When it comes to picking fruit, tropical Asian birds seem to favour red and black fruits according to an investigation published in Scientific Reports. These are the most common colours of fruits that are chiefly dispersed by birds; thus, the observations suggest that fruit colours have evolved, to some extent, to attract birds.
Rui-Chang Quan and colleagues evaluated the preferences of four species of fruit-eating birds from southern China for artificial and natural ripe fruit of five different colours. Artificial fruits were made from a mixture of apple, pear, banana, wheat and corn flour, and were dyed black, red, yellow, green or blue, matching the colours of the natural ripe fruits used. They found that both wild-caught and hand-reared birds had a consistent and strong preference for black and/or red colours, which are most common in the region, and avoid the uncommon colours, such as artificially and naturally green fruits.
The authors note that compared with other colours, red and black fruits stand out the most against the background used in the experiments, and acknowledge that contrast as well as colour may have influenced their results. However, their findings support the hypothesis that black and red fruits are common because, in part, fruit-eating birds prefer these colours.