Clements Checklist

Overview: December 2009

Go directly to the updates & corrections

This is the fourth installment of updates and corrections to the sixth edition of The Clements Checklist of Birds of the World. Our updates and corrections continue to be referenced to the relevant page number in the sixth edition, although with each year the Clements Checklist diverges more and more from the sequence of species found in the last print edition. Also note that in some cases, the correction is to last year’s spreadsheet (Clements Checklist 6.3.2), and not necessarily to the sixth edition itself. As before, the entire checklist (including the 2009 updates and corrections), is available as a downloadable spreadsheet (in Excel); this year’s spreadsheet version is Clements 6.4. The spreadsheet contains 10 fields (data columns); the new columns are marked with an asterisk:

Sort 6.4  * reflecting the arrangement of species in this edition of Clements Checklist

Sort 6.32  reflecting the arrangement of species in last year’s edition of Clements Checklist

Page 6.0 reflecting the position of the species in the last print edition

Category reflecting whether the entry on that line is a species, a subspecies, or a group

Extinct * a dagger (†) in this column means that the species or subspecies is extinct

Scientific name

English name




As before, we make corrections to minor mistakes, such as spelling errors or other typographic mistakes. We add one new recently described species, and also add several recently described or previously overlooked subspecies. As before, we update the taxonomy and nomenclature of species for North and South America, based on decisions of the North American Checklist Committee, or NACC, and of the South American Classification Committee, otherwise known as SACC. This year we also follow suit for much of Europe, based on the British Ornithologists’ Union Records Committee, or BOURC. For New Zealand and associated islands, we follow the the Checklist Committee of the Ornithological Society of New Zealand (OSNZ). The fourth edition of the OSNZ Checklist, on which our decisions were made, is in press. These regional authorities do not always agree amongst themselves, of course, so where necessary the final decisions on taxonomy and nomenclature are made by the Clements Checklist team. In future updates we will add additional regional authorities to our roster of baseline sources.

Most of our effort with regard to the 2009 Updates and Corrections was devoted to an overhaul of the classification of birds at the level of the family, especially among the oscine passerines. Studies based on DNA hybridization suggested years ago that the then-current classification of birds was incorrect in many ways. One problem was that some families contained a mixture of species that were shown not to be related to one another. The Clements Checklist responded at the time to these discoveries by recognizing a series of new bird families, such as the cisticolas and allies (Cisticolidae) and the monarch flycatchers (Monarchidae). Not surprisingly, further research — now primarily based on DNA sequences — has confirmed the earlier results and in many cases extended them, so that we now have yet more families to recognize, and we continue to shuffle genera from one family to another. As a result of the 2009 Updates and Corrections, the Clements Checklist loses 6 families, but gains no fewer than 20 new or reinstated families. The total number of families currently recognized by Clements Checklist stands at 221.

Another problem, again stemming originally from the DNA hybridization research but now confirmed with DNA sequence data, is that the relationships between many families turned out to much different than had been thought. This problem had not been addressed by Clements Checklist, at least not in a systematic way, until now: to better reflect our current understanding of the relationships between families, the sequence in which the families are listed is revised considerably in this year’s undates. Please consult the Updates and Corrections for additional details.

We also continue to expand our coverage of “groups,” a new feature for Clements Checklist that we introduced last year. We do not document new groups in the Updates and Corrections pages; to find the groups, you will have to consult the downloadable spreadsheet. (But, if our treatment of an existing group is revised, then we do document the changes.) The template for the group concepts is the eBird taxonomy, which is used for eBird, the online checklist management system. To recapitulate, the group is a distinctive (field identifiable) subspecies or group of subspecies. The group is not a formal taxonomic unit; but, properly understood, the group is a valuable taxonomic tool for the birder.

To understand the group concept, think of a familiar species such as the Red-winged Blackbird Agelaius phoeniceus. This is a very wide-ranging species, with no fewer than 24 subspecies recognized in Clements Checklist. But, not all subspecies are created equal. Most of the subspecies of Red-winged Blackbird can be identified, if at all, only in the hand by subtle differences in size; most are indistinguishable in the field. Indeed, limited experimental data suggest that the size differences owe as much or more to environmental effects than they do to genetics; in other words, some subspecies not only are difficult to distinguish, but have very little biological basis. By comparison, a few subspecies are strikingly different, as different in appearance, or nearly, as different species. A set of four subspecies in California, the Bicolored group, for example, are readily identifiable: the male lacks the yellow margin to the red “shoulders,” the female is more darkly colored than other female Red-winged Blackbirds, and so on. A similar, but geographically isolated, subspecies is found in central Mexico. So we can arrange the 24 subspecies of Red-winged Blackbirds into three groups:

Red-winged Blackbird (Red-winged), with 19 subspecies;
Red-winged Blackbird (California Bicolored), with four subspecies; and
Red-winged Blackbird (Mexican Bicolored), with one subspecies.

