Updating the eBird/Clements Checklist 6th Edition

Thomas S. Schulenberg and Marshall J. Iliff
Managers of the eBird/Clements taxonomy

The purpose of the Clements Checklist is to make it as easy as possible for anyone—nonspecialists and professionals alike—to keep track of the ever-changing “master list” of birds of the world. With the last print version published in 2007, we now have moved to providing the eBird/Clements Checklist and its updates entirely online. This allows the list to stay more current and to be used more easily by numerous partners and constituencies. Importantly, the eBird/Clements Checklist forms the backbone taxonomy for eBird—the free online website for tracking your bird lists and sharing your sightings with others, including scientists, conservationists, and educators.

We have several goals in providing regular updates to the eBird/Clements Checklist:

  • to maintain a correct, relevant, clear and current taxonomy to be used by eBird and similar projects
  • to provide downloadable spreadsheet versions to be used by anyone
  • to update the taxonomy annually based on published technical research in peer-reviewed literature and vetted in the avian systematics community
  • to correct any errors introduced by us or persisting from the 6th edition

Whose Taxonomy Do We Follow?

Uniting the taxonomic treatments and philosophies from different regional authorities into a single, cohesive list is no small task. Inevitably, conflicts exist both on specific issues and in general approaches to species limits, English names, scientific names, the sequence of species, genera, and families, and other matters [or “issues”]. At the most fundamental level, we adhere to the Biological Species Concept (BSC), even for allopatric taxa in which the potential for interbreeding can only be inferred by the preponderance of evidence. For the Western Hemisphere, our first authority remains the American Ornithological Society (AOS), which has two committees that publish regular updates: the North American Classification Committee (NACC) covers the taxonomy and nomenclature of North American birds, publishes the official Checklist of North American Birds (AOU 1997), and publishes annual Supplements to this Checklist each September in The Auk; and, for South American birds, we follow the South American Classification Committee (SACC). SACC presents a scholarly treatment of all species occurring south of Panama, and they post their findings (plus literature citations and explanations), as decisions are made, on the SACC website. Usually these two committees agree with each other, with regard to species that occur in both North and South America, but occasionally their taxonomies conflict with each other. In such rare instances, we choose which taxonomy to follow, depending whether the affected species are primarily North or South American. eBird provides a summary of all departures of the most current version of the eBird/Clements Taxonomy from the NACC and SACC).

For birds of the Old World and the oceans, we shall adhere as closely as possible to the taxonomy and nomenclature published by regionally recognized scientific bodies (e.g., British Ornithological Union for European birds, Ornithological Society of New Zealand for New Zealand) and/or regional experts. We also try to minimize departures from other global taxonomies, such as the IOC World Bird List and the Handbook of Birds of the World series (Lynx Edicions, Barcelona). We believe that even when different systems exist, consistency is important where it can be achieved, as that minimizes confusion for birders and data errors within eBird.

Whenever possible we try to use the most current and most correct information, in conjunction with deference to local authorities. For English names we follow prevailing usage, but sometimes adopt novel names to avoid ambiguity. Whenever possible, when a species is split we try to avoid using the same English name and scientific name for the parent and daughter species.

Sequence of Species and Subspecies

Ornithology has entered an extraordinary period of discovery in systematics and taxonomy. Revelations from genetic studies are shifting some of our most familiar bird species into different families and even orders. (One need only study the recent peregrinations of the New World Vultures, Carthartidae, within the AOU taxonomy to get an idea of what lies ahead.) As a result, the sequence of families, genera, and species will be fluid for many years to come.

Subspecies Groups

In December 2009, version 6.5 of the eBird/Clements Checklist adopted the concept of the group, which initially was developed by eBird. A “group” is a distinctive (field identifiable) subspecies or group of subspecies. The group is not a formal taxonomic unit, but often represents a potential future split (and so groups are a valuable taxonomic tool for the savvy birder). Birders that faithfully enter groups in eBird will be rewarded by automatic updates to their lists if and when splits occur.

Some groups are monotypic, that is, they involve only a single subspecies (e.g., “White-winged Junco” Junco hyemalis aikeni), whereas others are polytypic, with two or more subspecies (as in “Oregon Junco,” Junco hyemalis [oreganus Group], which includes seven subspecies of Junco hyemalis). We admit that it sometimes is confusing to refer to a single subspecies as a “group” (!). We now identify all groups as monotypic or polytypic. This allows the user to distinguish easily between the groups that contain multiple subspecies, and those groups that consist only of a single subspecies. The entries identified in the spreadsheet as “subspecies” and as “group (monotypic)” together comprise the entirety of subspecies in the list, whereas the polytypic groups are a secondary level between subspecies and species.

Additional Taxa for the eBird Checklist

eBird’s goal is to collect observations of all birds seen in the field. Therefore eBird maintains a number of categories that are of use for reporting observations from the field, but that are not part of the Clements Checklist. These additional categories—including hybrids, intergrades, slashes, “spuhs,” domestics, and “forms”—generally are added to the eBird taxonomy when a need arises and are reviewed by the eBird team before adding. We welcome recommendations from eBirders on what additional entries in any of these categories would be useful to better record observations in the field.

Updates to Ranges and Status

In some cases, the ranges of species or subspecies are incomplete or inaccurate, or include misspellings or obsolete place names. Since bird ranges are constantly changing and often poorly known, maintaining correct taxonomy and nomenclature are higher priorities than constant tweaks to the range statements. We do continue to accumulate and check all suggested changes in range, however, so please continue to suggest corrections and revisions to our range descriptions.

The eBird/Clements Checklist range statements not include distributional records for vagrants, even those that occur annually (e.g., Pectoral Sandpiper in Europe, Eurasian Wigeon in North America). This means that new North American records of extralimital species (e.g., those published in the 2007 Supplement to the Checklist of North American Birds) are not mentioned in the posted updates. eBird is a great source for range maps (e.g., Barn Swallow, Tropical Kingbird, Australasian Magpie) based on field observations as well as regional species lists (e.g., Chile, Portugal, New South Wales, Australia).

Frequency of Updates and Downloadable Spreadsheet

Official updates and corrections to the eBird/Clements Checklist occur each year in August. Links to previous posts will remain active, so that the eBird/Clements Checklist website will continue to provide the comprehensive list of changes.

Input Welcome, and Thank You!

As always, we welcome and encourage users of the eBird/Clements Checklist to contact us ( subject line “eBird/Clements Checklist”) with any errors or possible errors you encounter. We will do our best to answer your emails directly, although there may be some delay before we do so. As it provides the backbone of eBird and has a large group of longtime users, we are committed to doing our very best to keep this checklist current, up to date, and user-friendly.

We provide sincere thanks to all the individuals and groups that have assisted with the maintenance of this taxonomy over the years. Individuals who contributed assistance are recognized in all annual updates, and are too many to thank here, but we are sincerely grateful to all. Above all others, we wish to thank James F. Clements and the Clements family for entrusting his monumental work to the Cornell Lab of Ornithology; Tom Fredericks, who manages the eBird database and its taxonomy, and provides numerous data quality checks on the published spreadsheet; Denis Lepage, who runs Avibase, and who provides assistance both to the Clements Checklist and to eBird on many taxonomic issues; and Don Roberson who consistently goes above and beyond in his authorship role by providing extensively researched proposals on taxonomy and nomenclature.