Temporal patterns of dominance in a hummingbird assemblage

Abstract

Abstract A substantial gap in dominance hierarchies research is understanding how such relationships change over time. Previous studies have generally used a single interaction matrix, assuming that dominance is temporally consistent. Yet food sources can be scarce and temporary, leading to changes in species frequency and assemblage composition. Hummingbird assemblages fluctuate as these tiny birds track seasonal floral resources, with individual movements affecting species composition. Artificial feeders, which may foster a greater number of aggressive interactions, provide a stable environment for studying dominance, unlike ephemeral and shifting wild resources. To assess the temporal stability of dominance relationships, we documented aggressive interactions in a hummingbird assemblage over three months on the western slope of the eastern Cordillera of Colombian Andes. We tracked local changes in species composition and visit frequency, recording interactions among 11 hummingbird species using high-speed cameras at three time scales: hour, day, and month. Dominance relationships and their certainty were analyzed through Perc analyses and interaction networks. Over three months of recording, and perusing over 27 hours of non continuous highspeed videos, we registered 3,907 aggressive interactions and 12,629 visits. Our results revealed substantial temporal variation in dominance relationships, species composition, and visit frequency, even within the constant food source that feeders provide. Dominance hierarchies were generally intransitive, with large species dominating, but also with smaller species occasionally winning interactions. We found high uncertainty in dominance relationships within shorter intervals with fewer interactions ( e.g ., hourly); and that rank changes between dominant species across months and days were linked to shifts in feeder visits. We recommend that future studies incorporate temporal variation, certainty analyses, and interaction networks to determine whether dominance relationships are stable enough to form reliable hierarchies and to explore the ecological significance of reversals in dominance and associated determinants. Highlights Dominance fluctuates across temporal scales, with monthly, daily, and hourly variations. Hierarchies become less stable at finer temporal scales. Body size and feeder visitation frequency shape dominance interactions. Smaller species initiate more aggressive interactions but lose more frequently. Relationships among dominant species are less predictable than among subordinates.

Affiliated Institutions

• Universidad Nacional de Colombia CO
• University of Washington US
• Colibrí Gorriazul Research Center
• Burke Museum of Natural History and Culture US
• Colibri (Netherlands) NL

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