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Fruits are among the most antioxidant‐rich foods in nature and thus can be important dietary sources for combating oxidative stress in animals and humans.

Because fruits are pigmented by important plant antioxidants such as anthocyanins and carotenoids, frugivores may be able to gauge the antioxidant value of a fruit by its colour. However, although the importance of dietary antioxidants and oxidative stress is increasingly being acknowledged in evolutionary ecology, it is unknown whether animals can use visual signals to detect the presence of antioxidants in their food.

We studied the colour and pigment content of 60 bird‐dispersed fruits and used an avian eye model to assess the ability of birds to visually discriminate carotenoid and anthocyanin contents of fruits. We then tested whether the frugivorous European blackcap (Sylvia atricapilla) preferentially consumes food containing anthocyanins.