Human eyes have three types of retinal cones for detecting what we call "visible light." Many animals have a wider spectrum of detection, with their visible light extending from the ultraviolet to the infrared, and they have more types of cones for detecting these wavelengths. In the article by Tedore and Nilsson (2019), the authors examine the wavelengths related to the tetrachromatic vision of most terrestrial-foraging birds.
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