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 extant representatives of the reptile
class Archosauria, next to Testudines (turtles), the other class being the
Lepidosauria (Squamata: snakes, lizards), both belonging to the Diapsids,
itself together with the Synapsids (mammals)
forming the Amniotes (amnion = fetal tissue),
next to the amphibians
from the Anamniotes ("lower vertebrates": fishes and
amphibians, laying their eggs in water), part of the superclass tetrapods, 4-limbed vertebrates
(with fishes traditionally excluded, but cladistically included), in the
subphylum Vertebrates of the phylum Chordata, contrary to the phylum arthropods (invertebrate
joint-legged animals with an exoskeleton, and a segmented body), consisting of
the subphyla: 6-legged Hexapoda (insects, incl.
caterpillars with additional prolegs), 8-legged Chelicerata (spiders, scorpions;
crab spiders have 6 walking legs), 10/12/14-legged Pancrustacea (crabs, lobsters and
crayfish with 8 walking legs, shrimp, krill), and 16~1306-legged Myriapoda (millipedes, centipedes).
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 (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.
The
oldest undisputed fossil of a modern-style neornithean bird (without teeth) was
found in 2000 in the Maastricht Formation just over the border in Belgium by a
Dutch amateur paleontologist. This
became world news 20 years later, after the fossil of this Wonderchicken was
taken to the university of Cambridge in 2019 and called Asteriornis
maastrichtensis, closely related to birds of the extant superorder Galloanserae
such as chickens and ducks. It looks
like a chicken from the front, and a duck from behind, and is dated to around
66.8 to 66.7 million years old, less than a million years before the arrival of
the extinction-causing asteroid.
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): bird family and name changes 1990>2022
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 (2013: includes
GALAPAGOS FINCHES) |
|
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: |
||||||
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