Unlearned preference for red may facilitate recognition of palatable food in young omnivorous birds

Abstract

Unlearned colour choices by consumers are generally interpreted as an adaptation to avoid unprofitable prey, often involving red warning coloration. However, red colour is a context-dependent stimulus. It signals palatability in ripe fruits, but unlearned fruit colour preferences have rarely been assessed. Therefore, we tested unlearned preferences and the effect of experience on differently coloured artificial fruits in an omnivorous bird. Naïve hand-raised blackcaps (Sylvia atricapilla) preferred red to blue, green, yellow and white artificial fruits, while adult wild-caught birds had no colour preference. In the area from which the experimental birds originated, red ripe fruits are present in 53 % of the species with fleshy fruit displays in summer. In these circumstances, unlearned preferences for red might facilitate food recognition in inexperienced fruit-eating birds. Unlearned colour choices should thus be interpreted in a broader context of foraging and not only to explain warning coloration. The contrasting choices of adult and naïve birds imply, however, a low potential for directional selective pressures on fruit colour evolution in this system.