Editing Flightless bird (section)

==History==
===Origins of flightlessness===
Divergences and losses of flight within ratite lineage occurred right after the [[Cretaceous–Paleogene extinction event|K-Pg extinction event]] wiped out all [[Origin of birds|non-avian dinosaurs]] and large vertebrates 66&nbsp;million years ago.<ref name=":1">{{cite journal |pmid=22831877|year=2013|last1=Smith|first1=J. V.|title=Ratite nonmonophyly: Independent evidence from 40 novel Loci|journal=Systematic Biology|volume=62|issue=1|pages=35–49|last2=Braun|first2=E. L.|last3=Kimball|first3=R. T.|doi=10.1093/sysbio/sys067|doi-access=free}}</ref> The immediate evacuation of niches following the mass extinction provided opportunities for Palaeognathes to distribute and occupy novel environments. New ecological influences selectively pressured different taxa to converge on flightless modes of existence by altering them morphologically and behaviorally. The successful acquisition and protection of a claimed territory selected for large size and [[cursorial]]ity in Tertiary ancestors of ratites.<ref name="Phillips, M. J. 2010">{{Cite journal |pmid = 20525622|year = 2010|last1 = Phillips|first1 = M. J.|title = Tinamous and moa flock together: Mitochondrial genome sequence analysis reveals independent losses of flight among ratites|journal = Systematic Biology|volume = 59|issue = 1|pages = 90–107|last2 = Gibb|first2 = G. C.|last3 = Crimp|first3 = E. A.|last4 = Penny|first4 = D.|doi = 10.1093/sysbio/syp079|doi-access = free}}</ref> Temperate rainforests dried out throughout the Miocene and transformed into semiarid deserts, causing habitats to be widely spread across the growingly disparate landmasses. Cursoriality was an economic means of traveling long distances to acquire food that was usually low-lying vegetation, more easily accessed by walking.<ref name="Phillips, M. J. 2010"/> Traces of these events are reflected in ratite distribution throughout semiarid grasslands and deserts today.<ref name="Noble, J. C. 1991">{{cite journal |last=Noble |first=J. C. |year=1991 |title=On ratites and their interactions with plants |url=http://rchn.biologiachile.cl/pdfs/1991/1/Noble_1991.pdf |journal=Revista Chilena de Historia Natural |volume=64 |pages=85–118}}</ref>

[[Island gigantism|Gigantism]] and flightlessness in birds are almost exclusively correlated due to islands lacking [[mammal]]ian or [[Reptile|reptilian]] predators and competition.<ref>{{cite book |doi=10.1016/B978-0-323-99931-1.00012-X |chapter=Dwarfing and gigantism in quaternary vertebrates |title=Reference Module in Earth Systems and Environmental Sciences |date=2023 |last1=Palombo |first1=Maria Rita |last2=Moncunill-Solé |first2=Blanca |isbn=978-0-12-409548-9 }}</ref> However, ratites occupy environments that are mostly occupied by a diverse number of mammals.<ref name="Mitchell, K. 2014">{{Cite journal |pmid = 24855267|year = 2014|last1 = Mitchell|first1 = K. J.|title = Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution|journal = Science|volume = 344|issue = 6186|pages = 898–900|last2 = Llamas|first2 = B.|last3 = Soubrier|first3 = J.|last4 = Rawlence|first4 = N. J.|last5 = Worthy|first5 = T. H.|last6 = Wood|first6 = J.|last7 = Lee|first7 = M. S.|last8 = Cooper|first8 = A.|doi = 10.1126/science.1251981|bibcode = 2014Sci...344..898M|hdl = 2328/35953|s2cid = 206555952|hdl-access = free}}</ref> It is thought that they first originated through [[allopatric]] speciation caused by breakup of the supercontinent [[Gondwana]].<ref name="Baker, A. J. 2014"/> However, later evidence suggests this hypothesis first proposed by Joel Cracraft in 1974 is incorrect.<ref name="Cracraft, J. 1974">{{Cite journal | doi=10.1111/j.1474-919X.1974.tb07648.x|title = Phylogeny and Evolution of the Ratite Birds| journal=Ibis| volume=116| issue=4| pages=494–521|year = 2008|last1 = Cracraft|first1 = Joel|author-link1=Joel Cracraft}}</ref> Rather ratites arrived in their respective locations via a flighted ancestor and lost the ability to fly multiple times within the lineage.

