Selective resistance to approach: a precursor to fear responses to an alarm call in great tit nestlings Parus major.

The reactions of 10-day-old great tit nestlings to 3 auditory stimuli were studied. The stimuli, presented on a series of feeding occasions, were (1) the species' "sweet" alarm call, (2) a song strophe of the great tit, and (3) a song strophe of the tree-creeper (Certhia familiaris). In contrast to earlier findings in studies of older nestlings, these younger nestlings did not respond to the alarm call with cessation of begging. However, a significant differential effect of the alarm call was demonstrated when the conditioning rates for the nestling' begging response to each of the 3 stimuli were determined. Thus, conditioning was significant slower to the alarm call than to the other stimuli. The results agree with the general conception that responses to species-specific calls develop gradually during early ontogenesis. Thus fear responses to the alarm call, such as cessation of begging and "freezing," which are elicited in newly fledged young, are preceded by weaker aversive tendencies that are not obvious from observations of the nestlings' behavior in nature. It is suggested that the nestlings' exposure to contrasting auditory stimulation-their own begging call and the parental feeding call-constitutes the experiential base for withdrawal responses to the "sweet" call.