@article {53364,
	title = {Quiet violence: Savannah Sparrows respond to playback-simulated rivals using low-amplitude songs as aggressive signals},
	journal = {Ethology},
	volume = {124},
	year = {2018},
	month = {Jan-10-2018},
	pages = {724 - 732},
	abstract = {<p>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 \&ldquo;soft songs,\&rdquo; 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 \&ldquo;chip\&rdquo; 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.</p>
},
	keywords = {aggressive signalling, animal communication, low-amplitude vocalizations, Savannah Sparrows, soft songs},
	doi = {10.1111/eth.2018.124.issue-1010.1111/eth.12805},
	url = {http://doi.wiley.com/10.1111/eth.2018.124.issue-10},
	author = {Moran, Ines G. and Doucet, St{\'e}phanie M. and Newman, Amy E. M. and Ryan Norris, D. and Mennill, Daniel J.},
	editor = {Koenig, W.}
}
@article {50491,
	title = {Sexual differentiation and seasonal variation in response to conspecific and heterospecific acoustic signals},
	journal = {Ethology},
	volume = {123},
	year = {2017},
	month = {Jan-06-2017},
	pages = {460 - 466},
	abstract = {<p>Interspecific territoriality is frequently reported between closely related species; however, few studies have demonstrated interspecific territoriality between distantly related species living in sympatry. We conducted playback experiments to investigate territorial behaviour in male and female White-bellied Wrens (Uropsila leucogastra) in response to simulated conspecific and heterospecific intruders during the breeding and non-breeding seasons. We explored whether heterospecific songs of the Happy Wren (Pheugopedius felix), a distantly related species and ecological competitor, elicited antagonistic responses from focal White-bellied Wrens, and whether such responses differed between the sexes. We also examined whether male and female responses to conspecific and heterospecific rivals varied with season. We found that male White-bellied Wrens always responded to conspecific song, and responded significantly more to heterospecific song compared to a control stimulus (Tropical Parula, Setophaga pitiayumi). In contrast, although female White-bellied Wrens responded strongly to conspecific song, their response to heterospecific song did not differ significantly from the control stimulus. The proportion of males that responded to heterospecific songs and the proportion of females that responded to conspecific songs varied seasonally, showing significantly lower responses during the breeding season. The intense responses of male White-bellied Wrens to playback of heterospecific songs suggest that they recognise ecological competitors based on their vocal signals. Furthermore, the decrease in agonistic interactions during the breeding season is in line with the hypothesis that aggressive behaviour may be detrimental to reproductive and parental activity, and the hypothesis that heterospecific animals pose less of a threat during the breeding season.</p>
},
	doi = {10.1111/eth.12616},
	url = {http://doi.wiley.com/10.1111/eth.12616},
	author = {Sosa-L{\'o}pez, J. Roberto and Mennill, Daniel J. and Renton, Katherine},
	editor = {Koenig, W.}
}
