Development of species identification in ducklings: X. Perceptual specificity in the wood duck embryo requires sib stimulation for maintenance

Abstract

A critical acoustic feature of the wood duck maternal assembly call is the descending frequency modulation (FM) of its notes. To determine the role of exposure of wood ducklings to conspecific vocalizations in the development of selective responsiveness to the descending FM of the species maternal call, the behavioral response of embryos to synthetic descending and ascending maternal calls was examined. Previous work indicated that selective responsiveness of newly hatched wood ducklings to the descending FM of the maternal call is dependent upon prior exposure to descending FM calls of siblings. In advance of auditory experience the youngest embryos were responsive to both ascending and descending call notes, but older aurally isolated embryos became selectively responsive to the descending FM. However, even though the wood duck hatching vocalizes considerably in aural isolation, self-stimulation is ineffective in maintaining the perceptual selectivity in the neonate. Unlike the mallard, in which self-stimulation is adequate, the wood duckling must be exposed to sib vocalizations in order to remain selectively responsive to the critical acoustic feature of the maternal call of its species.