Modification of the visual background increases the conspicuousness of golden-collared manakin displays

Effective visual communication requires signals that are easyto detect, transmit, receive, and discriminate. Animals canincrease the probability that their visual signals would bedetected by evolving signals that contrast with their visualbackground. Animals can further enhance this contrast by behaviorallymodifying the existing visual background. Male golden-collaredmanakins (Manacus vitellinus) clear leaf litter from the groundto form courts, which are used as display arenas. Using reflectancemeasures of the signal (male plumage) and the visual background(cleared court and adjacent litter), the irradiance measuresof ambient light during display, and published measures of photoreceptorsensitivity of a Passerine, we test the hypothesis that court-clearingaugments the contrast between male plumage and the visual background.We find that the chromatic and brightness contrasts of goldenpatches used during courtship are greater against the clearedcourt than against adjacent litter. In addition, we find thatcleared courts provide a less variable background for thesecolor patches, resulting in displays that consistently contrastthe visual background. These results suggest that behavioralmodification of the visual background may act to increase theconspicuousness of colorful male plumage during display, providingan explanation for why golden-collared manakins, and possiblyother species, build or clear display courts.