Energy Intake and Expenditures in a Nectar‐feeding Sunbird
1975
Wolf, Larry L.
A series of 2— to 3—h observations of two breeding male Malachite Sunbirds (Nectarinia famosa) territorial at Aloe graminicola flowers was made in the highlands of Kenya. Average time budgeting, and hence energy budgeting, varied little between males, but each male showed significant differences in time and energy budgeting with stage of the nesting cycle. Empirical regression equations were used to estimate the total energy intake from nectar and the average caloric intake per flower visited per observation period. Male 1 generally took in more energy from nectar than it spent during an observation period; Male 2 regularly took in somewhat less energy than it expended. Both males probably supplemented energy intake from nectar with energy from insects. Multiple regression analyses supported the idea that the percentage of time a male spent foraging was primarily a function of (1) the amount of energy obtained per flower on the average during the observation period, and (2) the amount of time and hence of energy that was spent in chasing other birds from the nectar sources being defended and from the vicinity of the female while she was nest—building. There was no relation between percent time foraging and (1) the ambient temperatures during the observation period, or (2) the amount of time spent in flight activities other than chases. It is suggested that these males made relatively short—term adjustments in their foraging time as a function of energy intake and to some extent expenditure. However, the relation of foraging time to chase time may reflect also the impact of introducers on the energy content of the territory of the male.
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