While humans have three color cones in the retina sensitive to red, green and blue light, birds have a fourth color cone that can detect ultraviolet light. A research team trained wild hummingbirds to ...

Structures and functions of bird’s eye. (a) Bird vision. (b) Deep central fovea and four types of cones. (c) Foveated vision and tetrachromatic vision. The eyes of raptors such as eagles can ...

(CNN) — Many types of birds — such as hummingbirds, peacocks and parrots — are vividly colorful, but birds-of-paradise are especially flamboyant with hues of emerald, lemon, cobalt and ruby. Now, ...