Evaluation of the visual signal in playback by territorial responses of nuthatches

A playback experiment is a well-established method for behavior research, especially in the study of the territorial responses of songbirds. Birds obtain information from multimodal signals, whereas only acoustic signals are provided in traditional playbacks. Many efforts have been made to combine visual signals with playback experiments, e.g., static specimens, videos, live birds and robotic models. Multimodal signal playback provides an elaborate way to study the behavior of focal birds. Although combining visual signals with playback experiments can elicit more authentic responses, empirical evidence remains scarce. In this study, a robot model mimicking a territory intruder was presented to Eurasian Nuthatch ( Sitta europaea ) to evaluate its effect on playback experiments. The experiments were conducted on 45 individuals during the 2021 breeding season in Baihua Mountain National Nature Reserve (39°83ʹ N, 115°58ʹ E), China. These 45 individuals were randomly divided into three equal-sized groups corresponding to the experimental treatments: playback sound only; sound with a static model; and sound with a dynamic model. Behavioral variables were recorded during each experiment to generate response intensity via principal component analysis. The results revealed that there was no significant difference in response intensity among the three different experimental treatments. Considering the dense habitat where nuthatches live, the robot model may have insufficiently increased the stimulation of sensory perception. We propose that the effect of visual signals during playback should be evaluated in more species and that behavioral studies could be conducted using multimodal signals to provide a more realistic representation of bird‒bird interactions. • This study used a robot that mimicked a territory intruder and played sound to examine the impact of multimodal signals on Eurasian Nuthatches (Sitta europaea). • No notable difference in nuthatch responses was found between sound-only and multimodal signal playbacks. • The findings were explained considering the birds' sensory abilities and environmental factors.