Differential response variability of black-capped chickadees to wingbeat sounds and vocalizations

Prey species use various cues (visual, acoustic, olfactory) to detect approaching predators. Among these, visual cues are generally considered reliable, providing immediate and accurate information about potential dangers. While acoustic cues also play a key role in threat assessment in birds, the relative importance of different auditory cues and their integration are less well studied. Here, we investigated how black-capped chickadees (Poecile atricapillus) respond to predator and non-predator wingbeats and vocalizations presented independently and in sequence with each other. In an exploratory playback experiment with 16 chickadees, we found no differences in how chickadees responded to predator versus non-predator acoustic cues when presented individually or sequentially. However, sequential presentations of acoustic cues had reduced response variance compared to solo playbacks. These findings suggest that black-capped chickadees may lack specific recognition mechanisms for discriminating predator from non-predator wingbeats in isolation but may integrate multiple cues to improve threat assessment reliability. Our results demonstrate the potential role of non-vocal cues in acoustic threat assessment in small passerines and the importance of considering within-modality cue integration in anti-predator behaviour studies. Future behavioural study designs would benefit from incorporating the current findings.