Editing Hummingbird (section)

==Sexual dimorphisms==

{{multiple image
|image1=Violet-tailed Sylph 2 JCB.jpg
|width1=150
|caption1=Male
|image2=Violet-tailed Sylph (f) JCB.jpg
|width2=90
|caption2=Female
|footer=Sexual dimorphism in [[violet-tailed sylph]]
}}

Hummingbirds exhibit sexual size dimorphism according to [[Rensch's rule]],<ref name="Colwell2000"/> in which males are smaller than females in small-bodied species, and males are larger than females in large-bodied species.<ref name="Lisle2013">{{Cite journal |last1=Lisle |first1=Stephen P. De |last2=Rowe |first2=Locke |date=2013-11-01 |title=Correlated Evolution of Allometry and Sexual Dimorphism across Higher Taxa |journal=The American Naturalist |volume=182 |issue=5 |pages=630–639 |doi=10.1086/673282 |pmid=24107370 |bibcode=2013ANat..182..630D |s2cid=25612107}}</ref> The extent of this sexual size difference varies among clades of hummingbirds.<ref name="Lisle2013"/><ref name="Berns2012">{{Cite journal |last1=Berns |first1=Chelsea M. |last2=Adams |first2=Dean C. |date=2012-11-11 |title=Becoming Different But Staying Alike: Patterns of Sexual Size and Shape Dimorphism in Bills of Hummingbirds |journal=Evolutionary Biology |volume=40 |issue=2 |pages=246–260 |doi=10.1007/s11692-012-9206-3 |issn=0071-3260 |s2cid=276492}}</ref> For example, the Mellisugini clade (bees) exhibits a large size dimorphism, with females being larger than males.<ref name="Berns2012"/> Conversely, the Lesbiini clade (coquettes) displays very little size dimorphism; males and females are similar in size.<ref name="Berns2012"/>
Sexual dimorphisms in bill size and shape are also present between male and female hummingbirds,<ref name="Berns2012"/> where in many clades, females have longer, more curved bills favored for accessing nectar from tall flowers.<ref name="Temeles2010">{{Cite journal |last1=Temeles |first1=Ethan J. |last2=Miller |first2=Jill S. |last3=Rifkin |first3=Joanna L. |date=2010-04-12 |title=Evolution of sexual dimorphism in bill size and shape of hermit hummingbirds (Phaethornithinae): a role for ecological causation |journal=Philosophical Transactions of the Royal Society of London B: Biological Sciences |volume=365 |issue=1543 |pages=1053–063 |doi=10.1098/rstb.2009.0284 |issn=0962-8436 |pmc=2830232 |pmid=20194168}}</ref> For males and females of the same size, females tend to have larger bills.<ref name="Berns2012"/>

Sexual size and bill differences likely evolved due to constraints imposed by courtship, because mating displays of male hummingbirds require complex aerial maneuvers.<ref name="Colwell2000"/> Males tend to be smaller than females, allowing conservation of energy to [[forage]] competitively and participate more frequently in courtship.<ref name="Colwell2000">{{Cite journal |last=Colwell |first=Robert K. |date=2000-11-01 |title=Rensch's Rule Crosses the Line: Convergent Allometry of Sexual Size Dimorphism in Hummingbirds and Flower Mites |journal=The American Naturalist |volume=156 |issue=5 |pages=495–510 |doi=10.1086/303406 |pmid=29587514 |bibcode=2000ANat..156..495C |s2cid=4401233}}</ref> Thus, [[sexual selection]] favors smaller male hummingbirds.<ref name="Colwell2000"/>

Female hummingbirds tend to be larger, requiring more energy, with longer beaks that allow for more effective reach into crevices of tall flowers for nectar.<ref name="Temeles2010"/> Thus, females are better at foraging, acquiring flower nectar, and supporting the energy demands of their larger body size.<ref name="Temeles2010"/> [[Directional selection]] thus favors the larger hummingbirds in terms of acquiring food.<ref name="Lisle2013"/>

