High frequency components in avian vocalizations

Ultrasonic communication in vertebrates is attracting increasing research interest. To determine if ultrasonic vocalization is common in birds, we recorded their vocalizations with ultrasound detectors in the Dongzhai National Nature Reserve of Henan Province, China. We found varying degrees of high frequency components in the vocalizations of 14 species and in several of these species, the frequency of harmonics was up to the range of ultrasound. We suggest that more studies are required to determine whether the high frequency components in avian vocalizations have functions and what these functions are. In addition, the ability of birds to hear sounds in the high frequency range also requires re-examination.