25 YEARS OF EVOLUTIONARY BIRD TAXONOMY since 1990

 

Avian evolution

Birds are avian dinosaurs and evolved from theropod dinosaurs during the late Jurassic (around 165–150 million years ago) and their classic small, lightweight, feathered, and winged body plan was pieced together gradually over tens of millions of years of evolution rather than in one burst of innovation. Most birds have four toes, with the fifth toe at ground dwelling birds like fowl sometimes evolved into a small spike at the back of the lower leg. Flightless birds, as well as button-quails, bustards and some tinamous and woodpeckers, and most Charadriiformes (shorebirds, gulls, auks) have three toes (with the hind toe vestigial or absent), while the Ostrich is the only extant bird with two toes on each foot.

Aves and a sister group, the order Crocodilia, contain the only living representatives of the reptile clade Archosauria. Birds descended from forest dwelling reptiles that evolved the capacity to glide from tree to tree or from ground dwellers that jumped or flew into trees for safety.

At the end of the Maastrichtian (72.1 to 66 million years ago, late Cretaceous), the non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is linked to an asteroid about 10 to 15 kilometres wide hitting the earth in the coastal waters of the Gulf of Mexico, leaving the Chicxulub Crater.

Santiago Claramunt and Joel Cracraft in 2015 found that the most recent common ancestor of modern birds (Neornithes: 9,200 taxonomic species in 1990, 10,000 in 2013, now 10,800) inhabited South America around 95 million years ago, but it was not until the extinction event that Neornithes began to diversify rapidly around the world. The non-Passerines (3,800 taxonomic species in 1990, 4,000 in 2013, now 4,300) used two main dispersion routes: reaching the Old World through North America, facilitated by an inter-American land bridge during the Paleocene (66 to 56 million years ago), and reaching Australia and Zealandia through Antarctica during the Paleogene (66 to 23 million years ago).

The Passerines, also known as songbirds or perching birds (differing from the non-Passerines in having the vocal organ highly developed and having independent, flexible toes, with one pointing backwards, ideal for grasping perches) emerged in eastern Gondwana, in the late Paleocene or early Eocene, around 50 million years ago. The Beringian land bridge and the warm temperatures of the Late Eocene (33 million years ago) could have provided a plausible route for dispersal to North America from Asia. But it is possible that New World suboscines originated in South America after trans-Antarctic separation from oscines in Australia. Suboscines (1,100 taxonomic species in 1990, 1,300 in 2013, now 1,350) differ from oscines (4,300 taxonomic species in 1990, 4,700 in 2013, now over 5,100) in having a simplifies syrinx (the ‘vocal cord’ of birds) musculature.

Avian taxonomic radiation

Between 1990 and 2013, one out of every six non-Passerines changed its genus name, while one out of every twelve changed its family name (with 2% changing both). About one out of every four of the Passerines changed its genus name, while one out of every three changed its family name (with 8% changing both).

Some 225 species were ousted, the most downgraded to subspecies, but 10 hummingbirds appeared to be hybrids
Another 20 appeared to be no longer extant.

About 1000 subspecies were upgraded to species, a burdensome process because of ongoing uncertainties about the details of both the definition of (sub)species and the evolutionary mechanism of speciation through which new species are created. Over 50 species were found new.

A subspecies is a geographically and morphologically defined population (or group of populations) of a species. Individuals from different subspecies of the same species are presumably interfertile. If they were known to be otherwise, they would be named as different species.

Following the Poland zoologist and entomologist Roman Bohdan Hołyński, the "current fashion of split first and think later (if at all)..." (quote of U.S. ornithologist Michael G. Harvey) is increasingly spreading, partly as a result of propagation of cladistic classifications, making "necessary" to split more and more well defined, homogeneous taxa only because somebody considers them "paraphyletic". 

In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—monophyletic subgroups or clades. The group is said to be paraphyletic with respect to the excluded subgroups.

Gaurav Vaidya, Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, Colorado, USA: We identified 142 lumps and 95 splits across sixty-three versions of the AOU Check-List and found that while lumping rates have markedly decreased since the 1970s, splitting rates are accelerating. We found that 74% of North American bird species recognized today have never been corrected (i.e., lumped or split) over the period of the checklist, while 16% have been corrected exactly once and 10% have been corrected twice or more. Since North American bird species are known to have been extensively lumped in the first half of the 20th century with the advent of the biological species concept, we determined whether most splits seen today were the result of those lumps being recorrected. We found that 5% of lumps and 23% of splits fully reverted previous corrections, while a further 3% of lumps and 13% of splits are partial reversions. These results show a taxonomic correction process with moderate levels of recorrection, particularly of previous lumps. However, 81% of corrections do not revert any previous corrections, suggesting that the majority result in novel circumscriptions not previously recognized by the Check-List.

