The Effect of Periodical Cicadas on Food Web Dynamics

<p style="font-weight: 400;">Arthropods play critical roles in food webs as both consumers and prey for higher trophic levels, including birds. Every 13 or 17 years, millions of periodical cicadas (<em>Magicicada spp</em>.) emerge from the ground and create a significant biomass pulse that disrupts food web dynamics. Little research has been conducted in North Carolina on the indirect effects that periodical cicadas can have on food web dynamics, and this study aims to bridge that gap by examining their impact. We predicted that the emergence of periodical cicadas would alter bird predation on caterpillars and vary across an urbanization gradient. We deployed clay caterpillar models to assess bird predation at five different study sites throughout the summer, surveyed arthropod populations at those five sites, and performed data analysis to assess whether periodical cicadas had an indirect positive effect on caterpillar populations. We found that caterpillar abundance increased significantly during the cicada emergence, indicating a shift in bird predation from caterpillars to cicadas, but the magnitude of the effect varied across sites and was best explained by our estimates of site-level cicada density. While we observed a marginal positive relationship between urbanization and caterpillar abundance (p=0.056), this pattern is a secondary driver in the changes in caterpillar density. These findings contribute to a deeper understanding of how resource pulses, such as periodical cicada emergences, can significantly alter food web dynamics. While our findings suggest a potential link between urbanization and changes in caterpillar abundance, further research is needed to confirm these patterns. This study also has broader implications for understanding urbanization&rsquo;s impact on ecosystem functions and its relevance to management strategies targeting invasive species.