[Heterochronicity in the development of hearing in birds during ontogenesis].

Studies have been made on the development of hearing in the jackdaw Coloeus monedula and sea-gulls Larus canus and L. argenatus, by means of recording microphonic component of the cochlear potential under chronic experimental conditions. Special attention was paid to changes in the regions of maximum sensitivity of the microphonic component during avian growth. It was shown that the range of the perceived frequencies at the beginning of functioning of the auditory analyser coincides completely with the spectrum of parental feeding signals. Threshold parameters of the microphonic component in jackdaw nestlings differ from those of sea-gull embryos by more evident flatness. Narrow bands of the increased sensitivity which are typical of the threshold curves in sea-gull embryos essentially correlated with the chirps of embryos. These data suggest the influence of afferent stimulation on the development of the organ of hearing in birds.