A positive relationship between feeding duration and meal size of avian nectarivores has often been assumed in earlier studies.
We investigated whether feeding duration can be used as a surrogate for the amount of sugar solution ingested by whitebellied
sunbirds, Cinnyris (Nectarinia) talatala. Feeding durations of sunbirds consuming three sucrose concentrations (10%, 20%, and 40% w/w) were measured using an infrared
photodetection system, and the amounts consumed were recorded simultaneously by weighing the feeder throughout the
experiment. For all three diet concentrations, a positive relationship
was found between the time spent feeding per 30 min and the mass consumed. Therefore, feeding duration is demonstrated to be an index of the amount ingested on a particular
sugar concentration. The rate of ingestion, however, depended on the sugar concentration, with the highest rate at the lowest concentration of 10% and the lowest rate at the 40% concentration. Less total time was spent feeding on the 20% solution
than on the 10% solution, but time increased on the 40% diet because of viscosity effects. There appeared to be a weak relationship between feeding patterns and sex, but this was not significant, probably because of interindividual variation.