Our results show a clear period of lumping in the 1920s to the 1980s, followed by a period of rapid splitting in the AOU checklist. 19.4% of all lumps and splits in our dataset are full or partial reversions of a previous correction (i.e. lump or split), 74% of which are splits reverting a previous lump. Reversions are clearly a part of the current period of splitting, but the vast majority (64.2%) of splits do not partially or fully revert a previous lump.

The Dutch ornithologist George Sangster points out that increasing numbers of bird species result from taxonomic progress, not taxonomic inflation: a point often overlooked in discussions about taxonomic instability is that, in the 1900s to 1940s, many thousands of bird species have been downgraded to subspecific rank and combined into large variable polytypic species. Thus, whereas 18,939 species of birds were recognized in 1909, only 8,590 species were recognized by 1951, a reduction of 55 per cent in just over 40 years. Most of these rearrangements were made without information on diagnostic character states, reproductive barriers or phylogenetic relationships. Not surprisingly, this upheaval has had a profound and lasting influence on avian taxonomy. Since that period, the evolutionary distinctiveness of many taxa has been rediscovered. Thus, the second half of the twentieth century has shown a trend opposite to that of the first half of the twentieth century. A high proportion (almost 80%) of newly proposed species since 1950 was originally described as species but subsequently downgraded to the subspecies level. Therefore, most splits since the 1950s overturn previous decisions to combine species.

Passerines comprise some 6,500 extant species, representing more than 60% of extant avian diversity. Since the 1990s, new data have elucidated the diversity of and relationships among a number of major passerine lineages, resulting in the expansion of the number of recognized passerine families (~idae) from 74 in 1990, 96 in 2003 to 135 in 2013, and 143 in 2020. For all birds, these numbers are 173, 235, and 251 respectively. The number of bird orders (~formes) rose from under 30 to 40.

China currently ranks at the top of Asia with 111 different bird families along with India, and in the world only Indonesia ranks higher 125 (109 in the Asian part of Indonesia). With 1,425 different species, China has 69 more than India (Asian Indonesia has 1,455; with the Indonesian part of Papua: 1,784). But around 2000 (according to the H&M 1994 checklist, revised in 2003), China and Indonesia (including Papua) were both at the top with 94 families each. Colombia has the most species: 1994 (and 90 families).

Nearly 50 chats, and 23 ‘thrushes’ keeping their English names (robin, nightingale, bluethroat), formerly in Turdidae (Thrushes and Chats), moved to Muscicapidae (Chats and Flycatchers)
18 sparrows were split from Ploceidae (then Weavers and Sparrows) to their own family Passeridae (Sparrows, Snowfinches and allies)
17 parrotbills were split from Panuridae, leaving the Bearded Reedling, to Sylviidae (now Sylvia Warblers, Parrotbills and allies)
32 Euphonia and the Chlorophonia species moved from Emberizidae (Thraupinae) to Fringillidae
22 Cardinals moved from Emberizidae (Cardinalinae) to Thraupidae
17 Tanagers moved from Emberizidae (Thraupinae) to Cardinalidae
133 Grassquits, Seedeaters, finches moved from Emberizidae (Emberizinae) to Thraupidae

The 2019 Clements check list recognizes 32,500 (sub)species, 11,500 non-Passerines, nearly 21,000 Passerines, of which 1,250 Tyrannidae (Tyrant Flycatchers), 1,150 Thraupidae (Tanagers and Allies) and nearly 1,100 Furnariidae (Ovenbirds and Woodcreepers), all New World; Muscicapidae (Old World Flycatchers) also has over 1,000; the orders Caprimulgiformes (Hummingbirds, Swifts, Nightjars, others) 1,600 and Piciformes (Woodpeckers, Toucans, Barbets, Honeyguides) 1,250.

The 2021 IOC World Bird List 11.1 contains 10,806 extant species classified in 40 Orders, 251 Families and 2,352 Genera. The list also includes 19,990 subspecies, total 30,796.

Not listed in the taxonomic check lists, some 1,500 domestic breeds of doves, chickens, canaries, ducks, geese, finches (waxbills), parrots and cockatiels (without a scientific name) should be added.

