Broadcast Song Research Articles

Vocal functional flexibility in a nonprimate vocal learning species

Abstract Can nonhuman animals use the same acoustic signal to transmit different illocutions on different occasions? This communicative capacity is known as vocal functional flexibility and occurs, for example, in speech, when a sentence serves different illocutionary forces or functions on different occasions based on changes to visual and intonational cues. Although common in human speech, there is a lack of clear evidence for this ability in other species. Here, we examined a likely candidate, the Brown-headed Cowbird (Molothrus ater), which is a vocal-learning songbird species that develops a repertoire of structurally distinct song types. Most of this species’ songs are directed towards conspecific males and females less than a meter away, making it unusually easy to determine the apparent target of songs, unlike the broadcast songs done by most songbirds. Songs directed to other males have clear aggressive/threatening intent, while those to females involve courtship/sexual intent. Extensive prior work shows that male cowbirds perform the visual display that accompanies singing differently in these two social settings and also modulate the intonation of song types differently. Because of these display and tonal modulations, constancy of song type usage across male- vs female-directed singing would provide evidence of vocal functional flexibility. Herein, we examined 4,828 songs in three captive flocks containing twenty-four males and thirty females during the breeding season. Males did not use their song types randomly and had strongly favored songs and less commonly used ones. Importantly, favored song types and less commonly used ones were the same whether directing courtship song to a female, aggressive song to another male or singing nonsocially with no receiver nearby. Results were consistent within and across the three flocks, providing strong evidence of vocal functional flexibility. These findings indicate that some species may evolve the ability to modulate and exaggerate visual display components and prosody more than vocal presentation per se because a learned phonological system in this and possibly other species is constrained by its vital role as an indicator trait.

Copyright Protection Against the Act of Covering Songs on Youtube Channels in the Regulation of Intellectual Property Rights in Indonesia

This study aims to determine and describe the form of copyright protection against the act of covering songs on YouTube channels in the regulation of intellectual property rights in Indonesia. The research method used is normative juridical by examining through literature studies. The results of the research based on Article 5 and Article 9 of Law Number 28 of 2014 concerning Copyright, the creator gets legal protection related to songs uploaded by other parties through Youtube which applies anywhere regardless of the media used to announce a song. In addition, songwriters get legal protection from Youtube, namely Youtube will delete videos that violate copyright, but this is only implemented by Youtube if it has received notification of copyright infringement. The legal consequences for Youtube that continues to broadcast songs uploaded without the creator's permission is the closure of the Youtube site as a whole.

Soft song provokes stronger aggressive responses than broadcast song in the Plain Laughingthrush (Pterorhinus davidi)

Many bird species produce low‐amplitude acoustic signals, known as soft songs, which are widely believed to function primarily in aggressive interactions. However, there are surprisingly few experimental studies that have examined whether soft songs are reliable signalling strategies for escalating aggressive interactions. Here, we investigate the functions of soft song in a colour‐marked population of the Plain Laughingthrush Pterorhinus davidi, using playback experiments combined with specimen‐based simulated territory intrusions. We found that playback of male soft song provoked quicker response and stronger aggressive intent by territorial pairs compared with playback of male broadcast song. Responses by territorial pairs to male soft song playback were significantly stronger compared with responses to broadcast song playback, with a greater number of flights over the speaker, more time spent within 1 m of the speaker and closer approaches to the speaker. Furthermore, closer approach with the production of soft song by focal males was the best predictor of aggressive intent in combined playback and specimen intrusion experiments. Our results suggest that male soft song is used as an aggressive signal in the Plain Laughingthrush, and represents the first evidence of such for a monogamous temperate duetting species.

A method for estimating songbird abundance with drones

Using drones to conduct airborne bioacoustics surveys is a potentially useful new way to estimate the abundance of vocal bird species. Here we show that by using two audio recorders suspended from a quadcopter drone it is possible to estimate distances to birds with precision. In an experimental test, the mean error of our estimated distances to a broadcast song across 11 points between 0 and 100 m away was just 3.47 m. In field tests, we compared 1 min airborne counts with 5 min terrestrial counts at 34 count locations. We found that the airborne counts yielded similar data to the terrestrial point counts for most of the 10 songbird species included in our analysis, and that the effective detection radii were also similar. However, airborne counts significantly under-detected the Northern Cardinal (χ29 = 22.8, post-hoc test P = 0.007), which we attribute to a behavioral response to the drone. Airborne counts work best for species that vocalize close to the ground and have high-frequency-range songs. Under those circumstances, airborne bioacoustics could have several advantages over ground-based surveys, including increased precision, increased repeatability, and easier access to difficult terrain. Further, we show that it is possible to do rapid surveys using airborne techniques, which could lead to the development of much more efficient survey protocols than are possible using traditional survey techniques.

