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The History of North American Bird Names
in the
American Ornithologists' Union Checklists
1886 - 2000

The A.O.U.

The American Ornithologists' Union was organized in 1883 and published its first listing of the birds of North America in 1886. There have been six subsequent editions of the Checklist which appeared in 1895, 1910, 1931, 1957, 1983 and 1998. Interim supplements to the published editions appear about every two years in the AOU's journal, The Auk. Data from the seven editions as well as from the supplement of 2000 appear here.

The original boundaries of the AOU Checklist area of coverage included all of North America north of Mexico, as well as Baja California, Bermuda and Greenland. The webpages of this website report only on the species attributed to this original area of coverage.

In the Sixth Edition of 1983 the Checklist area was enlarged and modified. Greenland was dropped, while the Hawaiian Islands, West Indies, and Central America south through Panama were added. This more than doubled the number of species contained in the Checklist.

The purpose of this website is to permit the birdwatcher or student of ornithology to gain some insight as to how and (approximately) when the names of birds (taxonomic and vernacular) have changed over time. I say "approximately" because, for example, a change of name in the 7th Edition of 1998 might have become official in a supplement of 1987-88. At some later time I might add to the Notes column of the species listings the actual year that changes were published.

AOU Checklists are prepared by the organization's Committee on Classification and Nomenclature. Committees are usually composed of 8-10 ornithologists and/or taxonomists with extensive experience within their professions. You might recognize a number of the names of Committee Members who worked on the Checklists over the years.

For the AOU Checklist Area covered here the main species list has grown from 768 in 1886 to 929 species today. Many people assume this growth in species has come about by "splitting" a listed species into two or more species. In fact the record shows that 121 species have been downgraded or "lumped" while 45 have been elevated or split, for a net loss of 76 species. I should point out that some species have been split/lumped multiple times.

Species on Current Checklist
Lump/SplitPacific Loon
Lump/SplitRock Sandpiper
Lump/SplitLong-billed Dowitcher
Lump/SplitYellow-legged Gull
Lump/SplitGilded Flicker
Lump/SplitRed-breasted Sapsucker
Lump/SplitFlorida Scrub-Jay
Lump/SplitIsland Scrub-Jay
Lump/SplitNorthwestern Crow
Lump/SplitYellow-green Vireo
Lump/SplitBullock's Oriole
Lump/SplitBoat-tailed Grackle
Lump/SplitBlack Rosy Finch
Lump/SplitBrown-capped Rosy Finch
Lump/SplitSpotted Towhee
Split/Lump/SplitCalifornia Towhee
Split/Lump/SplitNelson's Sharp-tailed Sparrow
Forms Once Considered Species
Lump/Split/LumpHarlan's Hawk
Lump/Split/LumpBlack-eared Bushtit
Lump/Split/LumpGray-headed Junco
Lump/Split/LumpBaird's Junco
Split/LumpRodgers's Fulmar
Split/LumpSage (Bell's) Sparrow
Split/LumpPink-sided Junco

In the this table are listed those species that have undergone multiple splitting and lumping. Some of them have been affected by as many as three taxonomic decisions.

Although not shown here, the Herring Gull has been involved in splitting or lumping in five of the six Checklist editions subsequent to the first edition. The Bushtit was affected by changes in four editions.

In a number of these cases, as well as in many instances involving vernacular name changes, one gets the distinct impression that the Committee for one Checklist edition expressed their displeasure with changes wrought by the previous Committee.

The Juncos and Gulls were the groups that underwent the greatest number of lumps/splits over the years.

The Sage Sparrow is, of course, on the current checklist. The vernacular name was transferred to what had been known as Bell's Sparrow.

Change in Species Totals Between Checklist Editions

The table below provides a summary of Committee decisions reflected in each edition of the checklist. Changes in the supplement of 2000 are included in the 1998 column. There have been 1072 species or forms on the checklist at one time or another since 1886. Of these, 225 forms have been the subject of lumping or splitting actions. A substantial increase in species, reflecting the completion of exploration of the continent, is shown in 1895. For more than 60 years afterward the species count remained stable, in fact, shrinking by three. New species being added were offset by lumpings and those removed to the hypothetical list (appendix).

Actions Taken
Beginning Species Count0768799802802796848768
A.  Placed on Appendix or Dropped  (A) -1-12-11-10-16-7-57
B.  Number of Species Merged/Lumped  (L) -7-22-38-24-300-121
C.  Number of Species Split/Elevated  (S) 065482245
D.  Species Added for First Time 393044248264283
E.  Species Retrieved from Appendix 01008211
Net Change in Species Listed 3130-65281161
Ending Species Count768799802802796848929929

The combined numbers for the 1983 and 1998 (2000) editions, spanning 43 years of Checklist activity are interesting. Lumps equaled splits in this period (but note the imbalance in 1998). There was a net loss of 13 species to the appendix. But 146 new species were added, more than during the preceding 71 years. I think this must be attributed to the massive increase of amateur and professional observers in the field as well, perhaps, to the acceptance of photographic evidence to substantiate sight records. The popularity of pelagic birding trips has contributed records from offshore waters.

