A large number of coloured sexually selected ornamental traits in the animal kingdom are based on carotenoid and melanin pigments. The biochemical differences between these two classes of pigment, together with their different physiological roles, have led to the general belief that there will be a fundamental difference in the way in which they are used in animal signals. Specifically, it has been argued that carotenoid-based colours will have higher levels of condition dependence and that melanin-based traits will be under tighter genetic control. We present a meta-analysis of studies that have experimentally investigated the signalling quality of the two kinds of colour in birds and show that there is no evidence of a difference between them. Furthermore, we show that the available data are currently very limited, both in the number of studies and in the quality of many of the studies that have attempted to examine this question, and we suggest directions for future work.