The Silence Of Prey: Hummingbirds Do Not Respond To Potential Ambush Predators On Flowers

Predation is one of the most important ecological factors determining the structure and functioning of ecosystems. Among the various strategies used by predators to obtain food, there are those in which they take advantage of the vulnerability of the prey during its foraging bouts. An unexplored example of this strategy is the interaction between vertebrate pollinators and ambush predators. Despite the reports of arboreal tarantulas preying on hummingbirds, little is known about the behaviour of these birds in the presence of their predators. Thus, our study sought to investigate hummingbird behaviour against potential opportunist predators during their search for food resources. We used Heliconia velloziana as a mutualist model, in which, we separated plant flowers in two groups - plants with predators and plants without predators - in order to observe the behaviour of pollinators during their foraging activity. The rate of visitation was also indirectly estimated based on residual nectar and pollen. Our results show that hummingbirds initially avoided contact with the predator, but later they visited both groups indiscriminately. The results suggest that these birds do not have counter-adaptations to identify invertebrate ambush predators as a threat. Since such predators are generalists and the events of predation are sporadic, they do not exert selective pressures strong enough to lead to the development of evasive behaviours. We conclude that hummingbirds are potential prey for opportunistic ambush predators.