Feeding territories of Golden—winged Sunbirds contain enough energy to support an individual's daily energy requirements, and the amount of nectar per flower inside a territory tends to average higher than in adjacent undefended flowers. When undefended nectar levels are low (especially below 2 @ml per flower) the costs of territorial defense can easily be offset by energy saved from shortened foraging time budgets made possible by feeding at the higher average nectar levels. At higher undefended nectar levels the costs of territorial defense should no be recoverable. The balance between these costs and gains appears to define the conditions when territorial defense in this species is advantageous.