Editing Hummingbird (section)

=== Courtship dives ===

When courting, the male Anna's hummingbird ascends some {{Convert|35|m|abbr=on}} above a female, before diving at a speed of {{Convert|27|m/s|abbr=on}}, equal to 385 body lengths/sec &ndash; producing a high-pitched sound near the female at the [[nadir]] of the dive.<ref name="clark09">{{Cite journal |last=Clark |first=C.J. |year=2009 |title=Courtship dives of Anna's hummingbird offer insights into flight performance limits |journal=Proceedings of the Royal Society B: Biological Sciences |volume=276 |issue=1670 |pages=3047–052 |doi=10.1098/rspb.2009.0508 |pmc=2817121 |pmid=19515669}}</ref> This downward acceleration during a dive is the highest reported for any vertebrate undergoing a voluntary aerial maneuver; in addition to acceleration, the speed relative to body length is the highest known for any vertebrate. For instance, it is about twice the diving speed of [[peregrine falcon]]s in pursuit of prey.<ref name="clark09"/> At maximum descent speed, about 10&nbsp;g of gravitational force occur in the courting hummingbird during a dive (Note: G-force is generated as the bird pulls out of the dive).<ref name="clark09"/>{{efn|By comparison to humans, this is a G-force acceleration well beyond the threshold of causing near loss of [[consciousness]] (occurring at about +5 Gz) in [[fighter pilot]]s during operation of a [[fixed-wing aircraft]] in a high-speed [[banked turn]].<ref name="clark09"/><ref name="Akparibo">{{Cite book |last1=Akparibo |first1=Issaka Y. |url=https://www.ncbi.nlm.nih.gov/books/NBK430768 |title=Aerospace, gravitational effects, high performance |last2=Anderson |first2=Jackie |last3=Chumbley |first3=Eric |date=2020-09-07 |publisher=National Center for Biotechnology Information, US National Institute of Medicine |chapter=Aerospace Gravitational Effects |pmid=28613519}}</ref>}}

The outer tail feathers of male Anna's (''Calypte anna'') and ''Selasphorus'' hummingbirds (e.g., Allen's, calliope) vibrate during courtship display dives and produce an audible chirp caused by aeroelastic flutter.<ref name="clark08">{{Cite journal |last1=Clark |first1=C. J. |last2=Feo |first2=T.J. |year=2008 |title=The Anna's hummingbird chirps with its tail: A new mechanism of sonation in birds |journal=Proceedings of the Royal Society B: Biological Sciences |volume=275 |issue=1637 |pages=955–962 |doi=10.1098/rspb.2007.1619 |pmc=2599939 |pmid=18230592}}</ref><ref name="clark14">{{Cite journal |last=Clark|first= C.J. |year=2014 |title=Harmonic hopping, and both punctuated and gradual evolution of acoustic characters in Selasphorus hummingbird tail-feathers |journal=PLOS ONE |volume=9 |issue=4 |page=e93829 |bibcode=2014PLoSO...993829C |doi=10.1371/journal.pone.0093829 |pmc=3983109 |pmid=24722049 |doi-access=free}}</ref> Hummingbirds cannot make the courtship dive sound when missing their outer tail feathers, and those same feathers could produce the dive sound in a wind tunnel.<ref name="clark08"/> The bird can sing at the same frequency as the tail-feather chirp, but its small syrinx is not capable of the same volume.<ref>{{Cite journal |last1=Clark |first1=C. J. |last2=Feo |first2=T. J. |year=2010 |title=Why do Calypte hummingbirds "sing" with both their tail and their syrinx? An apparent example of sexual sensory bias |journal=The American Naturalist |volume=175 |issue=1 |pages=27–37 |doi=10.1086/648560 |pmid=19916787 |bibcode=2010ANat..175...27C |s2cid=29680714}}</ref> The sound is caused by the aerodynamics of rapid air flow past tail feathers, causing them to [[aeroelasticity|flutter]] in a [[vibration]], which produces the high-pitched sound of a courtship dive.<ref name="clark08"/><ref>{{Cite journal |last1=Clark |first1=C.J. |last2=Elias |first2=D.O. |last3=Prum |first3=R.O. |year=2013 |title=Hummingbird feather sounds are produced by aeroelastic flutter, not vortex-induced vibration |journal=Journal of Experimental Biology |volume=216 |issue=18 |pages=3395–403 |doi=10.1242/jeb.080317 |pmid=23737562 |doi-access=free}}</ref>

Many other species of hummingbirds also produce sounds with their wings or tails while flying, hovering, or diving, including the wings of the calliope hummingbird,<ref name="clark">{{Cite journal |last=Clark |first=C.J. |year=2011 |title=Wing, tail, and vocal contributions to the complex acoustic signals of courting Calliope hummingbirds |url=http://www.actazool.org/temp/%7BACDC40CC-89E0-41E6-A4B2-7C7FB6734F1E%7D.pdf |url-status=dead |journal=Current Zoology |volume=57 |issue=2 |pages=187–196 |doi=10.1093/czoolo/57.2.187 |archive-url=https://web.archive.org/web/20150716160821/http://www.actazool.org/temp/%7BACDC40CC-89E0-41E6-A4B2-7C7FB6734F1E%7D.pdf |archive-date=2015-07-16 |access-date=2015-05-31 |doi-access=free}}</ref> broad-tailed hummingbird, rufous hummingbird, Allen's hummingbird, and the [[streamertail]] species, as well as the tail of the Costa's hummingbird and the black-chinned hummingbird, and a number of related species.<ref>{{Cite web |last=Kovacevic |first=M.|date=2008-01-30 |title=Hummingbird sings with its tail feathers |url=http://www.cosmosmagazine.com/news/1829/hummingbird-sings-with-its-tail-feathers |url-status=dead |archive-url=https://web.archive.org/web/20120503042604/http://www.cosmosmagazine.com/news/1829/hummingbird-sings-with-its-tail-feathers |archive-date=2012-05-03 |access-date=2013-07-13 |publisher=Cosmos Magazine}}</ref> The [[harmonic]]s of sounds during courtship dives vary across species of hummingbirds.<ref name="clark14"/>