@article {53369,
	title = {Soft songs in male ortolan buntings are used in an aggressive context but are not an aggressive signal},
	journal = {Ethology},
	volume = {124},
	year = {2018},
	month = {Jan-08-2018},
	pages = {549 - 558},
	abstract = {<p>Many bird species produce low-amplitude acoustic signals that have been poorly studied in comparison with loud, broadcast songs used for mate attraction and repelling rivals. In some birds, these soft signals were found to be emitted in an antagonistic context and were the most reliable predictor of a subsequent physical attack. The function of this signal is poorly understood, and several hypotheses have been proposed to explain the mechanisms and possible functions of such low-amplitude signals. The subject of this study is the ortolan bunting, a small passerine species that produces soft songs during territorial defence. In this study, we aim to study whether the soft songs of the ortolan bunting are a signal of increased aggressiveness by testing if they meet the context, prediction and response criteria of aggressive signals. We simulated stranger male intrusion into a focal male territory with three different playback experiments. We found no significant differences in the male responses to the taxidermic model regardless of whether they were or were not producing soft songs in response. The males responded more strongly to loud songs than to soft songs during the simulated intrusions, and the males did not treat soft songs as a predictor of conflict escalation. Although soft songs clearly appeared during territorial encounters and were not present during spontaneous singing before the intrusions, our results did not support the hypothesis that soft songs indicate aggressive character. We suggest that soft songs in the ortolan bunting are intentionally used by birds to modify their intentions or target-specific individuals within a close range.</p>
},
	keywords = {Aggressive signals, ortolan bunting, soft song, territorial defence},
	doi = {10.1111/eth.2018.124.issue-810.1111/eth.12758},
	url = {http://doi.wiley.com/10.1111/eth.2018.124.issue-8},
	author = {Jakubowska, Aleksandra and Osiejuk, Tomasz S.},
	editor = {Fusani, L.}
}
@article {53261,
	title = {Sing softly to evoke a response only from a recent intruder},
	journal = {Behavioural Processes},
	volume = {157},
	year = {2018},
	month = {Jan-12-2018},
	pages = {244 - 249},
	abstract = {<p>Low-amplitude soft songs have been described in many birds, but in most species, research has addressed only broadcast songs. Soft songs may have a similar or distinctive structure in comparison to broadcast songs produced in order to defend a territory and attract females. In some species, such soft songs were found to be produced in an aggressive context and were the best predictors of conflict escalation and later physical attack. However, such observations are not consistent across all species studied. Several hypotheses have been put forward to explain the function(s) of soft songs and why they are so quiet. Studies on the ortolan bunting (Emberiza hortulana) show that males produce soft songs similar in structure to broadcast songs during close interactions with conspecific intruders. However, experiments with the playback of loud and soft songs as well as taxidermic mount presentation revealed that soft song in this species does not fulfil aggressive signal criteria. Here we performed an experiment with two loudspeakers simulating movements of the intruder in order to test whether the soft songs are used to evoking a response from a nearby but not localised rival. We found that males responded with similar strength to songs played back from single and double speaker systems. Simultaneously, males produced more soft songs during and just after the phase of the experiment in which we simulated short flights of the intruder. Our results indicate that soft songs might be used during close interactions with rivals without being an aggressive signal and are used as short-range signals to check if the rival is still around. Our results also provide an alternative explanation of soft song behaviour in comparison to the hypotheses of eavesdropping avoidance and readiness to fight.</p>
},
	keywords = {Aggressive signals, Emberiza hortulana, playback experiment, Territory defence},
	issn = {03766357},
	doi = {10.1016/j.beproc.2018.10.012},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0376635718301335https://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/plain},
	author = {Jakubowska, Aleksandra and Osiejuk, Tomasz S.}
}
