Development of species identification in ducklings: XII. Ineffectiveness of auditory self-stimulation in wood ducklings (Aix sponsa).

A previous study revealed that wood ducklings vocalize copiously when in auditory isolation. However, such self-stimulation appeared to be ineffective in maintaining their preference for the characteristically descending frequency-modulated (FM) notes of the wood duck maternal call. Only isolated birds that had been exposed to a recording of descending sib calls showed the normal preference for descending maternal notes in a choice test with descending and ascending maternal calls. In this study, the actual vocalizations of stimulated and unstimulated wood ducklings were examined in order to explore the possibility that there is a difference in the kind and/or amount of auditory self-stimulation in the two groups (e.g., the stimulated birds might produce more descending calls). Although the stimulated birds produced more ascending notes than the unstimulated birds, no differences were found in the overall vocal behavior, vocal reactivity, or specific kinds of frequency modulation produced by the birds that preferred the descending maternal call and the other birds that responded in the choice test. The absence of a difference in vocal production between the birds that preferred the descending call and the other responding birds supports the previous conclusion that self-stimulation apparently plays no role in the development or maintenance of the species-typical perceptual preference for the descending FM notes of the wood duck maternal call.