Trapline Foraging by Hermit Hummingbirds: Competition for an Undefended, Renewable Resource

Traplining hummingbirds face a conflict between waiting for undefended floral nectar to accumulate to higher levels of profit and losing accumulated nectar to competitors. The goal of this research was to learn the rules and temporal patterns of flower visitation by Long—tailed Hermit Hummingbirds (Phaethornis superciliosus). Monitors of visits by color—marked individuals, particularly lek males, to natural flowers established patterns of feeding in space and time. Monitors of visits to nectar feeders that were refilled at fixed intervals established patterns of adjustment to nectar availability and competitive losses. Competing hummingbirds tended to segregate among undefended feeding sites, with one individual becoming the primary user of each site. Competition caused hummingbirds to visit a feeder frequently, often before a scheduled refill. In this way one individual could harvest most of the provided nectar. Under conditions of nearly exclusive use of a feeder with artificial nectar, the hummingbirds adjusted their visits to operant (fixed—interval) schedules of food presentation. The scheduled harvesting of floral nectar by traplining hermit hummingbirds thus entails the adaptive use of short, elapsed time intervals.