50 years of bird taxonomic ‘evolution’ of selected Passerine families (~idae) and subfamilies (~inae):

up to 1960s and over

H&M 1980

1960s~1980s

H&M 1990

1990s

H&M 2003 (2013)

H&M 2003 (2013)

FRINGILLIDAE

FRINGILLIDAE

FINCHES

FRINGILLIDAE

FINCHES

FRINGILLIDAE

FINCHES AND HAWAIIAN HONEYCREEPERS

Fringillinae

FRINGILLINAE

 

FRINGILLINAE

FRINGILLINAE

Carduelinae

CARDUELINAE

CARDUELINAE

CARDUELINAE

> 

DREPANIDIDAE

HAWAIIAN HONEYCREEPERS

DREPANIDIDAE

DREPANIDINAE

2013 > in Carduelinae

Geospizinae

> inside Emberizinae

GALAPAGOS FINCHES

EUPHONIINAE

2013 insertion

EMBERIZIDAE

BUNTINGS, TANAGERS

EMBERIZIDAE

EMBERIZIDAE

BUNTINGS AND ALLIES, 2013: OLD WORLD BUNTINGS

Emberizinae

EMBERIZINAE

BUNTINGS, NEW WORLD SPARROWS

EMBERIZINAE

BUNTINGS     2013: partly >

PASSERELLIDAE

NEW WORLD SPARROWS AND ALLIES

Richmondeninae*

CARDINALINAE

or PYRRHULOXIINAE

CARDINALINAE

CARDINALS

CARDINALIDAE

CARDINALS, GROSBEAKS AND ALLIES *

THRAUPIDAE

THRAUPINAE

TANAGERS

THRAUPINAE

TANAGERS

THRAUPIDAE

TANAGERS

CATAMBLYRHYNCHIDAE

CATAMBLYRHYNCHINAE PLUSH-CAPPED FINCH

CATAMBLYRHYNCHINAE

PLUSH-CAPPED FINCH

PLUSHCAP (1994~2013 incertae sedis)

TERSINIDAE

TERSININAE

SWALLOW TANAGER

TERSININAE

SWALLOW TANAGER

PARULIDAE

PARULIDAE

NEW WORLD WARBLERS

PARULIDAE

PARULINAE

 

COEREBINAE

Bananaquit

COEREBIDAE

Bananaquit

Bananaquit

ICTERIDAE

ICTERIDAE

NEW WORLD BLACKBIRDS

ICTERIDAE

NEW WORLD BLACKBIRDS

ICTERIDAE

NEW WORLD BLACKBIRDS

MUSCICAPIDAE

MUSCICAPIDAE

THRUSHES, WARBLERS ETC.

MUSCICAPIDAE

OLD WORLD FLYCATCHERS

MUSCICAPIDAE

CHATS AND FLYCATCHERS

MUSCICAPINAE

MUSCICAPINAE

FLYCATCHERS

PLATYSTEIRINAE

PUFF-BACK AND WATTLED FLYCATCHERS

PLATYSTEIRIDAE

PLATYSTEIRIDAE

WATTLE-EYES AND BATISES

MONARCHINAE˅

MONARCHINAE**

MONARCH FLYCATCHERS

MONARCHIDAE

MONARCHS AND FANTAILS

MONARCHIDAE

MONARCHS

RHIPIDURINAE˅

RHIPIDURINAE**

FANTAIL FLYCATCHERS

> in Monarchidae

RHIPIDURIDAE

FANTAILS

PACHYCEPHALINAE

PACHYCEPHALINAE

WHISTLERS

PACHYCEPHALIDAE

WHISTLERS

PACHYCEPHALIDAE

WHISTLERS

TURDIDAE

TURDINAE

THRUSHES AND CHATS

TURDIDAE

THRUSHES AND CHATS

TURDIDAE

THRUSHES

TIMALIIDAE

TIMALIINAE

BABBLERS

TIMALIIDAE

BABBLERS

TIMALIIDAE

BABBLERS, PARROTBILLS, 2013: SCIMITAR BABBLERS

CINCLOSOMATINAE

ORTHONYCHINAE

LOGRUNNERS and ALLIES

ORTHONYCHIDAE

LOGRUNNERS and ALLIES

ORTHONYCHIDAE

LOGRUNNERS

PICATHARTIDAE

PICATHARTINAE

ROCKFOWL

PICATHARTIDAE

BALD CROWS

EUPETIDAE

ROCKFOWL, ROCKJUMPER AND RAIL-BABBLER

PARADOXORNITHIDAE

PANURINAE

or PARADOXORNITHINAE

PANURIDAE

PARROTBILLS

PANURIDAE

BEARDED REEDLING  (2003~2013 in TIMALIIDAE)

SYLVIIDAE

SYLVIIDAE

OLD WORLD WARBLERS

SYLVIIDAE

OLD WORLD WARBLERS, 2013: + PARROTBILLS

SYLVIINAE

SYLVIINAE

OLD WORLD WARBLERS

> from Sylviidae

CISTICOLIDAE

CISTICOLAS

REGULINAE

REGULINAE

(H&M 1980 in Sylviinae ↑)

