If competition among bird-pollinated flowers favours the evolution of readily discriminated colour signals, the signature of pollinator-driven adaptation should include not only floral colour differences between insect- and bird-pollinated flowers,
but also fine tuning of colour signals within a syndrome to those wavelengths of radiation that the preferred floral visitor can
most easily distinguish. We tested this hypothesis using quantitative metrics of the match between floral colour cues and the visual capacities of hymenopteran insects and of birds.