The Influence of Nectar Concentration and Time of Day upon Energy Intake and Expenditure by the Singing Honeyeater, Meliphaga virescens

Abstract

Meliphaga virescens drinks nectar at a greater rate in the morning and at midday than later in the afternoon. This trend is due primarily to similar variations in the time spent drinking rather than changes in the rate of licking or frequency of visits to the nectar source. A progressive reduction in the amount of time spent flying throughout the day results in birds being able to accumulate excess energy at a relatively uniform rate. It has been suggested that this strategy helps birds in their attempt to stabilize body weights. When birds are switched from a 0.8 M to a 0.4 M nectar regime, they increase the rate of fluid intake and decrease the time spent flying. Compensation for calorific dilution is incomplete for birds switched to 0.4 M nectar in that the birds are unable to accumulate the same daily quantities of excess energy as before. This is probably the major reason for their apparent inability to stabilize morning and evening body weights.