Legal Protection On Song Creators Royalties That Doesn't Paid By Karaoke Business Actor That Violence The Law Of Number 28 Of 2014

The development of the karaoke business has a very broad prospect in the business world as evidenced by the large profits that have triggered many karaoke businesses to play and broadcast songs for commercial purposes. Karaoke business actor who have used commercial copyright are obliged to pay a fee or royalty to the song creators. The collection of royalties is carried out by the Collective Management Institute (LMK) to karaoke entrepreneurs with the aim that song creators obtain their rights, namely economic rights. A karaoke business actor that carries out business activities for commercial purposes, namely broadcasting songs without paying royalties to the song creators, the impact will be detrimental to the song creators. The method used in this study is the normative juridical approach, this research is in accordance with the laws and regulations relating to copyright, namely Law Number 28 of 2014. The purpose of this study is to reduce the actions of karaoke business actors who do not pay royalties to the creator song, then Law Number 28 Year 2014 provides legal protection to song creators from the rise of commercialization actions done by karaoke business actors without paying royalties to song creators by providing legal protection to song creators through repressive efforts, legal remedies that can be done song creators based on Law Number 28 of 2014 can be reached through litigation and non-litigation. By optimizing Law Number 28 of 2014, the protection of song creators can be carried out perfectly. Sanctions imposed on karaoke business actors who do not pay royalties can be carried out in a civil and criminal manner, to guarantee legal protection for songwriters or copyright holders there must be cooperation not only from the Directorate General of Intellectual Property and LMK, but from business actors , community and law enforcement.

Hey mister Tambourine Dove, sing a song for me: simple but individually specific songs of Turtur tympanistria from Cameroon

BackgroundThe broadcast song of the Tambourine Dove (Turtur tympanistria) is a repetitive coo series produced in a very stereotyped way. The song is similar to those of the other species within the Turtur genus and likely reflects the adaptation to long distance signalling in tropical habitats. There is no study assessing individual variation of the Tambourine Dove song or for the possibility of identity coding through song features.MethodsWe obtained recordings of 578 songs from 41 males within a population inhabiting montane forest in Cameroon between 2008 and 2018. Additionally, we analysed also recordings from automatic recorders working for a longer time during the year. Songs were analysed to get basic information about within- and between-individual spectro-temporal variation. Potential of identity coding and discriminant analyses were used to investigate if and how these songs may convey information about male identity.ResultsThe song of the Tambourine Dove is a very simple series of short, unmodulated whistles with low frequency and a narrow bandwidth. Measurements of single song features indicated either none or a weak potential for identity coding. The overall variation in song frequency characteristics was very low. However, the number of notes forming a song (and consequently the duration) had a similar variability both within- and between individuals. When using multiple song measurements discrimination analysis revealed a high potential for identity coding although it seems that the temporal pattern of the beginning of a song carries the most information about sender identity. The production of initial notes within a song has very precise, individually specific timing allowing for up to 96.7% correct recognitions of songs. Comparison of recordings from the same points but separated in time by over a month indicates that song parameters are individually stable over longer period.ConclusionsDespite having highly stereotyped and simple songs, Tambourine Dove males produce individually specific signals which have a great potential for recognition by rivals or mates. All Turtur doves have similar yet unique songs that are different to the songs of other pigeon species. This genus seems to be a perfect model for studying the trade-off between coding for species identity and individual identity in a non-learning bird species. The described method of individual recognition allows for nonintrusive population monitoring.

