The two-colour discs had different pairs of colours selected from an orange-to-red spectrum. Female songbirds were trained for the study. They were rewarded if they flipped over a circular paper disc of two colours to reveal food. Researchers could see that the birds could best discriminate between the two colours on the disc. And this new study supports that colour perception may have deeper biological roots than just language and culture. The findings, by a team from Duke University in North Carolina, are published in the journal Nature.