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Vocal development and patterns of vocal variation inform conservation of a critically endangered macaw

Allison, Alexander1; Jimenez, Mario2; Wright, Timothy1

Published Apr 23, 2026 on Dryad. https://doi.org/10.5061/dryad.z8w9ghxrb

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Abstract

Reintroductions are increasingly used as a tool to bolster declining populations of birds, but the potential for communication barriers arising from learned vocal variation between introduced and wild populations has rarely been considered. The critically endangered great green macaw, Ara ambiguus, is one such declining species, but it is currently unknown whether there is vocal variation in adult contact calls among geographically isolated populations. Furthermore, variation in nestling calls among populations has never been investigated and could offer insight into how the nestling social environment shapes the formation of dialects. We investigated whether adult and nestling great green macaws show among-population variation in the acoustic structure of their calls by recording vocalizations in one wild, one captive, and one reintroduced population in Costa Rica. We assessed acoustic similarity among the three populations by measuring 26 parameters from the spectrogram of each call and performing spectrographic cross-correlation. We tested for population differences in the acoustic structure of adult and nestling calls using linear mixed models and Mantel tests. Only minimal variation was detected among adult contact calls from the three populations. During mid-development, nestling calls showed variation among populations that may be explained by individual morphological differences and overproduction of call types. Minimal variation later in development may be explained by selective attrition of the vocal repertoire as well as vocal convergence driven by the pressure to form and maintain flocks during adulthood. Investigating adult and nestling calls across isolated populations of threatened parrot species can give insight into how vocal variation develops among populations and when conservation managers should consider vocal differences between released and wild birds during the reintroduction process.