Vigilance behavior of a tropical bird in response to indirect and direct cues of predation risk

Abstract

AbstractAnimals use a variety of cues to evaluate their risk of predation when foraging, including direct cues of predator presence such as vocalizations or scent, and indirect cues, or environmental correlates of predation risk, such as vegetation structure. Research took place in a large-scale forest restoration experiment where habitat patches of different sizes were planted. I examined the effects of predator vocalizations (direct cues) on the vigilance behavior of Cherrie's Tanagers (Ramphocelus costaricensis) foraging in three different locations with varying amounts of vegetation cover (indirect cues): small patches and the centers and edges of large patches. Results show that the indirect cue of predation risk mediated birds' response to the direct cue. The increase in time birds spent alert in response to the predator call was significantly greater in the presumably riskier small patches and large patch edges compared to the relatively safe large patch centers. The increase in frequency of head-turns also was significantly greater in small patches compared to the large patch centers in response to the predator call. Although birds recognized the threat of the predator call and reacted by fleeing more quickly than after the non-predator call, this response did not differ between locations. Birds appeared to integrate information from both types of cues to evaluate their predation risk and determine their vigilance response. Individuals responded more strongly to the direct cue of predation risk when foraging in the presumably riskier smaller patches and large patch edges by increasing vigilance. These results highlight the importance of investigating behavioral responses to the characteristics of forest restoration sites, many of which consist of small patches of habitat.