Biomechanics of the peafowl’s crest reveals frequencies tuned to social displays

Feathers can act as vibrotactile sensors of mechanical stimuli during avian flight and tactile navigation, suggesting they may also detect stimuli during social displays. Here we present the first measurements of the biomechanical properties of bird feather head crests. We show that in Indian peafowl (Pavo cristatus), crest feathers are coupled to mechanosensory filoplume feathers. We also determined that peafowl crests are driven at resonance by their main social display frequency, but that other peacock feathers and crest of other birds have resonant frequencies that vary over a wide range (seven times that of the peafowl's crest). Peafowl crests were also driven to vibrate near resonance when we played back audio recordings of their displays in geometries that mimicked the acoustic near-field geometry found during these behaviors in vivo, but not when we played back control audio. These results suggest that mechanosensory stimuli could complement acoustic and visual perception and/or proprioception of social displays in peafowl and other bird species.