Another evolutionary cause of this sexual bill dimorphism is that the selective forces from competition for nectar between the sexes of each species drives sexual dimorphism.<ref name="Berns2012"/> Depending on which sex holds territory in the species, the other sex having a longer bill and being able to feed on a wide variety of flowers is advantageous, decreasing [[intraspecific competition]].<ref name="Temeles2010"/> For example, in species of hummingbirds where males have longer bills, males do not hold a specific territory and have a [[lek mating]] system.<ref name="Temeles2010"/> In species where males have shorter bills than females, males defend their resources, so females benefit from a longer bill to feed from a broader range of flowers.<ref name="Temeles2010"/>

===Feather colors===
[[File:AnnasHummingbirdPaloAltoNorvig.jpg|upright|thumb|Male Anna's hummingbird showing iridescent crown and gorget feathers]]

The hummingbird plumage coloration [[gamut]], particularly for blue, green, and purple colors in the gorget and crown of males, occupies 34% of the total color space for bird feathers.<ref name=venable/> White (unpigmented) feathers have the lowest incidence in the hummingbird color gamut.<ref name=venable/> Hummingbird plumage color diversity evolved from sexual and social selection on plumage coloration, which correlates with the rate of hummingbird species development over millions of years.<ref name=venable/> Bright plumage colors in males are part of aggressive [[competition (biology)|competition]] for flower resources and mating.<ref name=venable/><ref name="learner"/> The bright colors result from [[pigment]]ation in the feathers and from [[Prism (optics)|prismal]] cells within the top layers of feathers of the head, gorget, breast, back and wings.<ref name=venable/><ref name="williamson">{{Cite book |last=Williamson S |url=https://books.google.com/books?id=XtZ1xotyal8C&q=Iridescent+colors+hummingbird+feathers.&pg=PA28 |title=A Field Guide to Hummingbirds of North America. Section: Plumage and Molt |publisher=Houghton Mifflin Harcourt |year=2001 |isbn=978-0-618-02496-4 |pages=13–18}}</ref> When [[sunlight]] hits these cells, it is split into wavelengths that reflect to the observer in varying degrees of intensity,<ref name="williamson"/> with the feather structure acting as a [[diffraction grating]].<ref name="williamson"/> Iridescent hummingbird colors result from a combination of refraction and pigmentation, since the diffraction structures themselves are made of [[melanin]], a pigment,<ref name=venable/><ref name="learner">{{Cite web |date=2015 |title=Hummingbird characteristics |url=http://www.learner.org/jnorth/search/HummerNotes1.html |url-status=dead |archive-url=https://web.archive.org/web/20161111085045/http://learner.org/jnorth/search/HummerNotes1.html |archive-date=2016-11-11 |access-date=2010-08-30 |website=learner.org |publisher=Annenberg Learner, The Annenberg Foundation}}</ref> and may also be colored by [[carotenoid]] pigmentation and more subdued black, brown or gray colors dependent on melanin.<ref name="williamson"/>

By merely shifting position, feather regions of a muted-looking bird can instantly become fiery red or vivid green.<ref name="williamson"/> In courtship displays for one example, males of the colorful Anna's hummingbird orient their bodies and feathers toward the sun to enhance the display value of iridescent plumage toward a female of interest.<ref>{{Cite journal |last=Hamilton|first= W.J. |year=1965 |title=Sun-oriented display of the Anna's hummingbird |url=https://sora.unm.edu/sites/default/files/journals/wilson/v077n01/p0038-p0044.pdf |journal=The Wilson Bulletin |volume=77 |issue=1}}</ref>

One study of Anna's hummingbirds found that dietary [[protein]] was an influential factor in feather color, as birds receiving more protein grew significantly more colorful [[crown (anatomy)|crown]] feathers than those fed a low-protein diet.<ref name="jeb">{{Cite journal |author1=Meadows, M.G. |author2=Roudybush, T.E. |author3=McGraw, K.J. |year=2012 |title=Dietary protein level affects iridescent coloration in Anna's hummingbirds, ''Calypte anna'' |journal=Journal of Experimental Biology |volume=215 |issue=16 |pages=2742–750 |doi=10.1242/jeb.069351 |pmc=3404802 |pmid=22837446|bibcode=2012JExpB.215.2742M }}</ref> Additionally, birds on a high-protein diet grew yellower (higher [[hue]]) green tail feathers than birds on a low-protein diet.<ref name="jeb"/>