In almost any lighting conditions, colour vision is crucial for chickens in order to find good food that is ripe to eat and to identify high quality partners to mate with, according to a new study which found the bird - just like people - has colour constancy.
For birds, this means that they, in different environments and under different lighting conditions, recognise the colour of, for instance, berries and can thereby distinguish those that are ripe from those that are not, researchers from Lund University in Sweden said.
Without colour constancy, they would not be able to rely on their colour vision - they would simply see the berries in different colours as the light changed. They would certainly also not be able to recognise their own kind of species, they said.
The results were achieved by researchers from training chickens. Initially, the chickens were kept in an environment with white light and had access to containers marked in three different colours: red, yellow and orange.
Only by selecting the orange container would the birds receive food. Researchers then studied which container the chickens selected when the light in the room was switched to different shades of red.
The results showed that the chickens continued to select the orange container, researchers said.
"We studied many different lighting conditions to find out how big the changes in light could be without the chickens losing their colour constancy. This type of study has never been done before," said Peter Olsson from Lund University.
By using a mathematical model, researchers calculated how big the changes in light are inside the chickens' eyes.
The same model can be used on other animals and thereby allowed researchers for the first time to compare the colour constancy of chickens and birds to the colour constancy ability in other animals.
"We can also compare the chickens' colour constancy ability in the laboratory to the light changes they and other birds experience in nature, such as how the lighting conditions differ in the woods from in an open field," said Olsson.
"Our results show that they are able to maintain their colour constancy under greater changes in light in the laboratory than when experiencing those that occur in nature," he said.
Researchers established that chickens - just like people - have colour constancy.
The findings were published in the journal Proceedings of the Royal Society B.
