Editing Hawk (section)

=== Eyesight ===
Hawks, like most birds, are [[tetrachromat]]s with four types of colour receptors in the eye. Unlike some birds, but similar to other diurnal raptors, most hawk species are violet-sensitive but cannot perceive ultraviolet light.<ref>{{cite journal |last1=Lind |first1=Olle |last2=Mitkus |first2=Mindaugas |last3=Olsson |first3=Peter |last4=Kelber |first4=Almut |title=Ultraviolet sensitivity and colour vision in raptor foraging |journal=Journal of Experimental Biology |date=15 May 2013 |volume=216 |issue=10 |pages=1819–1826 |doi=10.1242/jeb.082834|doi-access=free |pmid=23785106 }}</ref> Hawks also have relatively high visual acuity – the distance at which they can resolve an image – with [[red-tailed hawks]] reported to have 16.8 cycles per degree.<ref>{{Cite journal |last1=Hall |first1=M.I. |last2=Ross |first2=C.F. |date=2007 |title=Eye shape and activity patterns in birds |journal=Journal of Zoology |volume=271 |issue=4 |pages=437–444|doi=10.1111/j.1469-7998.2006.00227.x }}</ref> This is due to the large number of [[Photoreceptor cell|photoreceptor]]s in the [[retina]] (up to 1,000,000 per square mm in ''Buteo'', compared to 200,000 in [[humans]]), a high number of [[Neuron|nerves]] connecting these receptors to the brain, and an indented [[Fovea centralis|fovea]], which magnifies the central portion of the [[visual field]].<ref>{{cite web  | title = Hawks | publisher = beautyofbirds.com   | url = http://www.beautyofbirds.com/hawks.htm  | access-date = 2010-01-30 }}</ref><ref>{{cite web | last = Kirschbaum | first = Kari | title = Family Accipitridae | work = AnimalDiversity Web | publisher = University of Michigan Museum of Zoology  | url = http://animaldiversity.ummz.umich.edu/site/accounts/information/Accipitridae.html  | access-date = 2010-01-30 }}</ref><ref>{{cite news |last1=Nathan |first1=Raymond |title=Bird of preys |url=https://www.birdlife.org/news/2009/06/24/list-of-birds-of-prey/ |access-date=8 April 2023 |publisher=Birdlife.org}}</ref> Hawks additionally have two foveae (depressions in the retina with high photoreceptor density) in each eye, one centrally-placed and the other temporally-placed.<ref>{{Cite journal |last1=Mitkus |first1=Mindaugas |last2=Olsson |first2=Peter |last3=Toomey |first3=Matthew B. |last4=Corbo |first4=Joseph C. |last5=Kelber |first5=Almut |date=2017 |title=Specialized photoreceptor composition in the raptor fovea |journal=The Journal of Comparative Neurology |volume=525 |issue=9 |pages=2152–2163 |doi=10.1002/cne.24190|pmid=28199005 |pmc=6235456 }}</ref> Finally, the eyeball is elongated, placing the lens far from the retina and giving a long [[focal length]].<ref>{{Cite web |date=2023-11-25 |title=How Far Can Hawks Really See? (The Truth Explained) {{!}} Birdie Learning |url=https://birdielearning.com/how-far-can-hawks-see/#:~:text=Hawks%20have%20binocular%20vision,%20much%20like%20humans,%20which,long%20%E2%80%9Cfocal%20length%E2%80%9D,%20which%20produces%20a%20large%20image. |access-date=2024-10-18 |website=birdielearning.com |language=en-US}}</ref>