Parrots have fluorescent plumage that may be used in mate signaling. A study using mate-choice experiments on budgerigars ("Melopsittacus undulates") found compelling support for fluorescent sexual signaling, with both males and females significantly preferring birds with the fluorescent experimental stimulus. This study suggests that the fluorescent plumage of parrots is not simply a by-product of pigmentation, but instead an adapted sexual signal. Considering the intricacies of the pathways that produce fluorescent pigments, there may be significant costs involved. Therefore, individuals exhibiting strong fluorescence may be honest indicators of high individual quality, since they can deal with the associated costs.