How can a little bird scare off a predator that is considering its next meal? Sometimes it can recruit a team of small but collectively mighty defenders capable of scaring off the intruder through aggressive vocal and physical pestering, a behavior known as mobbing.
Bird mobbing often starts with anti-predator vocalizations, those distress, flee/freeze, recruitment, and alert calls that some species make to communicate with other adults or nestlings. In the presence of a predator, those calls can be incorporated into mobbing calls to induce mobbing behavior – scolding and physically attacking the predator. Researchers are studying these calls, including whether specific sequences of notes are required to elicit mobbing, how the calls from one species motivate another species, how mobbing responses change during the nesting season, and how urbanization decreases mobbing responses.
This noise making and body-slamming is risky behavior since calling attention to oneself, flying close to a predator, and leaving the nest unprotected can have consequences. It makes sense that the benefits of mobbing must outweigh the risks, but little research has been done to measure those trade-offs.
Check this YouTube video of mobbing behavior or this Macaulay Library recording of agitated Black-capped Chickadees to see and hear these harassing behaviors.