Abstract
AbstractLike most corvids, adult magpies (Pica pica) have harsh vocal repertoires characterized by a wide distribution of energy over the frequency scale. Shortly after hatching, begging calls of magpie nestlings have a tonal quality but become increasingly noisier as they develop. The appearance of harsh structures in the calls is closely related to a process of frequency modulation which ends at about 16–18 days. At this age, nestlings suddenly develop genuine harsh calls, typical of fledglings and adult birds. During development, similarities can be observed between frequency modulation and noise production, suggesting that nestlings acquire the ability to produce adult harsh vocalizations by modulating their begging calls. This hypothesis does not explain, however, why genuine harsh calls develop without transitional forms being evident in the preceding begging calls. Also, intra‐ and interspecific differences in modulation rates do not cause differences in noise production in the way that this hypothesis would at first suggest. Frequency modulation and noise production do not seem to be involved in the ontogeny of the adult voice. It is suggested that both features contribute to call degradation in the environment, in order to compensate for the increasing risks of nests being detected by predators due to the more detectable calls of older nestlings.
Published Version
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