Cultural atlas of vocal variation in the yellow-naped amazon parrot

Vocal dialects are a taxonomically widespread phenomenon, which are
usually studied in a restricted portion of a species’ range. It is unclear
whether geographic patterns observed in one part of a species’ range can
be inferred as typical across the range or whether local conditions
influence the presence or absence of dialects. We examined the
yellow-naped amazon, Amazona auropalliata, a parrot species with
remarkable vocal learning capabilities. Although this species is native to
Mesoamerica, only Costa Rican populations have been evaluated long-term.
Previous studies have shown that these populations exhibit geographically
and temporally stable vocal dialect patterns. Without data on populations
outside of Costa Rica, it is impossible to know if vocal dialects are
present in northern range populations, and whether or not they exhibit
similar geographic structure to southern range populations. We recorded
yellow-naped amazon contact calls at 47 different sites across the range
between 2016 and 2019 and evaluated them for the presence of dialects. We
visually classified 14 contact call types based on spectrographic
similarity and used spectrographic cross-correlation, principal component
analysis, and Mantel-based spatial autocorrelations to assess acoustic
similarity. The results from our study show that the vocal patterns
previously seen in Costa Rica are also present in northern range
populations, supporting our hypothesis. Call types were regionally
specific (e.g., vocal dialects) across the range, and no call types were
repeated across multiple regions. We did, however, observe distinctive
structural characteristics that are found in multiple call types,
suggesting that different call types stem from a common origin. Vocal
dialect in this species is likely maintained through a tendency toward
philopatry and matching call types to enhance social identification.