Some splitting of species based upon modern genetic studies has already been done. I predict that there will be substantial future growth in species based upon this relatively new form of evidence.

Accidental and Casual Species

The Checklist notes species which are accidental in or range casually to the checklist area. These are noted in the table below, where they are grouped according to region. Increased observation in the western Aleutians and mainland Alaska, as well as along the Pacific coast, have contributed more than one-third of these additions to the Checklist.

Species ranging over the Mexican border provide the second largest group of new birds. Some of these are regular breeders or visitors, but restricted to a narrow band within our border states. Accidentals from Europe (East Coast) rank below those derived from the West Indies (Florida and Gulf states). A few Euro-Asian species have been found widely scattered across North America.

Thus, of 283 species added to the Checklist since 1886, 209 fall within categories shown in this table.

Species1886Recorded Since 1886Notes
AC Alaska731063  
AC West Coast1411376 
AC East Coast211011  
AC Pennsylvania101  
AC Quebec101  
AC Greenland220  
AC Bermuda20215 
AC Florida25421  
AC Mississippi101  
AC Alabama20224 
Mexican Border381424  
AC Texas21219  
AC New Mexico312 Worthen's Sparow
AC Arizona81752 
AC North America21516  
Baja California633 1 extinct
Introduced Species23221 Skylark, Starling in 1886
Invasive Species20242Ibis & Cowbird
Totals26455 209 

The Cattle Ibis and Shining Cowbird are the only two species which appear to have been natural and explosive invaders of North America during the last 115 years. Of 23 introduced species (mostly parrots) only the Skylark and Starling were recognized in 1886. Baja California, Bermuda and Greenland combined have contributed only 5 additions to the 1886 list. Worthen's Sparrow is known from North America (North of Mexico) only by the type specimen collected in New Mexico.

Extinct Species

The Checklist includes several extinct species, including the Guadalupe Storm-Petrel, Labrador Duck, Great Auk, Passenger Pigeon, Carolina Parakeet, Ivory-billed Woodpecker, and Bachman's Warbler. The demise of the Ivory-billed Woodpecker has not yet been officially declared.

Revisions of Latin or English Names

Just as our language changes over time, so (often) do the names of birds. Most of the time there are excellent reasons for such changes. The table below summarizes changes which have taken place in the A.O.U. Checklist.

One of the reasons for the formation of the A.O.U. was to help bring about stability in taxonomic nomenclature throughout the world. The first Checklist included in the introductory material the Code or rules by which the Committee would be guided. The proposed Code was considered to be an improvement upon the Stricklandian Code of the British Association and those of several other organizations in Europe. Ultimately, a uniform code was adopted and its enforcement power was vested in the International Commission for Zoological Nomenclature (ICZN).

Many of the taxonomic name revisions appearing in the three Checklist editions subsequent to 1886 were the result of applying the agreed-upon rules of priority, where the first name published in the description of an organism (birds, in our case) must be the permanent official name. It took many years for the literature in many languages to be collated. Even today an obscure publication may come to light (recall Mendel's peas) which reveals an "earliest" name. To promote stability in nomenclature there is a provision in the International Code that permits a name that has been long in use to prevail over one recently rediscovered. The table below records six instances where the ICZN has suppressed a name to promote such stability.

There is discussion below the table to explain each of the categories of information. Notations in parentheses are those that will be found in the species listings (see index) on this website.

Revisions of Latin / English Names
  1.  Taxonomic Name Revisions  (R) 2924014114511933707
  2.  Due to ICZN Suppression of Names  (I) 0001326
  3.  Changes in Hyphenation  (H+ or -) 023264136
  4.  Changes of English Name  (E) 02351741793
  5.  Simple Change of English Spelling  (Esp) 0014207
  6.  Latin "i" vs. "ii" Ending Changes  (Zi) 5325222167
  7.  Latin Gender Ending Changes  (Z) 486138140
  8.  Personal Pronoun s' vs. s's Changes  (Qs) 00180817
  9.  Change of Qualifier Name (Qc) 103012805420206
10.  Qualifier Name Deleted (Q-) 0339316584
11.  Qualifier Name Added (Q+) 383520455116
12.  Total Changes/Actions Made ( 1-11 ) 51376218367284831379
13.  Number of Species Affected by (12) 4533420031524972 
14.  Previous Edition Species Affected 6%42%25%39%31%9% 
Years Between Checklists 91521262617* 
Annualized Changes/Year [*through 2000] 5.725.110.414.110.94.9* 

1. Taxonomic Name Revisions

Karl von Linné (better known as Linnaeus) established the system of binomial nomenclature in which all species have two (but today, sometimes three) names. The first name is the generic name. It defines the genus to which the organism is assigned. A genus (plural genera) may have from one to many species which are considered to be closely related by ancestry. The second name, or specific, must be unique to each species within a genus. Many species could have the specific name tyrannus but no two species within the same genus may be so named.

