Birds do see in color. Birds that are active during daylight hours have the best color vision and, conversely, birds active at night usually have very good night vision. I find it fascinating that diving birds, such as kingfishers, have eyes adapted to aerial and aquatic vision due to some unique adaptations to the deeper structures of the eye. Water birds and birds that live on open plains have a specialized area in the eye that allows them to fix the horizon accurately as a reference point.
Birds also have brightly colored oil droplets within the eye that are involved with interpretation of color vision. It is thought that the different colored oil droplets enhance contrast by acting as in-the-eye light filters. For example, the yellow oil droplets would remove much of the blue color from the background, which would increase the contrast between an object and the blue sky. The red oil droplet would remove much of the green from the background, which would greatly improve the contrast between an object and trees. The enhanced contrast would considerably increase visual acuity.
Some pet birds seem to have color preferences and aversions. I always try to avoid wearing red when working on pet birds, especially African parrots, including African grey parrots and members of the Poicephalus genus. If anyone walks into a nursery of baby African parrots wearing a bright red shirt, it is almost guaranteed to elicit quite a response from the babies! Adult African greys seem to react badly to red clothing, as well. I find this especially interesting, as the Congo African greys have gorgeous, bright red tail feathers. Red fingernail polish and toenail polish also seem to disconcert some parrots.
Birds are also thought to be able to see light into the near ultraviolet range. This might be why they can identify individual birds that look exactly the same to us, due to the secretions of the uropygial gland that have been spread onto the feathers during preening.
Birds are also known to be able to better detect and follow movement. While a bird and a person might both be able to see a mouse from a height of 250 feet, a person can only do so if his attention was accurately directed to the mouse, but the bird can see it without even directly looking at it. Moreover, the bird is able to see all the mice in a field in a single glance, but we could only do that by scanning the area meticulously. A bird’s vision is truly special and remarkable.