Dialects and Duets in Yellow-Naped Amazons
I have been studying yellow-naped amazons, Amazona auropalliata, in the dry forests of Costa Rica for more than a decade. Parrots, like humans, are capable of vocal learning. Research on parrots thus has the potential to offer parallels into learning processes or patterns that occur in humans. Much of my research has focused on yellow-naped amazon duets, in which males and females coordinate their calls. I have been investigating these duets through observation and experimentation in the field, and through acoustic analysis in the laboratory. My research has shown that yellow-naped amazons use their duets to defend their territories from usurpation. I have also identified a series of syntactic rules that the birds use when organizing their duets. Yellow-naped amazons also exhibit patterns of geographic variation known as dialects, in which the structure of calls change. These dialects are currently the focus of an on-going 20+ year study.
YNA photo courtesy of Hugo Cobos
YNA photo courtesy of Hugo Cobos
Long-Term Monitoring of Cultural Evolution in Parrot Vocal DialectsCultural processes, including imitation learning, are a critical means by which behavioral variation is maintained within populations. Vocal dialects represent a useful model with which to study cultural evolution in animals, and are represented in relatively few taxa. Previous surveys conducted over an 11 year span revealed that the geographic boundaries of dialects in yellow-naped amazons are stable, while the stability of call structure varies depending on the dialect. I am collaborating with Dr. Timothy Wright of New Mexico State University to determine whether dialects have remained stable over a more than 20 year span of time, and are also investigating dialects within Nicaragua. This research will broaden our understanding of cultural processes that are transmitted via imitation learning, which offers parallels to learning processes in both primates and humans. Yellow-naped amazons are a threatened species that is declining across their range, and we will also aid ongoing conservation efforts by conducting population surveys during our 2016 survey.
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Spectrograms of duets given by yellow-naped amazons in the Northern and Southern dialects in Costa Rica. The sex of the bird giving the note is indicated. Note how the note types are different between the two dialects, but the overall structure of the duets are very similar. |
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Structure of Ornery Duets in the Yellow-Naped Amazon
Yellow-naped amazons give two types of duets; standard and warble forms. The standard duets have relatively few note types and we have identified their role in territory defense. My students are now studying warble duets, which are much more variable in form and appear to be used in more aggressive contexts. We have identified 39 visually distinct types of notes in warble duets, in contrast to the four types found within standard duets. Questions we are currently pursuing include:
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