[[Gigantism]] is not a requirement for flightlessness. The kiwi do not exhibit gigantism, along with [[tinamou]]s, even though they coexisted with the moa and rheas that both exhibit gigantism. This could be the result of different ancestral [[Bird flight|flighted bird]]s arrival or because of competitive exclusion.<ref name="Baker, A. J. 2014"/> The first flightless bird to arrive in each environment utilized the large flightless herbivore or omnivore niche, forcing the later arrivals to remain smaller. In environments where flightless birds are not present, it is possible that after the K/T Boundary there were no niches for them to fill. They were pushed out by other [[List of herbivorous animals|herbivorous mammals]].<ref name="Mitchell, K. 2014"/>

[[New Zealand]] had more species of flightless birds (including the [[Kiwi (bird)|kiwi]], several species of [[penguin]]s, the [[takahē]], the [[weka]], the moa, and [[List of New Zealand animals extinct in the Holocene|several other extinct species]]) than any other such location. One reason is that until the arrival of humans roughly a thousand years ago, there were no large mammalian land predators in New Zealand; the main predators of flightless birds were larger birds.<ref>{{cite web |url=http://www.savethekiwi.org.nz/AboutTheBird/NewZealandsIcon/KiwiCharacteristics/Flightless.htm |title=New Zealand's Icon:Flightless |access-date=2007-08-27 |archive-url=https://web.archive.org/web/20070818122353/http://www.savethekiwi.org.nz/AboutTheBird/NewZealandsIcon/KiwiCharacteristics/Flightless.htm <!-- Bot retrieved archive --> |archive-date=2007-08-18}}</ref>

====Independent evolution of flightlessness in Palaeognathes====
[[Ratite]]s belong to the superorder [[Palaeognathae]], which include the [[Flying and gliding animals|volant]] [[tinamou]], and are believed to have evolved flightlessness independently multiple times within their own group.<ref name=":0" /><ref name=":1" /><ref name="Phillips, M. J. 2010" /><ref name="Mitchell, K. 2014" /> Some birds evolved flightlessness in response to the absence of predators, for example on [[oceanic island]]s. Incongruences between ratite phylogeny and Gondwana geological history indicate the presence of ratites in their current locations is the result of a secondary invasion by flying birds.<ref>{{Cite journal |pmid = 22977150|pmc = 3479725|year = 2012|last1 = Haddrath|first1 = O.|title = Multiple nuclear genes and retroposons support vicariance and dispersal of the palaeognaths, and an Early Cretaceous origin of modern birds|journal = Proceedings. Biological Sciences|volume = 279|issue = 1747|pages = 4617–25|last2 = Baker|first2 = A. J.|doi = 10.1098/rspb.2012.1630}}</ref> It remains possible that the most recent common ancestor of ratites was flightless and the tinamou regained the ability to fly.<ref>{{Cite journal |pmid = 18765814|pmc = 2533212|year = 2008|last1 = Harshman|first1 = J.|title = Phylogenomic evidence for multiple losses of flight in ratite birds|journal = Proceedings of the National Academy of Sciences of the United States of America|volume = 105|issue = 36|pages = 13462–7|last2 = Braun|first2 = E. L.|last3 = Braun|first3 = M. J.|last4 = Huddleston|first4 = C. J.|last5 = Bowie|first5 = R. C.|last6 = Chojnowski|first6 = J. L.|last7 = Hackett|first7 = S. J.|last8 = Han|first8 = K. L.|last9 = Kimball|first9 = R. T.|last10 = Marks|first10 = B. D.|last11 = Miglia|first11 = K. J.|last12 = Moore|first12 = W. S.|last13 = Reddy|first13 = S.|last14 = Sheldon|first14 = F. H.|last15 = Steadman|first15 = D. W.|last16 = Steppan|first16 = S. J.|last17 = Witt|first17 = C. C.|last18 = Yuri|first18 = T.|doi = 10.1073/pnas.0803242105|bibcode = 2008PNAS..10513462H|doi-access = free}}</ref> However, it is believed that the loss of flight is an easier transition for birds than the loss and regain of flight, which has never been documented in avian history.<ref name="Phillips, M. J. 2010"/> Moreover, tinamou nesting within flightless ratites indicates ancestral ratites were volant and multiple losses of flight occurred independently throughout the lineage. This indicates that the distinctive flightless nature of ratites is the result of convergent evolution.<ref name="Smith, J. V. 2012"/>