The day and night visual capacities (photopic and scotopic spectral sensitivity) of several species of boobies (family Sulidae) were analyzed using a behavioral psychophysical testing technique. On the basis of these data there is evidence for sensitivity to near-ultraviolet light in the order Pelecaniformes. The scotopic spectral sensitivity functions of three booby species conform closely to the spectral absorption characteristics of avian rhodopsin. There are marked differences between the photopic sensitivities of a coastal booby species with that of a pelagic species; these differences appear correlated with their respective feeding ecologies. Lastly, a brief review of avian spectral sensitivity and a consideration of individual variation in avian vision studies are presented.