Like many other naive young birds, great tit nestlings, Parus major, respond by a persistent cessation-of-begging and immobility response to the ‘seeet’ alarm-call of the species (Rydén 1978). The experimental antecedents of this reaction were investigated through a systematic manipulation of the auditory environment preceding it. Limiting nestlings' experience with the ‘seeet’-call to either a “positive”, a “neutral” or a “negative” setting led to their normal aversive response to the call being weakened, unaltered and strengthened, respectively. Nestlings brought up in a “reversed”, artificial environment showed a radical decrease in their aversive response. The results lend support to the hypotheses that a) the ‘seeet’-call owes its aversive effect to the fact that its acoustic character contrasts sharply with the main features of the nestlings' normal auditory environment; b) context-specific experiences may either increase or decrease this basic response tendency. Some functional implications of the results as related to the behavior of the species in nature are discussed.