We studied the home-range size and activity patterns of brown long-tongued bats Glossophaga commissarisi (Phyllostomidae) in the lowland rainforest of Costa Rica and related this to local nectar and fruit resource distribution. Home ranges were determined using radiotelemetry and food plants within were mapped. Within home ranges of 12.5 ± 6.7 ha, G. commissarisi used mainly small foraging areas of 3.0 ± 1.0 ha. Spatial use within foraging areas correlated for most bats with nectar and fruit resource density. Flight time and duration of flight phases were significantly lower for individuals feeding in a clearing with high abundance of nectar resources compared with those feeding in secondary rainforest with a lower nectar resource density. Our results indicate that G. commissarisi closely matches its flight activity to the available resource distribution.