We often think that other animals see the world the same as us, but birds see the world differently. Birds eyes are different from ours, and this changes how they perceive the world.
Birds see colour and see more of the colour spectrum than most mammals. Birds have a fourth cone in their eyes which allows them to see ultraviolet. This allows birds to find food, avoid predators, mate, and navigate.
Vision is the most highly developed and acute sense among birds, and they have a keen sense of colour. Understanding how birds see gives us a better view of how they view the world.
What Colours Do Birds See?
Birds see many different colours than humans. We can see red, blue, and green, and colours and shades made up of these. Birds, however, can see all these and parts of the ultraviolet (UV) spectrum that we can’t see. Birds are known as tetrachromats.
Bird vision is also sharper than humans. Birds can distinguish minor differences between similar shades, so they can see colours that we can’t. Birds generally have four cones in their eyes instead of three like humans, and they perceive colour differently. Not all birds have four cones, but birds typically have more cones than humans and other mammals in their retinas.
Each cone in the retina has a drop of oil in it. This oil filter allows the bird to see different shades as it filters out different colours. This works the same as the popular camera or Instagram filters.
The oil can be transparent, pale, red, or yellow, giving them greater contrast. These help birds filter out the colours of leaves, bushes, and trees, allowing them to find their prey. The filters also help birds that catch fish, allowing them to find fish in deep water. Mammals, including ourselves, do not have this oil in their eyes.
Eagles see through a yellow filter from the oil. The yellow oil allows them to see subtle and slight shifts in their vision, such as a vole in the distance, easier as it shows the outlines clearer.
Humans can see one nonspectral colour. We can see purple when our blue and red cones are stimulated. Scientists believe that birds can see up to five colours: purple, ultraviolet and purple, ultraviolet and green, ultraviolet and red, and ultraviolet and yellow.
Using a series of experiments, scientists found that hummingbirds can recognize a variety of nonspectral colours. These include purple, ultraviolet and green, ultraviolet and red, and ultraviolet and yellow.
Nocturnal birds see colours better
Birds with the best colour sense are birds that are active during the day. This is because diurnal birds need more ways to filter out colours than nocturnal birds.
As with other nocturnal mammals, nocturnal birds can see better at night due to having more rods in their eyes. Although these do not help them see colour, they allow them to see better in low light.
Unlike humans, birds can see ultraviolet light spectrums. Seeing in UV allows birds a different perception of the world and helps them survive in the wild.
Recognising food through colour
Many birds survive on a diet of fruits and berries, and their ultraviolet eyesight helps them. Seeing in ultraviolet allows the birds to see berries and fruits against bushes and trees as they reflect UV light. While humans only see different red, blue, and green shades, birds see many more shades, with leaves being darker underneath and lighter on top.
Their colour vision can also stop them from eating poisonous plants. Many toxic plants are brightly coloured, which birds can spot quickly and easily.
Hummingbirds feed on the nectar from flowers, and there is evidence seeing ultraviolet aids them in finding flowers with the most nectar.
Although many small mammals will try to hide in bushes or under stones when they spot a predator such as an eagle, they don’t realize predators can see their trails and urine in ultraviolet.
Finding a mate
Male and female birds of many species look similar when viewed by ourselves, but the ultraviolet spectrum shows differences in their feathers and plumage. Because birds can see in ultraviolet, they can immediately tell the male and female, allowing them to find a mate easily.
Helps them navigate
The sun is probably the best-known source of ultraviolet rays. Although we cannot see the ultraviolet light, we do feel the effect of it. Ultraviolet light can penetrate thin cloud cover. This allows birds to find the position of the sun, which helps them in navigating.
Choosing the correct eggs
For years, ornithologists and scientists could not distinguish how birds can tell their eggs from other eggs, but this comes down to their extended vision. Patterns that show up only in ultraviolet allow the parents to find the correct eggs, even when others look alike.
Helps them migrate
Although not the only reason for knowing when to migrate, the colour of the foliage helps the birds know that the seasons are changing and that it will soon be time to move to a warmer climate.
Birds can see in colour and different spectrums to ourselves. As we can see, it helps them survive in many ways. Their colour vision helps them find a mate, see which eggs are theirs, and find food, while also helping their migration and navigation.