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Alula
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{{Short description|Small projections on the wings of birds}} {{About|the anatomy of a bird's wing}} [[File:Alula.png|thumb|280px|alt=Drawing of the various parts of a bird's wing|Location of the alula on a bird's wing]] The '''alula''' {{IPAc-en|'|æ|l|j|U|l|@}}, or '''bastard wing''', (plural ''alulae'') is a small projection on the [[anterior]] edge of the [[wing]] of modern [[bird]]s and a few [[non-avian dinosaur]]s. The word is [[Latin]] and means "winglet"; it is the [[diminutive]] of ''ala'', meaning "wing". The alula is the freely moving first digit, a bird's "thumb", and typically bears three to five small [[flight feather]]s, with the exact number depending on the [[species]]. There also are minor [[covert feather]]s overlying the flight feathers. Like the larger [[flight feather]]s found on the wing's trailing edge, these alula feathers are asymmetrical, with the shaft running closer to anterior edge. ==Function== [[File:Haliaeetus leucocephalus2.jpg|thumb|200px|alt=A large bird landing on its nest|Adult [[bald eagle]] landing, showing the alula in action]] In most situations, the alula is held flush against the wing; however, it can be manipulated. When flying at slow speeds or landing, the bird moves its alula slightly upwards and forward, which creates a small slot on the wing's leading edge. This functions in the same way as the [[Leading edge slats|slats]] on the leading edge of the wing of an aircraft, allowing the wing to achieve a higher than normal [[angle of attack]] – and thus [[lift (force)|lift]] – without resulting in a [[stall (flight)|stall]].<ref>{{Harvnb|Ehrlich|Dobkin|Wheye|Pimms|1994|p=219}}</ref> The tip of the alula forms a tiny vortex, acting similar to a [[vortex generator]], that forces the airflow over the wing to better bind to it.<ref>{{cite web|url=http://www.sciencedaily.com/releases/2015/06/150605103008.htm |title=Small vortex on the wing makes the elegance of birds' flight |author=Laboratory of Behavioral Ecology and Evolution at Seoul National University |date=5 June 2015 |access-date=5 June 2015}}</ref> During stretching of the wing down toward the ground, the alula is abducted from the wing and can be clearly viewed. In falcons, the alula is more prominent, and provides a degree of control when the wing is cupped or tucked in a dive/stoop. The alulae are particularly notable in [[peregrine falcon]]s.{{Citation needed|reason=Unsourced statement that goes against previously sourced statements.|date=April 2021}} ==In ancient birds== The presence of an alula has been confirmed in several now-[[extinct]] ancient relatives of [[Neornithes|modern bird]]s, including ''[[Eoalulavis hoyasi]]'' (an [[Enantiornithes|enantiornithine]] from the mid-[[Cretaceous]], 115<ref>{{Harvnb|Sanz|Chiappe|Pérez-Moreno|Buscalioni|1996}}</ref> [[mya (unit)|mya]]) and the earlier ''[[Protopteryx fengningensis]]''.<ref>{{Harvnb|Zhang|Zhou|2000}}</ref> Since these [[species]] are not closely related to modern birds, either the alula [[evolved]] twice, or it did so more than 130 million years ago. ==See also== *[[Origin of birds#Digit homology|Alular digit homology]] *[[Bird flight]] *[[Leading edge slot]], the man-made equivalent on fixed-wing aircraft ==Citations== {{Reflist}} ==References== {{Commons category}} * {{citation |last1=Ehrlich |first1=Paul R. |last2=Dobkin |first2=David S. |last3=Wheye |first3=Darryl |last4=Pimms |first4=Stuart L. |title=The Birdwatcher's Handbook |year=1994 |publisher=Oxford University Press |isbn=0-19-858407-5 |url-access=registration |url=https://archive.org/details/birdwatchershand00ehrl }} * {{citation|first1=J. L.|last1=Sanz| first2=L. M. | last2=Chiappe| first3=B. P. | last3=Pérez-Moreno| first4=A. D. | last4=Buscalioni| first5=J. J. | last5=Moratalla| first6=F. | last6=Ortega| first7=F. J. | last7=Poyato-Ariza |journal=[[Nature (journal)|Nature]]|title=An Early Cretaceous bird from Spain and its implications for the evolution of avian flight|date=1996-08-01|volume=382|issue=6590| pages=442–445|doi=10.1038/382442a0|bibcode=1996Natur.382..442S|s2cid=4284528}} * {{citation |last1=Zhang |first1=Fucheng |last2= Zhou |first2= Zhonghe |title=A Primitive Enantiornithine Bird and the Origin of Feathers |pages=1955–1959 |journal=Science |date=8 December 2000 |volume=290 |issue=5498 |doi=10.1126/science.290.5498.1955 |pmid=11110660|bibcode=2000Sci...290.1955Z }} {{Feather-tracts}} {{Birds}} [[Category:Feathers]] [[Category:Bird anatomy]]
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