02184nas a2200181 4500008004100000245009100041210006900132520157400201653002501775653002501800653001301825653002201838653001401860653002401874100002501898700002401923856005501947 2020 eng d00aSong-type switching rate in the chaffinch carries a message during simulated intrusion0 aSongtype switching rate in the chaffinch carries a message durin3 a

Birds communicate their motivation and willingness to escalate a territorial conflict with a variety of agonistic signals. One of these, song-type switching, has been suggested to be a conventional signal in male–male interactions. However, this behavior does not show a consistent pattern across species. In this study, we asked whether variation in song-switching rate carries a message for song receivers among territorial chaffinches, Fringilla coelebs. Chaffinch song is well described, but only a few studies have focused on the communicative function of song-type switching or bout duration. Using data from playback experiments, we show here that variation in song-type switching rate affects the response of chaffinches. In response to the low switching rate treatment, territorial males began to sing later, produced fewer songs and more rain calls, decreased flight intensity, and spent more time close to the speaker than during playback of songs with a high switching rate. Our results provide strong evidence that the song-type switching rate is an agonistic signal in the chaffinch and that territorial males exhibit a stronger response toward rivals that sing with a lower song-type switching rate. A secondary purpose of our study was to determine the receivers’ response with respect to their own song rate and song repertoire. We found that the reaction of tested males was correlated with their own spontaneous song rate. This implies that a male’s response to stimuli may be predicted on the basis of his own song output.

10aAggressive signaling10aanimal communication10abirdsong10aFringilla coelebs10asong rate10aSong-type switching1 aDeoniziak, Krzysztof1 aOsiejuk, Tomasz, S. uhttp://link.springer.com/10.1007/s00265-020-2825-202516nas a2200217 4500008004100000245010300041210006900144260001600213490000700229520180700236653002502043653002402068653001302092653001402105653002202119653001802141653001702159100002502176700002402201856007302225 2019 eng d00aHabitat-related differences in song structure and complexity in a songbird with a large repertoire0 aHabitatrelated differences in song structure and complexity in a cJan-12-20190 v193 a

Background

Urbanisation has been shown to influence many aspects of animal vocal communication. Much attention has been paid to anthropogenic noise, which is often described as one of the most challenging disturbances for urban dwellers. While a large body of literature describes associations between vocal behavior of avian populations and background noise level, most of these studies were conducted on species with relatively simple songs and small repertoire sizes. This study focuses on the song thrush, Turdus philomelos, a common Eurasian songbird with a complex singing style and large syllable repertoire. Our objective was to determine whether frequency, repertoire and temporal organisation of song parameters vary between birds inhabiting urban and adjacent forest habitats in which ambient noise levels differ.

Results

Songs of urban males were found to be more complex than in conspecifics from natural forest populations. Urban dwellers possessed greater syllable repertoires and repeated syllable sequences more often. In addition, they used a smaller proportion of whistles and a higher proportion of twitter syllables when singing compared to the nonurban males. Moreover, we found significant differences in the minimum and peak frequency of the whistle syllable between studied populations.

Conclusions

These findings may be an example of adaptation of acoustic communication in noisy urban environments, but we also discuss other possible explanations. We emphasize the need for further investigation into the relationships between birdsong and habitat characteristics, male quality, population density and ambient noise level in populations occupying urban and nonurban habitats.

10aanimal communication10aanthropogenic noise10abirdsong10asongbirds10aTurdus philomelos10aUrban ecology10aurbanisation1 aDeoniziak, Krzysztof1 aOsiejuk, Tomasz, S. uhttps://bmcecol.biomedcentral.com/articles/10.1186/s12898-019-0255-702360nas a2200205 4500008004100000245010700041210006900148260001600217300001400233490000800247520169800255653002301953653002001976653001401996653002402010100002702034700002402061700001502085856005402100 2018 eng d00aSoft songs in male ortolan buntings are used in an aggressive context but are not an aggressive signal0 aSoft songs in male ortolan buntings are used in an aggressive co cJan-08-2018 a549 - 5580 v1243 a

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.

10aAggressive signals10aortolan bunting10asoft song10aterritorial defence1 aJakubowska, Aleksandra1 aOsiejuk, Tomasz, S.1 aFusani, L. uhttp://doi.wiley.com/10.1111/eth.2018.124.issue-802625nas a2200205 4500008004100000022001300041245006400054210006400118260001600182300001400198490000800212520182300220653002302043653002302066653002402089653002202113100002702135700002402162856023302186 2018 eng d a0376635700aSing softly to evoke a response only from a recent intruder0 aSing softly to evoke a response only from a recent intruder cJan-12-2018 a244 - 2490 v1573 a

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.

10aAggressive signals10aEmberiza hortulana10aplayback experiment10aTerritory defence1 aJakubowska, Aleksandra1 aOsiejuk, Tomasz, S. uhttps://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