Postnatal hearing development limits early parent-to-offspring vocal communication and gates sensorimotor learning in the zebra finch

Abstract

Hearing is critical for vocal communication, and in birds its onset is linked to egg hatching. Hearing develops after hatching in early hatching (altricial) species, while already functional in the egg in later hatching (precocial) species. Recent work suggests that altricial zebra finches exhibit parent-to-embryo acoustic communication, requiring functional, high-frequency hearing already in the egg. Yet, the early postnatal development of their auditory sensitivity remains unknown. By measuring hearing and vibration-detection capacity during postnatal development in zebra finches, we show that zebra finch hatchlings are deaf even to loud, broadband sounds. Auditory nerve sensitivity develops gradually in a low-to-high frequency manner. Auditory nerve responses show adult-like properties only after 20 days from hatching. Our data provide evidence against the plausibility of early parent-to-offspring acoustic communication in zebra finches and suggest that hearing functionality may set the onset of vocal learning in zebra finches.