A first approximation of the energetics of Cape sugarbirds (Promerops cafer) and orange-breasted sunbirds (Nectarinia violacea)
Estimated expenditures by Nectarinia violacea and Promerops cafer vary throughout the day, with highest rates occurring during the morning when nectar availability is greatest. Energy storage needed to satisfy overnight requirements by these nectarivores probably occurs only during the morning, with deficits being incurred at other times, although the ingestion of insects may help to reduce these deficits. Male and female P. cafer are frequently territorial, showing a clear preference for foraging at partially opened inflorescences of Mimetes hirtus. Smaller male N. violacea are usually excluded from M. hirtus and obliged to forage on less rewarding Erica perspicua.