[Development of species specific acoustic sensitivity in hole-nester fledgelings]

A study was made of acoustic sensibility of hole nestlings to species-specific signals of adult birds. It has been established that the final formation of sensibility to such signals is not completed in the embrional period of development, but continues, at least during the first half of life in the nest. In the embrional period, the formation of sensibility is concluded only within the spectrum of the "alimentary" signal complex, providing for adequate alimentary behaviour of the nestlings immediately after hatching. In the early postembrional period, the formation of acoustic sensibility in the spectrum of other species-specific signals (alarm signals) is completed in parallel with the organization of behavioral reactions controlled by these stimuli.