ИСТИНА

Endothermy, a high level of organization, the development in the egg make birds a convenient model for studying behavior in early ontogenesis. A variety of ontogeny types in birds form a series that allows for a comparative study of the development of sensory systems, in particular, hearing, and acoustically guided behavior. Hearing sensitivity develops early than vision in endothermic animals. Feeding behavior forms first in the ontogeny of birds and mammals, then defensive behavior formed as freezing reaction, which followed by escape reaction.The nature of changes and fluctuations in RR intervals of ECG (HVR variability) adequately reflects the general functional state of the pied flycatcher (Ficedula hypoleuca) nestlings and the main pattern of behavior, feeding and defense reactions.