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Brown-throated parakeet vocalization data

Citation

Eberhard, Jessica; Zager, Irene; Ferrer-Paris, Jose; Rodriguez-Clark, Kathryn (2021), Brown-throated parakeet vocalization data, Dryad, Dataset, https://doi.org/10.5061/dryad.k3j9kd58b

Abstract

Learned vocalizations play a key role in parrot social dynamics and vocal dialects have been documented for several mainland species, but to date no studies of geographically structured call variation in parrot species have examined the role of isolation on islands. In a study of the Brown-throated Parakeet (Eupsittula pertinax), which inhabits five small Caribbean islands as well as the adjacent mainland, we found that the contact calls of island and mainland parakeets show divergence in vocal characters as well as in call variability. We assessed call variation using three approaches: frequency measurements, spectrogram cross-correlation (SPCC) analyses, and call duration measurements. Island parakeets’ calls were longer and had lower mean frequencies, and calls from different islands were distinguishable from each other as well as from mainland calls using measures derived from the SPCCs. In addition we measured call variability at two different levels—within-location and within-individual. We found calls to be more variable for island parakeets for SPCC and duration measures, but less variable for frequency measures. The observed call differentiation among locations may be due to drift, while the lower frequency of island calls could either be a response to the very windy environment on the islands or a consequence of the island subspecies’ larger body sizes. We also hypothesize that the isolation of parakeet populations on very small islands may have resulted in reduced selection for local call convergence, allowing island parakeets to produce more variable calls. We suggest that due to poor signal transmission in the windy island environment, selective pressures may favor variability in more easily perceived call features (like call duration) rather than more subtle features, like frequency shifts. Experimental tests are required to determine whether observed call patterns translate into similarly structured patterns in the responses to vocal variants.

Usage Notes

For information/notes on the archived files, see: Eberhard_etal_data_README.txt

Funding

National Geographic Society, Award: 7096-01

Fondo Nacional de Ciencia Tecnología e Innovación, Award: 2001000902