Perception of predation risk in tropical dry forest birds in central Mexico

Individuals are expected to balance the costs and benefits of their escape decisions based on aspects of their biological condition and life history, for example, size, body mass or satiation level. Flight initiation distance (FID) is the distance at which animals escape when approached by humans, under standardized conditions. It is used as a proxy of animals´ perception of predation risk. Escape behavior is a proxy to measure anti-predator strategies and to monitor tolerance and human impacts on birds. This study analyzes the perception of predation risk in bird species within a tropical dry forest with continuous human presence. Our experiment evaluates the influence of body mass, activity, and residence status on the perceived predation risk based on FID. We predicted longer FID in larger than in smaller bird species (based on body mass), in perching birds relative to foraging individuals, and in migratory relative to resident species. The values of FID in 19 species (82% residents) during 76 trials ranged from 2.46 to 32.29 m. There was a quadratic relationship with size, in which birds with intermediate size had longer FID than lighter or heavier species. Perching individuals had longer FID than foraging individuals. FIDs were similar between resident and migratory birds. Behavioral mechanisms and life history of particular species may explain differences in escape strategies.