Both nestlings and parents may reduce the risk of predator detection by producing calls of low amplitude and high entropy which are acoustically difficult to locate. Research on passerines has shown that parents may reduce the risk of nest predation by alarm calling to warn nestlings to be quiet, and by producing food calls which solicit begging when parents are present to defend the nestlings. Offspring beg to attract parents’ attention, thus increasing the chances of being fed, but also increasing the chances of being detected by predators. Vocal behaviour of nesting altricial birds is subject to selection pressure from several sources. We suggest that vocal signatures may be relevant to the division of parental resources in the nest. While the function of vocal signatures cannot be ascertained from this study, kea breeding biology rules out explanations based on preventing misdirected parental care. All four call types were individually discriminable from hatching until the end of the study, thus providing evidence for vocal signatures. Second, we tested whether nestlings could be discriminated individually based on their calls. While two of the call types developed gradually towards more adult-like structures, the other two did not and were apparently only used for communication in the nest. Results showed that nestlings have four distinct call types, two present at hatching, and two emerging when the nestlings undergo large physical changes in the second week of life. Based on studies with other avian species, we predicted that kea nestlings would have multiple call types, with some present at hatching and others emerging later in the nestling period. ![]() ![]() First, we examine how many structurally distinct call types were present during the nestling period, and the age in which call types occurred. This study investigates vocal development of nestling kea parrots (Nestor notabilis).
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