The size of male adornments in the scarlet-tufted malachite sunbird varies with environmental conditions. On Mount Kenya they feed almost exclusively on the nectar of Lobelia telekii flowers.
Males are bright iridescent green, with red pectoral tufts and elongated central tail feathers.
The pectoral tufts and the tails of males measured in both 1989 and 1990 increased between years. This increase could be due to an age effect on these characters or to differences in condition of the males in the two years. There was an increase in the population tail length and pectoral tuft size of the same magnitude as the change seen in known males which suggests that an age effect is unlikely. The density of L. telekii inflorescences increased between the two years, so more food was available in 1990 than in 1989. Weather records and data from breeding success also suggest that conditions in 1989 were harsher than in 1990.