Editing Hummingbird (section)

==Flight ==
[[File:Hummingbird Aerodynamics of flight.jpg|thumb|left|A female ruby-throated hummingbird hovering in mid-air]]

Hummingbird flight has been studied intensively from an aerodynamic perspective using wind tunnels and high-speed [[video camera]]s. Two studies of rufous or Anna's hummingbirds in a wind tunnel used [[particle image velocimetry]] techniques to investigate the lift generated on the bird's upstroke and downstroke.<ref name="Warrick et al.">{{Cite journal |last1=Warrick |first1=Douglas R. |last2=Tobalske |first2=Bret W. |last3=Powers |first3=Donald R. |year=2005 |title=Aerodynamics of the hovering hummingbird |url=https://digitalcommons.georgefox.edu/cgi/viewcontent.cgi?article=1033&context=bio_fac |journal=Nature |volume=435 |issue=7045 |pages=1094–097 |bibcode=2005Natur.435.1094W |doi=10.1038/nature03647 |pmid=15973407 |s2cid=4427424|url-access=subscription }}</ref><ref>{{Cite journal |last1=Sapir |first1=N. |last2=Dudley |first2=R. |year=2012 |title=Backward flight in hummingbirds employs unique kinematic adjustments and entails low metabolic cost |journal=Journal of Experimental Biology |volume=215 |issue=20 |pages=3603–611 |doi=10.1242/jeb.073114 |pmid=23014570 |doi-access=free|bibcode=2012JExpB.215.3603S }}</ref> The birds produced 75% of their weight support during the downstroke and 25% during the upstroke, with the wings making a "figure 8" motion.<ref>{{Cite journal|last1=Tobalske |first1=Bret W. |last2=Warrick |first2=Douglas R. |last3=Clark |first3=Christopher J. |last4=Powers |first4=Donald R. |last5=Hedrick |first5=Tyson L. |last6=Hyder |first6=Gabriel A. |last7=Biewener |first7=Andrew A. |year=2007 |title=Three-dimensional kinematics of hummingbird flight |journal=J Exp Biol |volume=210 |issue=13 |pages=2368–382 |doi=10.1242/jeb.005686 |pmid=17575042 |doi-access=free|bibcode=2007JExpB.210.2368T }}</ref>

[[File:Hummingbird wake Pengo.svg|thumb|upright=0.7|Hummingbirds generate a trail of wake [[Vortex|vortices]] under each wing while hovering.<ref name="ucr">{{cite web |author1=University of California - Riverside |title=Study shows hovering hummingbirds generate two trails of vortices under their wings, challenging one-vortex consensus |url=https://phys.org/news/2013-02-hummingbirds-trails-vortices-wings-one-vortex.html |publisher=Phys.org |access-date=8 March 2023 |date=25 February 2013}}</ref><ref name="Pour">{{cite journal |last1=Pournazeri |first1=Sam |last2=Segre |first2=Paolo S. |last3=Princevac |first3=Marko |last4=Altshuler |first4=Douglas L. |title=Hummingbirds generate bilateral vortex loops during hovering: evidence from flow visualization |journal=Experiments in Fluids |volume=54 |issue=1 |date=2012-12-25 |issn=0723-4864 |doi=10.1007/s00348-012-1439-5 |page=1439|s2cid=253853891 |url= https://link.springer.com/article/10.1007/s00348-012-1439-5}}</ref>]]

Many earlier studies had assumed that [[lift (force)|lift]] was generated equally during the two phases of the wingbeat cycle, as is the case of insects of a similar size.<ref name="Warrick et al."/> This finding shows that hummingbird [[Levitation (physics)|hovering]] is similar to, but distinct from, that of hovering insects such as the [[hawk moth]].<ref name="Warrick et al."/> Further studies using [[electromyography]] in hovering rufous hummingbirds showed that [[muscle strain]] in the pectoralis major (principal downstroke muscle) was the lowest yet recorded in a flying bird, and the primary upstroke muscle (supracoracoideus) is proportionately larger than in other bird species.<ref>{{Cite journal |last1=Tobalske |first1=B.W. |last2=Biewener |first2=A.A. |last3=Warrick |first3=D.R. |last4=Hedrick |first4=T.L. |last5=Powers |first5=D.R. |year=2010 |title=Effects of flight speed upon muscle activity in hummingbirds |journal=Journal of Experimental Biology |volume=213 |issue=14 |pages=2515–523 |doi=10.1242/jeb.043844 |pmid=20581281 |doi-access=free|bibcode=2010JExpB.213.2515T }}</ref> Presumably due to rapid wingbeats for flight and hovering, hummingbird wings have adapted to perform without an [[alula]].<ref>{{Cite book |last=Videler|first= J.J.|url=https://books.google.com/books?id=5Xr9NZdgzP0C&q=hummingbird+alula+digit+is+reduced+and+immobile&pg=PA34 |title=Avian Flight |date=2005 |publisher=Oxford University Press, Ornithology Series |isbn=978-0-19-856603-8 |page=34}}</ref>

