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Breaking Up the Hawks

Nine years since we were surprised to see loons and grebes moved down past waterfowl, grouse, and quail on our checklists, we might soon see an even more dramatic revision. Falcons could be uprooted from their traditional place just after other “hawks” and moved far down the list almost to songbirds.

This prospect faces the American Ornithologists’ Union Committee on Classification and Nomenclature of North and Middle American Birds (the “Check-list Committee”) after it recently received a formal proposal for the change. The AOU’s South American Classification Committee unanimously approved the rearrangement in January.

If the North and Middle American panel adds its approval, we should probably realize that it was only a matter of time. Since 2006, three different studies have demonstrated that falcons are much more closely related genetically to parrots and passerines than they are to other raptors.

One of the studies was reported in Birding in January 2009, illustrated by a cladogram, the evolutionary “family tree,” shown below. The branches represent clades—independent but interrelated lineages that diverged from a single ancestor. At the top is a clade that includes falcons (Order Falconiformes), parrots (Order Psittaciformes), and passerines (Order Passeriformes). These three are more closely related to one another than to all other orders.

Cladogram for Hawks blog post
Sequences of taxa represent evolutionary relationships, and the proposed new sequence would begin after the Piciformes (woodpeckers). Starting with woodpeckers, the  sequence would be Piciformes, Falconiformes, Psittaciformes, and Passeriformes. Dismaying as this—or any—major rearrangement of our checklists may be, we have to keep in mind that it reflects a refinement in our understanding of avian evolutionary history.

Details about that and other newly recommended AOU Check-list revisions are available in the AOU committee’s online compilation of pending proposals. Most involve species occurring in North America, although the other recommendations are less drastic than the transfer of the Falconiformes. Here are four of the proposals, three taxonomic and one geographic:

• Reinstate the Yellow-eyed Junco subspecies bairdi in Baja California Sur to full-species status as Baird’s Junco based on song, morphology, and disjunct range from other subspecies. An error in the proposal refers to a 2011 paper by Nathan D. Pieplow and Clinton D. Francis, who describe distinctive vocal characteristics of bairdi. The proposal states that Pieplow and Francis suggested species status. They did not. Rather, they called for genetic studies well as field work to determine whether there is a barrier to interbreeding with other subspecies.

• Revise the sequence of Spizella sparrows to reflect recent genetic research. The new sequence would be American Tree, Chipping, Clay-colored, Black-chinned, Field, Worthen’s, and Brewer’s. This would break up the time-honored trio of Chipping, Clay-colored, and Brewer’s, which have been together in that sequence since the first edition of the AOU Check-list in 1886. 

• Move New World goatsuckers now classified in the genus Caprimulgus, including Chuck-will’s-widow, Buff-collared Nightjar, Eastern Whip-poor-will, and Mexican Whip-poor-will, into a long-defunct genus Antrostomus. Our familiar Caprimulgus genus would be maintained only for Old World goatsuckers—one of which, the Gray Nightjar (formerly the Jungle Nightjar), is on the AOU and ABA lists based on a 1977 specimen from the Aleutian Islands.

• Add European Golden-Plover to the AOU’s United States list, based on records from Alaska, Delaware, and Maine. (The ABA Checklist already includes the 2001 Alaska record.)

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