Doing so helps us organize 24 subspecies into a smaller set of units, and also conveys information that is useful to the birder in the field.

The group concept has other values. Often a unit that we identify as a group is a distinctive subspecies or set of subspecies that are prime candidates for a future split. The arrangement of the 19 subspecies of Fox Sparrow Passerellus iliaca into four groups is a good example of this. We don’t know when this will happen, but we are certain that it is just a matter of time before the Fox Sparrow is split into three or (more likely) four full species. Each of these potential species is identified in Clements Checklist as a group. It’s better to start now to track your sighting of Fox Sparrow by group, so that when the split does come, you’ll know which species you’ve seen! Becoming comfortable with the group concept can add more joy to your birding, and make future life list revisions a lot easier.

There are two other structural changes this year to the Clements Checklist. In last year’s spreadsheet, a dagger (†) was placed after the name of an extinct species or subspecies. This makes it more difficult to properly sort names in the spreadsheet. Therefore, this year we remove the symbol from the name of the species or subspecies, and place the dagger in a separate column.

This year we also eliminate the subspecies synonymies — that is, the list of “alternative” names in parentheses that often appeared in the Clements Checklist (for example, Turnix maculosus melanotus (yorki, pseutes) for Red-backed Buttonquail Turnix maculosus melanotus. In practice, there often are synonyms not only for subspecies names, but also for species names, genus names, family names, and so on. There is little rationale for providing synonyms for names only at the subspecies level, but not for the other categories. Also, the synonym itself does not help the user decide which name is valid; other information is necessary, such as the author of each name and the date of publication. There is a specialized literature that often provides the information needed to sort through a synonymy. In the past, this literature typically was available only in major research libraries, but now important reference works, such as the multi-volume series of the Catalogue of the birds in the British Museum, of the Catalogue of birds of the Americas, and of Peters Check-list of birds of the world, all can be found online (e.g, via Therefore we no longer see a justification for giving the list of subspecies synonymies, and so these alternative names are removed from Clements Checklist.

Here are some final summary statistics:
number of families:       221
number of taxa:           31573
number of species:     9995
number of unique subspecies: 21107
number of groups:     1235 (with more to come!)

Please continue to report potential errors and corrections to Clements Checklist. We are well aware that we still have a large backlog of errors and corrections to process. We are making slow — slow but steady — progress on these revisions, and we think we might even get caught up some day (!). Many of the errors that you find are ones that we would have taken a long time to notice, so we appreciate your help and we do want to hear from you.

We thank Tom Fredericks for his assistance with the Excel spreadsheet. Shawn Billerman provided the baseline for our oscine passerine revisions, and was a useful sounding board for discussions on the subject. Michel Gosselin provided sound advice on some details of nomenclature; we appreciate his assistance, and we also take full responsibility for any errors on this front. Denis Lepage, who runs Avibase, has pointed out errors and helped with many taxonomic issues through this process; we anticipate the linkages that Denis creates to be very helpful for the future of the Clements list. We also thank the following for their help in pointing out errors in Clements or directing us to important literature for our consideration:

Chuck Almdale, Nick Baker, Geoff Barlow, Jerry Blinn, Nick Block, Ted Buerger, Ken Burton, Claes-Göran Cederlund, Paul Clapham, Elaine Couling, Andy Cubbon, Theo de Kok, Stijn De Win, Wendy Ealding, Stefan Ericsson, Roger Evans, Kieran Fahy, Rob Felix, Shawneen Finnegan, Frank Gill, Mike Green, Dale Herter, Brian Hillcoat, Andrew Howe, Vernon Howe, Ron Johns, Paul Johnson, Rex D. Kenner, Markus Lagerqvist, Niels Larsen, Jack Levene, Glenn Mahler, Bill Maynard, Karen McBride, Matthew Medler, Andy Musgrove, Michael Nielsen, Adrian Nye, Steve Olesen, Cathy Pasterczyk, Brian Penney, Shaun Peters, Paul Radley, Colin Richardson, Peter Roberts, Holger Schritt, Roger Staples, Ed Stonick, Phil Tizzard, Gordon Tufts, Peter Vercruijsse, James Yurchenco, and no doubt others whose names we have overlooked but who made suggestions and proposed corrections to the Clements Checklist.

Thanks to all for your support, and we look forward to your feedback.

Thomas S. Schulenberg (Avian Taxonomist), and Marshall J. Iliff, Brian L. Sullivan, and Christopher L. Wood (eBird Project Leaders)