Movement Strategies of Neotropical Nectarivorous Birds: Insights From High-Andean Hummingbirds and Flowerpiercers

Tropical nectarivorous birds should have flexible movement behaviors in response to the spatiotemporal availability of flowers. In the Neotropics, hummingbirds (Trochilidae) have diet breadths constrained by trait-matching with flowers, while nectar-robbing flowerpiercers (Thraupidae) typically drink nectar from holes pierced at the flower's base. Distinct movement patterns for these two bird families would be expected from optimal foraging theory due to differences in dietary specialization and behavioral flexibility, yet little is known about the daily movement patterns of tropical nectarivores. We used fine-resolution tracking data from an automated radio telemetry grid to compare movement patterns between hummingbirds and flowerpiercers in high-Andean mountain ecosystems, and obtained an accumulated total of 435,513 location estimates and 452 tracking days from 22 individuals across six bird species. Our results indicate that hummingbirds exhibit a greater diversity of movement behaviors compared to flowerpiercers, with varying space use and recursion patterns that are characteristic of sedentary, commuting/traplining and exploratory strategies, whereas most species of flowerpiercers were classified as central-place foragers. However, there is substantial variation in daily movement metrics and hierarchical clustering does not necessarily group together bird families, species, nor even individuals as more similar to each other. Flexibility in movement behaviors has seldom been described for neotropical nectarivorous birds in the wild. It emerges as an important trait to adjust behavior to variable local contexts, and may be adaptive for the persistence of pollinators in challenging mountain ecosystems, where weather conditions are harsh and floral resources are seasonal.