Evidence for maintenance of key components of vocal learning in aging budgerigars despite diminished affiliative social interaction

In some species, the ability to acquire new vocalizations persists into adulthood and may be an important mediator of social interactions. While it is generally assumed that vocal learning persists undiminished throughout the lifespan of these open-ended learners, the stability of this trait remains largely unexplored. We hypothesize that vocal learning exhibits senescence, as is typical of complex cognitive traits, and that this decline may relate to age-dependent changes in sociality. The budgerigar (Melopsittacus undulatus), an open-ended learner which develops new contact call types that are shared with social associates upon joining new flocks, provides a robust assay for measuring the effects of aging on vocal learning ability. We formed captive flocks of 4 previously unfamiliar adult males of the same age class, either "young adults" (6 mo.-1 yr.) or "older adults" (≥ 3 yr.), and concurrently tracked changes in contact call structure and social interactions over time. Older adults exhibited decreased vocal diversity, which may be related to the sparser and weaker affiliative bonds observed in older adults. Older adults, however, displayed equivalent levels of vocal plasticity and vocal convergence compared to young adults, suggesting vocal learning ability is largely maintained into later adulthood in an open-ended learner.