Predator-risk-sensitive foraging behavior of Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) in response to the head orientation of snake predator models

Abstract

The risk of predation varies with behavioral cues and body characteristics of potential predators. One such body characteristic is the head/face orientation of the predator. However, a prey individual’s ability to detect the head may be more difficult when the predator’s body is serpentine, with little distinguishing the head from the tail. Here, we tested whether individuals in mixed-species flocks of Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) distinguish the head orientation of predator snake models. We conducted behavioral observations at multiple sites each having a bird feeder stocked with seed. Each chickadee and titmouse flock was exposed to two counterbalanced trials: a snake model with head closest to the seed area of the feeder and with tail closest to the seed area of the feeder. Observers recorded the number of seeds taken by each species and also the number of unsuccessful feeder visits. Chickadees and, to a lesser extent, titmice took fewer seeds and had more unsuccessful feeder visits when the head of the snake model was closest to the seed, compared to when the tail was closest to the seed. Titmice, furthermore, had more unsuccessful feeder visits to the black snake model type representing a real snake nest predator for these small songbirds. Therefore, head orientation seems an important factor that some species use to assess predation risk, even for predatory species where head orientation may be a subtle cue.