Vigilance behaviors of Ruby-throated Hummingbirds (Archilochus colubris) reflect elevated risk of competitive interactions with vespine wasps

Abstract

Interactions between hummingbirds and potentially dangerous or aggressive insects at shared food sources may result in interference competition and risk-avoidance behaviors. To examine the potential interplay between perceived risk and interference competition, we observed the vigilance behaviors of Ruby-throated Hummingbirds (Archilochus colubris) foraging at artificial feeders with and without visual obstruction in the presence and absence of 3 species of wasp (Hymenoptera: Vespidae: Vespinae). Hummingbirds withdrew their bills from the visually obstructed feeder more rapidly than when feeding with a clear view of the surroundings. Wasps caused hummingbirds to spend a greater proportion of their visit vigilant, an effect positively correlated with the number of wasps at the feeding station. Aggressive competitive interactions at feeders were asymmetric. Hummingbirds avoided feeders with wasps and switched between available feeders more often and were never observed pursuing wasps away from the feeder. Instead, hummingbirds were chased by wasps or avoided foraging from feeders when wasps were present. Changes in hummingbird vigilance patterns in response to wasp aggression match those of other avian species whose antipredator vigilance patterns have been thoroughly examined. Thus, although interference competition inevitably occurs, vigilance patterns suggest that hummingbirds do perceive wasps as a potential threat and not solely as competitors.