Although red and black are the fruits dispersed chiefly by birds, it is still contentious as to whether the frequency of fruit colours, especially black and red, in the wild match the colour preferences of bird consumers.

Tropical Asia is an ideal location for expanding knowledge of the colour preferences of birds because tropical Asia has the largest diversity of frugivorous bird species in the world. However, very few studies have been conducted in this region.

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences (CAS) experimentally addressed several questions concerning the preferences of frugivorous birds in Xishuangbanna. They hypothesized: (1) black and red fleshy fruits would be preferred by hand-raised birds, as well as wild-caught ones. (2) colour preferences of naive birds would be closest to the frequency of fruit colour in the wild. (3) colour preferences of both experienced and naive birds were constant over time

They used artificial fruits, fresh fruits, four wild-caught resident frugivorous bird species, and hand-raised naive birds from three of the same species. 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. The birds were representative of two important families of Asian frugivores (bulbuls and barbets). They used the following colours on artificial and natural fruit: black, blue, green, red and yellow.

They demonstrated that all experimental birds had a strong preference for the most common fruit colours, black and red. Relative to adult wild-caught birds, the innate colour preference of hand-raised birds, with a strong preference for black natural fruit, better reflected the frequency of natural fruit colour in Xishuangbanna. The preferences for common-coloured fruit and avoidance of ripe fruit of an uncommon colour were relatively invariant at inter- and intra-specific levels, and were also stable over time.

The study entitled “Bird fruit preferences match the frequency of fruit colours in tropical Asia” has been published in Scientific Reports.