Sugar-type preferences of nectarivores may be an important selective factor in the evolution of sugar composition in floral nectar. We investigated sugar preferences of the Malachite Sunbird (Nectarinia famosa), using experiments in which birds were offered paired choices between energetically equivalent solutions over a range of sugar concentrations. The birds preferred hexose at low (5%) concentration and sucrose at high (25%) concentration; they showed no preference at 10%, 15%, and 20% concentrations. The birds regulated energy intake by adjusting volumetric consumption, except on a 5% concentration diet, where they failed to maintain energy balance. They also exhibited a strong preference for concentrated solutions, given a choice between 10%, 15%, 20%, and 25% sucrose solutions. We discuss the significance of these results in terms of the nectar composition of sunbird-pollinated plants.