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AOU Committee on Classification and Nomenclature of North and Middle American Birds

The AOU Committee on Classification and Nomenclature of North and Middle American Birds ("North American Classification Committee," NACC) is an official committee of the American Ornithologists' Union whose mission is to keep abreast of the systematics and distribution of North and Middle American birds, with the purpose of creating a standard classification and nomenclature. The NACC produces editions of the Check-list of North American Birds, as well as annual supplements to the latest edition (published in the The Auk: Ornithological Advances). This classification is subject to revision as new data are incorporated.

AOU Checklist: 7th Edition and Supplements

Access the Checklist Online »

Access and Download the Complete Check-list of North American Birds, 7th edition and its supplements »

Committee Members

R. Terry Chesser (Chair), Kevin Burns, Carla Cicero (co-Chair), Jon L. Dunn, Andrew W. Kratter, Irby J. Lovette, Pamela C. Rasmussen, J. V. Remsen, Jr., James D. Rising, Douglas F. Stotz, Kevin Winker.

Student Systematics Group: Nick Mason, Dave Slager.

Technical Advisors: David Bridge, Normand David, Phil Davis, Daniel D. Gibson, Michel Gosselin, Dan Haig, Michael A. Patten.

General Philosophy

The NACC operates under the philosophy and procedures outlined in the Preface to the 7th edition. Although the committee recognizes the controversy over species concepts in ornithology, it generally adheres to the principles of the Biological Species Concept. Multiple lines of evidence (e.g., multiple genetic loci, or genes plus other traits) are favored over single data sets for taxonomic changes at species and higher levels. The committee prefers to act conservatively in its treatments of taxonomy and nomenclature; thus, proposals that suggest but do not strongly support taxonomic change, or that cause instability, may be rejected pending further data. We generally require at least two independent datasets for making changes at higher-level classifications.


The NACC operates on a proposal basis. Proposals are submitted and reviewed for taxonomic changes, English name changes, acceptance of distributional records, and other items related to the charge of the committee. Members of the committee as well as non-members may submit proposals following the committee's Proposal Guidelines. Proposals are submitted to the Chair of the committee, and sets of proposals are distributed periodically (2-5 times per year) to the committee for discussion and voting. Proposals must receive a 2/3 favorable vote to pass. Proposals that do not pass may be resubmitted at a later date if additional data are published in favor of the proposal. In documenting species' distribution, the Committee generally defers to state committees and to the American Birding Association for acceptance of records.

Current NACC Proposals »
Prior NACC Proposals »
Guidelines for Submitting a Proposal »

English Names

The Committee's policy on English names is stated in the Foreword to the 6th (1983) edition of the Check-list of North American Birds (pages xxi-xxiii), and is further elaborated in The Auk 124:1472, 2007. Additional comments on English names and the controversy over hyphenation of compound names can be found here:

Spelling rules - IOC World Bird List »
Use of hyphens in group bird name - South American Classification Committee »
On hyphens and phylogeny - WJO 2009 »


The last edition of the AOU Check-list to include subspecies was published in 1957 (5th edition). For reasons of expediency, the Committee reluctantly excluded treatment of subspecies in both the 6th and 7th editions, although it continues to endorse the biological reality and practical utility of subspecies as a taxonomic rank. Subspecies that reflect biological diversity play an important role in flagging the attention of evolutionary, behavioral, ecological, and conservation biologists. After careful study, an unknown number of subspecies likely will unmask cryptic biological species, or "species-in-the-making" that constitute a significant element of newly evolving biodiversity. On the other hand, the Committee also recognizes that an uncertain number of current subspecies apply to poorly differentiated populations and thus cannot be validated by rigorous modern techniques.

Although a complete revision of North American avian subspecies has not been done, we refer readers to Avibase and the Birds of North America Online for more up-to-date treatments of subspecies. The Birds of North America project is systematically revising subspecies account for North American birds (see list of accounts revised to date »).

Check-lists of Other Regions

AOU South American Classification Committee »
British Ornithologists' Union »

Other Links

Assembling the Tree of Life: Early Bird »
Avian Tree of Life (Modern Birds) »
History of North American Bird Names »

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