Is the Periodic “Spontaneous” Activity of Animals Determined by a Quasi-Rhythmic Factor of the External Environment?

We have studied the dynamics of the singing of garden bunting ( Emberiza hortulana ) and the dispersal of a flock of starlings ( Sturnus vulgaris ) for the night rest. The results were compared with the body temperature fluctuations measured in parallel in a group of laboratory mice. The validity of such comparisons was determined by the presence of a stable correlation between the indicators of minutely changes in body temperature in mice and greenfinches ( Chloris chloris ). The increase in the frequency of chanting of garden buntings was observed simultaneously with the increase in body temperature in mice. Moreover, the exact moments of the flights into the birdhouse for the night in starlings coincided with the maximums in the dynamics of minutely changes in body temperature of mice. These facts suggest an external synchronizer of “spontaneous” fluctuations of the activity and associated changes in body temperature, which are probably determined by the tone of the sympathetic nervous system.