Responses of young zebra finches towards different stimuli were tested between hatching and 20 days of age. The stimuli applied were: tactile stimulation with a stick, acoustic stimulation from a loudspeaker playing begging calls of other nestlings, and stuffed dummies of zebra finches and Bengalese finches as visual stimuli. Tactile and acoustic stimuli resulted in gaping responses from the first day of life. Visual stimuli elicited gaping from about day 10 or 11, 4 days after the opening of the eyes. At day 13, gaping responses towards stimuli decreased and were replaced by fear responses from day 16. The implications of the results for sensory development and imprinting are discussed. The development of fear in the young zebra finches is compared with results from filial imprinting.