> in Sylviidae

REGULIDAE

GOLDCRESTS OR KINGLETS

HYLIINAE

(H&M 1980 in Sylviinae ↑)

POLIOPTILINAE

POLIOPTILINAE

GNATWRENS

POLIOPTILIDAE

GNATCATCHERS

POLIOPTILIDAE

GNATCATCHERS

MALURINAE

MALURINAE

AUSTRALIAN WRENS

MALURIDAE

AUSTRALASIAN WRENS

MALURIDAE

FAIRYWRENS AND GRASSWRENS

PLOCEIDAE

PLOCEIDAE

WEAVERS AND SPARROWS

PLOCEIDAE

WEAVERS AND SPARROWS

PLOCEIDAE

WEAVERS

PLOCEINAE

PLOCEINAE

PLOCEINAE

PASSERINAE˅

PASSERINAE

PASSERINAE

PASSERIDAE

SPARROWS, SNOWFINCHES AND ALLIES

VIDUINAE

VIDUINAE

 sometimes in ↓

VIDUINAE

VIDUIDAE

INDIGOBIRDS

ESTRILDINAE˅

ESTRILDIDAE

WAXBILLS

ESTRILDIDAE

WAXBILLS

ESTRILDIDAE

WAXBILLS

 

up to 1960s and over

H&M 1980

1960s~1980s

H&M 1990

1990s

H&M 2003 (2013)

H&M 2003 (2013)

* AOU 1970s: Cardinalinae

** elsewhere in MUSCICAPINAE

˅ Voous 1977: ~idae families

not all subfamilies are shown

* incl. NEW WORLD BUNTINGS

more precise changes:

Passerines name and family changes, sorted by 1990 families

Passerines name and family changes, sorted by 2013 families

 

Biogeographical distribution

The far most non-Passerine species are found in the Neotropical biogeographical area, followed by Australasian, Afrotropical and Oriental (each over half the Neotropical number), while Eastern Palearctic, Nearctic and Western Palearctic are under half of the level of the former three areas

Similar ratios apply to the Passerines, but here the Australasian area is last of the ‘second three’, while Nearctic and Western Palearctic areas are the only where the number of non-Passerine species exceeds that of the Passerines

Ben Holt in 2013 chose to let Palearctic include Alaska, Northern Canada and Greenland, as well as Hawaii and Taiwan, and Nearctic to include Mexico down to the Isthmus of Tehuantepec. This ousts Phylloscopidae (Arctic Warbler) and Muscicapidae (Northern Wheatear) from the New World and Laniidae (Shrikes) from the Neotropical area.

Only five Passerine families are global (except for introduced birds): Corvidae, Motacillidae, Alaudidae, Hirundinidae and Turdidae (Crows and Jays, Wagtails and Pipits, Larks, Swallows and Thrushes).

WP

Western Palearctic

Europe, North Africa, Middle East (excl. South Arabia)

EP

Eastern Palearctic

Siberia, the 'stans', Mongolia, China down to Yangtze, Korea, Japan

AF

Afrotropical

Africa sub-Sahara + Southern Arabia

OR

Oriental

Asia south of Himalayas, Yangtze, up to Wallace line

NA

Nearctic

North America down to central Mexico

NT

Neotropical

South America up to central Mexico

AP

Australasian

Oceania incl. Wallacea

 

Regions quoted from:
The (Hamlyn) Photographic Guide to the Birds of the World by Dr. Andrew Gosler, 1991 Mallard Press

Alcidae, Muscicapidae, Phylloscopidae, Sylviidae (or Paradoxornithidae with Wrentit transferred), are the only New World families that are not in the Neotropical area.

Australasia has been the only area where Passerine families exceed non-Passerine families, but Eastern Palearctic and Oriental joined with newly created families. Most non-Passerine families are found in the Afrotropical area.

Some family and genus names sometimes are confusing.

The avian taxonomic radiation

With the 2013-2014 Howard and Moore checklist the last, here is a survey of bird family and order changes over the period 1990~2021, with the families sorted following the 2021 IOC. Here are Specific taxonomic anomalies.

 


Sources: The Howard and Moore complete checklist of the birds of the world; Wikipedia
S. Claramunt, J. Cracraft, A new time tree reveals Earth history’s imprint on the evolution of modern birds. Sci. Adv. 1, e1501005 (2015)
Sangster G. Increasing numbers of bird species result from taxonomic progress, not taxonomic inflation. Proc Biol Sci. 2009 Sep;276(1670) 3185-3191. doi:10.1098/rspb.2


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