New AOU Check-list Changes

The 53rd Supplement to the American Ornithologists’ Union Check-list of North American Birds was published this week, with an extensive array of taxonomic changes including a split of the Xantus’s Murrelet and dramatic rearrangements of falcons and parrots to new positions on the list. By stipulation, the ABA adheres to AOU classification and nomenclature, so we can expect these changes to be made in the ABA Checklist as well.

The bird known until now as Xantus's Murrelet (photo at left from wikipedia) has been split in two. Its former scrippsi and hypoleucus subspecies have been elevated by the AOU to full-species status. The new species are Scripps’s Murrelet (Synthliboramphus scrippsi) and Guadalupe Murrelet (S. hypoleucus). Scripps's breeds on islands off southern California and western Baja California. Guadaulpe breeds on Guadalupe Island and other islands off western Baja—and wanders at least casually north into U.S. waters after the breeding season. The split is based on a combination of factors: lack of evidence of interbreeding where the two taxa are sympatric, and differences in morphology (especially facial pattern and bill shape), vocalizations, and genetics.  

Falcons and parrots are moved far away from their long-standing placements in the official taxonomic sequence. Recent genetic studies found that falcons are much more closely related to songbirds than to other “hawks”—quite a jolt to our traditional belief. According to this research, falcons' closest relatives are a group (or "clade") consisting of the parrots and the passerines. As a result, the new Check-list sequence inserts Falconiformes (caracaras and falcons) and Psittaciformes (parrots) between Piciformes (woodpeckers) and Passeriformes (songbirds). These major revisions show us once again that as scientific knowledge improves, long-standing taxonomic sequences are not sacrosanct.

There are two other splits, which don’t add or subtract ABA Area species:

• Gray Hawk is divided into Gray Hawk (newly named Buteo plagiatus), which is resident from southern Arizona, New Mexico, and Texas south through Middle America; and Gray-lined Hawk (B. nitidus), which is resident from Costa Rica south through much of South America.

• Galapagos Shearwater (Puffinus subalaris) is classified as a species separate from Audubon’s Shearwater.

A number of ABA Area genera are altered, based on genetic research:

• Chuck-will’s-widow, Buff-collared Nightjar, Eastern Whip-poor-will, and Mexican Whip-poor-will   are moved from Caprimulgus back to Antrostomus, their genus until the 19th Supplement to the AOU Check-list in 1944. Old World nightjars remain in Caprimulgus.

• Calliope Hummingbird joins Broad-tailed, Rufous, and Allen’s hummingbirds in the genus Selasphorus.

• Sage Sparrow moves from Amphispiza to its own newly named genus Artemisiospiza (which combines the Latin generic name for sage, Artemisia, with the Greek word for finch, spiza).

• Purple Finch, Cassin’s Finch, and House Finch were formerly in the genus Carpodacus along with Eurasian rosefinches, including the Common Rosefinch, but are now placed separately in Haemorhous, the resurrected name of an old finch genus.

Many other taxonomic changes are adopted for Mexican, Middle American, and South American species, and birders interested in those regions will want to learn about them as well. The Supplement is 16 pages long, and anyone deeply interested in Western Hemisphere avifauna will find it worth taking a lot of time to study.

The new Supplement will be covered further in articles by Michael L. P. Retter and Peter Pyle in the September 2012 issue of Birding, including an associated Michael-and-Peter "conversation" online. The ABA Checklist Committee will provide further interpretation in its annual report in the December 2012 Birding.