Predators not only impact prey populations directly by consuming individuals, but also indirectly by altering prey behavior. These non-consumptive effects elicit changes in important activities, for example causing animals to allocate more time to vigilance behavior and less time to foraging. When individuals alter behavior to avoid predation, the amount of risk that an animal perceives in its environment, or perception of ambient predation risk, can have important implications for individual fitness and population-level processes. Additionally, habitat structure, such as vegetation height and density, can impact the ability of animals to detect and hide from predators, and therefore influence their perception of predation risk. Along these lines, my objective for this study was to determine if vegetation structure influences the perception of ambient predation risk in a wild bird species. I tested this relationship by measuring the predator mobbing behavior of Florida Scrub-jays (Aphelocoma coerulescens) presented with a mounted Cooper's Hawk (Accipiter copperii).
Results/Conclusions
Using redundancy analysis (RDA) for multivariate analysis and generalized linear models for measures of mobbing behavior individually, I found a relationship between vegetation structure and mobbing intensity. Specifically, I observed increased mobbing intensity (duration, vocalizations, and approach distance) in more overgrown scrub, which may suggest higher perception of ambient predation risk in these habitats, as Florida Scrub-jays may have a greater incentive to drive the hawk away because their usual predator detection behaviors are compromised in these habitats. Conversely, reduced mobbing duration in younger stands with tall perches available suggests reduced perception of ambient predation risk, as Florida Scrub-jays may be able to stay farther away and observe the predator. The potential for increased perception of predation risk in certain habitats is significant in FSJs because any changes to vital behaviors could have negative impacts on small and isolated populations of this threatened species.