02429nas a2200253 4500008004100000245012300041210006900164260001600233300001400249490000800263520160100271653002601872653002501898653003401923653002201957653001501979100002001994700002702014700002302041700001702064700002402081700001502105856005502120 2018 eng d00aQuiet violence: Savannah Sparrows respond to playback-simulated rivals using low-amplitude songs as aggressive signals0 aQuiet violence Savannah Sparrows respond to playbacksimulated ri cJan-10-2018 a724 - 7320 v1243 a
When animals compete over resources such as breeding territories, they often use signals to communicate their aggressive intentions. By studying which signals are associated with aggressive interactions, we gain a deeper appreciation of animal behaviour. We studied aggressive signalling in male Savannah Sparrows, Passerculus sandwichensis, focusing on signals that precede physical attack against territorial intruders. We simulated intruders using song playback and taxidermic models, and we determined which behaviours were associated with physical attack. Previous studies that have used this approach suggest that many species produce songs of dramatically lower amplitude, or “soft songs,” as signals of aggressive intention. Savannah Sparrows, however, are not known to produce soft songs, and therefore, they provided an interesting system for testing signals that predict attack. Of 93 playback subjects, 23 males attacked the simulated intruder and 70 did not. To our surprise, Savannah Sparrows produced soft songs, and the number of soft songs was a significant predictor of attack on the simulated intruder. Birds also showed a nonsignificant tendency to produce more “chip” calls prior to attack on the simulated intruder, whereas three other measured behaviours (aggressive calls, wing waving and passes over the model) did not predict attack. Our study contributes to the growing body of research on aggressive territorial signals and reveals that soft song is an even more widespread signal of aggression in songbirds than previously recognized.
10aaggressive signalling10aanimal communication10alow‐amplitude vocalizations10aSavannah Sparrows10asoft songs1 aMoran, Ines, G.1 aDoucet, Stéphanie, M.1 aNewman, Amy, E. M.1 aNorris, Ryan1 aMennill, Daniel, J.1 aKoenig, W. uhttp://doi.wiley.com/10.1111/eth.2018.124.issue-10