ABSTRACT
Feathers act as vibrotactile sensors that can detect mechanical stimuli during avian flight and tactile navigation, suggesting that they may also detect signals during social displays. We explored this potential novel sensory modality by studying the biomechanical properties of feather crests that are found on the heads of Indian peafowl (Pavo cristatus). We show that these crest feathers are coupled to filoplumes, small feathers known to function as mechanosensors. We also determined whether the airborne stimuli generated by peafowl courtship and social displays couple efficiently via resonance to the vibrational response of feather crests. Vibrational measurements showed that peafowl crests have fundamental resonant frequencies that could be driven near-optimally by the shaking frequencies used by peacocks performing train-rattling displays. Crests were also driven to vibrate near resonance when we played back mechanical sounds generated by these displays in the acoustic very near-field, where such displays are experienced in vivo. When peacock wing-shaking courtship behaviour was simulated in the laboratory, the resulting pulsatile airflow excited measurable vibrations of crest feathers. These results suggest that peafowl crests have properties that make them suitable mechanosensors for airborne stimuli generated during social displays. Such stimuli could complement acoustic and visual perception, thereby enhancing the detection and interpretation of social displays. Diverse feather crests are found in many bird species that perform similar displays, suggesting that this proposed sensory modality may be widespread. We suggest behavioral studies to explore these ideas and their functional implications.
Summary statement Peafowl crest feathers have mechanical properties that make them suitable for sensing potential airborne signals generated during multimodal social displays.