Mobbing is an important anti-predator strategy where prey will approach, harass, and sometimes even attack a predator to drive it from an area, and is an important anti-predator strategy for many species. In terrestrial systems, especially in birds, mobbing is accompanied by calls that contain detailed information about predatory threat and typically serve to recruit other individuals sharing the same threat. Research shows that both conspecifics and heterospecifics recognize these calls and decode their information content; this multi-species communication is hypothesized to create large community-wide anti-predator communication networks. However, although thought to be important to communities, communication networks remain poorly described and understood. How individual species respond to one another’s calls in a large species community, for example, has been largely unstudied.
Our objective was to determine how different species interact with one another in the context of mobbing events. More specifically, determining if relationships between species are (1) generally uniform (i.e. all species respond equally to one another’s mobbing calls), or (2) are species-specific (i.e. each species has its own likelihood of response based on the identity of the species starting the mobbing event). To answer this question, we experimentally instigated mobbing events by broadcasting mobbing calls recorded from each of the six species of passerines that participate in mobbing events regularly. We then recorded the responses by all responding species to determine how birds respond to one another in the wild.  We found that while some species appear to respond more generally to mobbing events, others are more species specific in their responses. Additionally, species made decisions about whether to assist in mobbing based not only which species instigated a mobbing event, but also how many conspecifics were present and which season it was (spring breeding season vs. winter mixed-species flocking season).
We hope that by better understanding the relationships between the species engaging in these communication networks, we will better understand how information about predators is produced, spread, and used in these communities. We also hope that this will be the first step to allowing us to ask questions about how changes in species ecology and environment may impact these networks.