Chickens have terrible night vision, but they’re capable of seeing colors – including vibrantly purple ultraviolet colors – that humans cannot. Researchers think chickens and other birds inherited their visual capabilities from their dinosaur ancestors. Because most dinosaurs weren’t nocturnal (active at night), they developed exceptional color perception and motion – detection vision for hunting a broad daylight.
Chickens have very few cones, and they are not especially sensitive. This difference between rod to cone ratio and the light sensitivities of cones in birds vs. mammals is explained because mammals all but disappeared from evolution long ago, and the only types of mammals that survived were nocturnal and insect eaters. Mammals that survived this evolutionary bottleneck re-developed colour vision after millions of years, but since we evolved our cones from a different starting point than birds (they evolved from dinosaurs, and never spent millennia as nocturnal creatures), we developed our colour vision a little differently. It’s another case of convergent evolution like whales and dolphins evolving to look like fish, because that’s the body type that works best in the water.
Picture Credit : Google