To Linnaeus, the genus was a very broad category for birds that were superficially similar. For instance, he placed all woodpeckers in just one genus. In 1758 he placed the Eastern Kingbird and Shrikes in the genus Lanius. By 1766 he had begun to refine his concepts somewhat and placed some flycatchers, including the Fork-tailed Flycatcher, in the genus Muscicapa. The table below shows some of the subsequent taxonomic revisions that affected these species.

To better reflect the perceived ancestry and relationships among species taxonomists "revise" accepted sequences or lists of birds based on studies of geographic distribution, physical body structure, genetic data, ecology, behavior and other measurable characteristics. It is often the case that a taxonomic revision lumps or splits species or moves a species to a new or different genus. These taxonomic decisions may require a change in nomenclature -- the names we assign to individual species.

In 1799, Lacepede made extensive revisions to Linnaeus' generic assignments. As shown below he erected or created the genera Muscivora and Tyrannus. Later, Swainson erected the genus Milvulus which is no longer in use today. When the first A.O.U. Checklist was established in 1886 it included the Kingbird, Tyrannus tyrannus and the Fork-tailed Flycatcher, Milvulus tyrannus.

ChecklistCommon NameScientific NameOriginal NameDescriber
1886Fork-tailed FlycatcherMilvulus tyrannusMuscicapa TyrannusLinnaeus 1766
1910Fork-tailed FlycatcherMuscivora tyrannus  
1985Fork-tailed FlycatcherTyrannus savanaTyrannus savanaVieillot 1808
1886-1998Eastern KingbirdTyrannus tyrannusLanius TyrannusLinnaeus 1758
   MilvulusSwainson 1825
   MuscivoraLacepede 1799
   TyrannusLacepede 1799

By 1910 the Fork-tailed Flycatcher was moved into the genus Muscivora and, by 1985, into Tyrannus. Obviously these revisions required a change in the bird's generic name. But another problem arose because a bird with the specific name tyrannus already existed in the genus Tyrannus. The matter is decided by the Law of Priority. The Kingbird's specific name tyrannus (1758) trumps the Fork-tailed's tyrannus (1766). Continuing to adhere to priority, the reviser found that the next available name for the Fork-tailed was Vieillot's name savana 1808.

My category "Taxonomic Name Revisions" includes nomenclatural changes made in the absence of any revision. I broadly include any change of the scientific name other than a change in name endings.

2. Due to ICZN Suppression of Names

When disputes over usage of names arise a petition may be filed with the International Commission on Zoological Nomenclature for adjudication. Decisions of the ICZN are binding, and virtually all scientific journals and publishers insist that authors use approved names. Only a few notations regarding ICZN name suppression are shown in the species listings because, in many cases, the suppressed name never appeared in one of the Checklists. ICZN rulings have also been applied to higher level names. For instance, we use the group name Gaviidae for Loons rather than the suppressed name Colymbidae.

3. Changes in Hyphenation

Only one hyphenated Latin name (san-blasiana, San Blas Jay) has appeared in a Checklist. However, many English names have been or are hyphenated. The trend toward hyphenating group names (Night-Heron, Turtle-Dove, Wood-Pewee) is, in my opinion, deplorable. It complicates indexing and may lead to failures, for example, in finding all Doves by simple computer searches.

4. Changes of English Name  and   5. Simple Change of English Spelling

These are self-evident. See notations in species listings. Changes are in red.

6. Latin "i" Ending Changes

Which is correct, cassini or cassinii? There appears to have been a bit of tug-of-war going on between successive Checklist committees or individuals. Advocates of classical Latin seem to have insisted that uniform, single-i endings were not only normative, but required. Such changes have almost ended, with victory in the camp of those who adhere to priority of names as established by authors. Proper Latin construction is preferred by the Code of Nomenclature. But original spelling of authors (except in specified instances) is the Law. A name honoring a person, that was originally misspelled, may be corrected.

7. Latin Gender Ending Changes

Here, classical Latin advocates win -- it's the Law. The Code states that specific name endings should agree with the gender of generic names. This doesn't eliminate arguments in some cases, but changing of   Latin endings has subsided almost to extinction. Examples of corrections are given here. Note that, for the two thrushes, the change in Latin ending was made to conform with the new generic gender.

SpeciesOriginal SpellingCorrected Ending
Pintado PetrelDaption capensisDaption capense
Mountain QuailOreortyx pictaOreortyx pictus
Spoon-billed SandpiperEurynorhynchus pygmeumEurynorhynchus pygmeus
Barn SwallowHirundo erythrogastraHirundo erythrogaster
Hermit ThrushHylocichla guttataCatharus guttatus
Swainson's ThrushHylocichla ustulataCatharus ustulatus

8. Personal Pronoun s' / s's Changes

Xantus's has won out over Xantus' in this category. It is to be hoped that this debate is over and done with (even if I do prefer s'.)

9-11. Qualifier/Adjective Additions, Deletions or Changes

These are self-evident. See notations in species listings. Changes are in red.

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AOUintro.htm  --  Updated 24 May, 2006   --   Send suggestions, corrections to Richard White