Behaviour 2019
Song amplitude mediates social interactions in Long-billed hermit hummingbirds (Phaethornis longirostris)
Melanie L. Talavera-Arboniés1, Paulina L. González-Gómez2, Marcelo Araya-Salas3. 1Department of Biology, University of Puerto Rico, Mayagüez , , Puerto Rico; 2Department of Wildlife, Fish, and Conservation. University of California, Davis, CA, United States; 3Neuroscience Investigation Center, University of Costa Rica, San Pedro, San José, Costa Rica

Understanding the role of song amplitude (i.e. loudness) in animal communication has been challenging because measurements can be affected by environmental noise, recording settings, distance, and orientation. We developed a standardized method to measure amplitude consisting of placing recorders below singing perches of Long-billed hermits to control recording distance and orientation. Variation in song amplitude (measured as sound pressure level, SPL) was evaluated for different social contexts and related to proxies of condition. We found that individuals sing at higher SPL in the morning (when feeding resources peak) and that variation in SPL among individuals is poorly correlated with proxies of condition. However, SPL increased in ~2dB after male-male aggressive encounters. Coordinated singing and playback experiments induced change in SPL, but the direction of the response (higher or lower) vary across individuals. Lastly, we found that singing at higher SPL did not affect song consistency. Our findings posits song amplitude as a flexible acoustic feature used in different social conexts and suggests that it could be an important parameter for evaluating vocal responses.