispaniola and Cuba, will now be treated as two species: the Hispaniolan Palm Crow (C. palmarum) and the Cuban Palm Crow (C. minutus). NACC member Pamela C. Rasmussen based her proposal primarily on differences in vocalizations, genetic evidence, and apparent differences in tail-flicking behavior.
This writer is grateful for information for this article taken directly from the AOS 64th Supplement to the Check-list of North American Birds published in Ornithology, July 6, 2023.