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Bulletin: New Splits

The American Ornithologists’ Union “Check-list Committee” has published an online preview of its decisions on dozens of taxonomic and nomenclatorial proposals that will take effect this year if there are no last-minute revisions.

The report includes splits of four species involving ABA-area birds, but none of them adds a species to the ABA Checklist. That’s because each divides a species already on the ABA Checklist from one outside the ABA area. Three other proposals would have added new ABA-area species, but those failed to gain approval.

Here are the splits that passed:

• Common Moorhen returns to its former name Common Gallinule (Gallinula galeata) in the New World as a separate species from Moorhen (G. chloropus) in the Old World. This vote passed unanimously, although one member believed the new name for “our” bird should be American Gallinule. A bird thought to be a vagrant from the Old World was photographed and collected on Shemya Island, Alaska, in October 2010. If accepted as a Moorhen, it would be the first ABA-area record.

Snowy Plover • Snowy Plover becomes Snowy Plover (Charadrius nivosus) in the New World and Kentish Plover (C. alexandrinus) in the Old World. The vote was 8–3, with the majority favoring the split because of genetic divergence and other differences between the two former subspecies. An interesting situation in Alaska arises in this case as well. Alaska’s only Snowy Plover record, photographed at the Nome River mouth in 1991, will now need to be reexamined to determine whether it can be identified as a Snowy or a Kentish.

 

• Bahama Warbler (Dendroica flavescens), a Bahamian endemic, is recognized as a distinct species from Yellow-throated Warbler, which will retain the name Dendroica dominica. The 8–3 vote was marked by disagreement over whether distinctions in mitochondrial DNA, plumage, and vocalizations were sufficient to warrant species status.

• Mexican Jay becomes two species, Mexican Jay (Aphelocoma wollweberi), which reaches its northern range limit in Arizona and southern New Mexico, and Transvolcanic Jay (A. ultramarina) in Mexico. The split was favored 9–2 based on differences in genetic structure, plumage, vocalizations, and measurements.

Here are the proposed splits that failed:

• Return of Mexican Duck (Anas diazi) to species status separate from Mallard. This vote was close: 5 in favor, 6 against. The dissenters felt that the degree of hybridization between the two has not been established and that phenotypic differences are inconclusive.

• Split of Mountain Chickadee into a Rocky Mountain–Great Basin species and a Pacific-region species resident in the Sierra Nevada and Cascades. The vote was 9–2 against separating them. Among various reasons, the majority felt that there was insufficient evidence of reproductive isolation between the two.

Audubon's Yellow-rumped Warbler • Split of Yellow-rumped Warbler into two, three, or four species. The present subspecies, “Myrtle” group (coronata), “Audubon’s” group (auduboni), “Black-fronted” (nigrifrons), and “Goldman’s” (goldmani) are all part of the picture. A split of Myrtle and Audubon’s, of course, would have added an ABA Checklist species. Black-fronted is a resident in Mexico, and Goldman’s occurs only in southernmost Mexico and Guatemala. Neither of those two has been recorded in the ABA area. The vote was 7–4 against any divisions of the Yellow-rumped complex until further genetic analysis and determination of the extent of interbreeding in the subspecies’ contact zones.

Taxonomically, the most far-reaching proposal accepted by the committee is an extensive rearrangement of wood-warbler genera in the family Parulidae. The new arrangement, adopted by an 8–2 vote with one abstention, will move many species into new genera and will end the venerable genus Dendroica. (Birds in that genus, whose Latin name nicely  means “tree-dwelling,” will now become part of the genus Setophaga, whose name means “moth-eating.” Ugh!—but that stems from standard rules of scientific nomenclature.

The parulid proposal was covered extensively in an article in the March 2011 issue of Birding and a WebExtra to that issue. The status of Yellow-breasted Chat is not clear to me. The proposal to the AOU intentionally did not include the chat in the Parulidae because recent studies have strengthened the view that it is not a wood-warbler. So, a question arises: Does the AOU vote automatically separate the chat from the Parulidae without fanfare, or was this subject not addressed explicitly because it wasn’t part of the particular generic rearrangements proposed?

All proposals and votes by the AOU panel—formally named the Committee on Classification and Nomenclature (North and Middle America)—are subject to change pending further data or discussion. The outcome of these proposals is not final until publication of the annual supplement to the Check-list of North American Birds in the July 2011 issue of AOU’s journal The Auk. Rarely, however, do any such last-minute changes occur.

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