The giant hummingbird's wings beat as few as 12 times per second,<ref>{{Cite journal |last1=Fernández |first1=M.J. |last2=Dudley |first2=R. |last3=Bozinovic |first3=F. |year=2011 |title=Comparative energetics of the giant hummingbird (Patagona gigas) |journal=Physiological and Biochemical Zoology |volume=84 |issue=3 |pages=333–340 |doi=10.1086/660084 |pmid=21527824 |s2cid=31616893}}</ref> and the wings of typical hummingbirds beat up to 80 times per second.<ref name="bbc">{{Cite news |last=Gill |first=V. |date=30 July 2014 |title=Hummingbirds edge out helicopters in hover contest |work=BBC News |url=https://www.bbc.com/news/28563737 |access-date=1 Sep 2014}}</ref> As air density decreases, for example, at higher altitudes, the amount of power a hummingbird must use to hover increases. Hummingbird species adapted for life at higher altitudes, therefore, have larger wings to help offset these negative effects of low air density on lift generation.<ref>{{Cite journal |last1=Feinsinger |first1=Peter |last2=Colwell |first2=Robert K. |last3=Terborgh |first3=John |last4=Chaplin |first4=Susan Budd |date=1979 |title=Elevation and the Morphology, Flight Energetics, and Foraging Ecology of Tropical Hummingbirds |journal=The American Naturalist |volume=113 |issue=4 |pages=481–497 |doi=10.1086/283408 |bibcode=1979ANat..113..481F |issn=0003-0147 |s2cid=85317341}}</ref>

A slow-motion video has shown how the hummingbirds deal with rain when they are flying. To remove the water from their heads, they shake their heads and bodies, similar to a dog shaking, to shed water.<ref>{{Cite news |last=Morelle|first=R. |author-link=Rebecca Morelle |date=8 November 2011 |title=Hummingbirds shake their heads to deal with rain |work=BBC News |url=https://www.bbc.com/news/science-environment-15620024 |access-date=22 March 2014}}</ref> Further, when raindrops collectively may weigh as much as 38% of the bird's body weight, hummingbirds shift their bodies and tails horizontally, beat their wings faster, and reduce their wings' angle of motion when flying in heavy rain.<ref>{{Cite news |last=St. Fleur|first= N. |date=20 July 2012 |title=Hummingbird rain trick: New study shows tiny birds alter posture in storms |work=Huffington Post |format=video |url=http://www.huffingtonpost.com/2012/07/19/hummingbird-rain-video_n_1685752.html |access-date=22 March 2014}}</ref>

=== Wingbeats and flight stability ===
[[File:Hummingbird feeding closeup 2000fps.webm|thumb|Slow-motion video of hummingbirds feeding]]

The highest recorded wingbeat rate for hummingbirds during hovering is 99.1 per second, as measured for male woodstars (''Chaetocercus sp.'').<ref name=":0">{{Cite journal |last1=Wilcox |first1=Sean |last2=Clark |first2=Christopher |year=2022 |title=Sexual selection for flight performance in hummingbirds |url=https://academic.oup.com/beheco/article/33/6/1093/6686581 |journal=Behavioral Ecology |volume=33 |issue=6 |pages=1093–1106|doi=10.1093/beheco/arac075 |url-access=subscription }}</ref> Males in the genus ''[[Chaetocercus]]'' have been recorded above 100 beats per second during courtship displays.<ref name=":0" /> The number of beats per second increases above "normal" hovering while flying during courtship displays (up to 90 per second for the calliope hummingbird, ''Selasphorus calliope''); a wingbeat rate 40% higher than its typical hovering rate.<ref>{{Cite journal |last=Clark |first=C.J. |year=2011 |title=Wing, tail, and vocal contributions to the complex acoustic signals of courting Calliope hummingbirds |journal=Current Zool. |volume=57 |issue=2 |pages=187–196 |doi=10.1093/czoolo/57.2.187 |doi-access=free}}</ref>

During turbulent airflow conditions created experimentally in a [[wind tunnel]], hummingbirds exhibit stable head positions and orientation when they [[Bird flight#Hovering|hover]] at a feeder.<ref name="ravi">{{Cite journal |last1=Ravi |first1=Sridhar |last2=Crall |first2=James D. |last3=McNeilly |first3=Lucas |last4=Gagliardi |first4=Susan F. |last5=Biewener |first5=Andrew A. |last6=Combes |first6=Stacey A.|year=2015 |title=Hummingbird flight stability and control in freestream turbulent winds |journal=J Exp Biol |volume=218 |issue=Pt 9 |pages=1444–452 |doi=10.1242/jeb.114553 |pmid=25767146 |doi-access=free}}</ref> When wind gusts from the side, hummingbirds compensate by increasing wing-stroke [[amplitude]] and stroke plane angle and by varying these parameters asymmetrically between the wings and from one stroke to the next.<ref name=ravi/> They also vary the orientation and enlarge the collective [[surface area]] of their tail feathers into the shape of a [[hand fan|fan]].<ref name=ravi/> While hovering, the [[visual system]] of a hummingbird is able to separate apparent motion caused by the movement of the hummingbird itself from motions caused by external sources, such as an approaching predator.<ref name="goller"/> In natural settings full of highly complex background motion, hummingbirds are able to precisely hover in place by rapid coordination of vision with body position.<ref name="goller"/>