Vocal development in nestling kea parrots (<i>Nestor notabilis</i>)

This study investigates vocal development of nestling kea parrots (<i>Nestor notabilis</i>). First, we examine how many structurally distinct call types were present during the nestling period, and the age in which call types occurred. 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. 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. 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. Second, we tested whether nestlings could be discriminated individually based on their calls. All four call types were individually discriminable from hatching until the end of the study, thus providing evidence for vocal signatures. While the function of vocal signatures cannot be ascertained from this study, kea breeding biology rules out explanations based on preventing misdirected parental care. We suggest that vocal signatures may be relevant to the division of parental resources in the nest.本研究聚焦啄羊鹦鹉（kea parrot，学名*Nestor notabilis*）雏鸟的发声发育进程。其一，本研究考察了雏鸟阶段存在的结构差异化鸣叫声型（call types）数量，以及各鸣叫声型的出现日龄。基于其他鸟类的相关研究，我们预设啄羊鹦鹉雏鸟会拥有多种鸣叫声型，其中部分在破壳时即已存在，其余则会在雏鸟期后续阶段出现。研究结果显示，雏鸟共存在4种独立鸣叫声型：2种于破壳时便已存在，另外2种则在雏鸟出生后第二周发生显著体格变化时出现。其中2种鸣叫声型会逐步向成体鸣唱结构演化，剩余2种则无此类发育特征，显然仅用于巢内通讯。其二，本研究测试了能否通过鸣叫声实现雏鸟的个体区分。结果表明，从破壳至本研究结束的全过程中，4种鸣叫声型均具备个体区分能力，由此为个体发声标识（vocal signatures）提供了实证支持。尽管本研究无法明确个体发声标识的功能，但啄羊鹦鹉的繁殖生物学特征排除了“防止亲代抚育误投”这一解释。我们推测，个体发声标识或与巢内亲代资源分配存在关联。