Early natural feeding behavior of the young is characterized by an apparent cyclic organization: feeding response or active begging with later shift in the nest is followed by the resting phase – short sleep or calm wakefulness. Cycle duration varies with age from 40-50 min in younger nestlings to 18-23 min in the older ones. The wavelet power spectrum was analyzed based on the wavelet transformation of the complex Morlet basic wavelet (ω0=2π) in the range 0-20 Hz. Within the feeding cycle the following functional states were selected: day sleep, passive wakefulness, active wakefulness, movement. The main component of EEG rhythm in all states was confined to the low-frequencies – up to 5 Hz – with the exception of movement functional state when a slight increase of power was observed above 5 Hz (6-8 Hz). The frequency of the main peak was not significantly different across functional states, but active and passive wakefulness revealed considerable interhemispheric differences. Comparison of the power spectra in the lowest frequency range (1-3 Hz), corresponding to the sleep state in adult birds, revealed the significant difference among functional states with the greatest spectral power during the day sleep and the smallest power – during movements. In the range of 3-5 Hz, significant interhemispheric differences were found. Comparison of the power spectra in the high-frequency range corresponding to calm wakefulness (5-12 Hz) and active wakefulness (12-20 Hz) in adult birds, showed the significant differences among functional states with the lowest value of the spectral power during the day sleep and the highest ones – during movements. Paired comparisons revealed only the significant differences between movements and other functional states. The results showed that nestlings’ EEG lacked the clearly marked dominating rhythm characteristic for any certain functional state; this may be due to a very fast (less than 1 sec) change of rhythmic components in EEG. Interhemispheric asymmetry in the main peak frequency during active and passive wakefulness suggests different functional role of two hemispheres in wakefulness states.