Dangerous love? Predation risk does not affect female mate choice in blue‐black grassquits

AbstractPredation risk may be an important factor affecting female mate choice. Hypothetically, females could choose extravagantly ornamented males that survive in high predation risk environments. However, this decision could be different if choosing a conspicuous male under high predation risk is costly for females or results in reduced offspring survival. In such contexts, females could become indifferent to male quality or prefer inconspicuous males. We tested this idea using captive blue‐black grassquits (Volatinia jacarina, Linnaeus, 1766), a species in which males perform conspicuous leap displays coupled with songs during the breeding season, which presumably subjects females and offspring to higher predation risk. Females were placed in an arena with speakers on opposite sides emitting male courtship songs. One speaker emitted songs at a high rate (proxy for a conspicuous male) while the other speaker broadcast songs at a low rate (proxy for a less conspicuous male). While the female evaluated the two male songs, a third speaker emitted vocalizations characterizing three levels of risk: adult predator, nest predator, and no‐risk control. Females showed no preference for either male stimuli across the predation risk treatments. This lack of preference relative to frequency of male vocal displays suggests that leap‐song frequency is not used by females during mate choice. We suggest that in addition to its role in courtship, male grassquit displays also signal status to other males when competing for territories. Thus, we propose that predation risk does not directly influence blue‐black grassquit intersexual selection and that females in this species may exercise indirect mate choice, choosing social mates based on male ability to establish and defend a territory, and relying secondarily upon other aspects of male display attributes, such as its visual components.

Sing softly to evoke a response only from a recent intruder

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.

Soft songs in male ortolan buntings are used in an aggressive context but are not an aggressive signal

AbstractMany 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.

A test of the eavesdropping avoidance hypothesis as an explanation for the structure of low-amplitude aggressive signals in the song sparrow

Low-amplitude signals function in private exchanges of information between signalers and nearby receivers. The eavesdropping avoidance hypothesis proposes that selection favors quiet threat signals in order to avoid the costs of eavesdroppers. If true, then selection should favor other acoustic traits in addition to low amplitude that lead to quiet signals transmitting less effectively through the environment compared to broadcast signals. The “warbled” soft songs of male song sparrows differ from “crystallized” soft songs and from broadcast songs in a number of acoustic traits, suggesting that these songs may transmit less effectively. We tested this prediction in a field experiment by playing broadcast songs, crystallized soft songs, and warbled soft songs through a loudspeaker at the same amplitude and recording the propagated songs at five distances, at two heights, and in two different habitat types. Counter to our prediction, we found no evidence that either form of soft song transmits differently than broadcast song when all were played loudly. If anything, soft songs transmitted more effectively when all songs were played quietly. Our results do not support one prediction made by the eavesdropping avoidance hypothesis, although the possibility remains that reduced amplitude alone is sufficient to reduce eavesdropping. The question of why warbled soft song differs in acoustic structure remains unresolved. Quiet aggressive signals are a puzzle because their meek form seems counter to their purpose—to threaten and intimidate rivals. One explanation for quiet signals is that reducing the signal’s transmission range reduces the costs imposed by eavesdroppers, which predicts that quiet signals will transmit through the environment poorly relative to louder, broadcast signals. We tested this prediction by playing song sparrow “soft songs” and “broadcast songs” at the same amplitudes and measured their transmission properties at different distances and heights, and in two habitats. We found that soft and broadcast songs did not transmit differently when played loudly, and soft songs transmitted slightly better when played softly. Our results do not support the idea that quiet signals are explained by eavesdropping avoidance, at least not in the song sparrow.

Eavesdropping avoidance and sound propagation: the acoustic structure of soft song

Many species use low-amplitude (soft) song during close range interactions with conspecifics, such as in aggressive encounters or courtship displays. It has been suggested that soft song is adapted to limit eavesdropping by conspecifics or predators through reduced signal transmission range. If so, other structural features of soft song, besides amplitude, should be adapted to reduce transmission. The soft songs of white-throated thrushes, Turdus assimilis, have properties expected to lower transmission, such as higher frequency and broader bandwidth relative to broadcast songs. We compared the transmission properties of broadcast and soft syllables using a sound propagation field experiment. When played at the same amplitude as broadcast song, soft song showed greater excess attenuation and blur ratios and lower signal-to-noise ratios. Lowering the frequency of soft syllables recovered similar transmission properties as those of broadcast syllables. Further analysis of spectral traits showed that excess attenuation values were mainly affected by minimum frequency and peak frequency, while blur ratio variation was predominantly affected by bandwidth, and signal-to-noise ratios were predicted by bandwidth and peak frequency. Additionally, soft song had more frequency overlap with background noise than broadcast song. These results support the eavesdropping hypothesis: aspects of the acoustic structure of soft signals in addition to low amplitude seem to have been shaped by selection to reduce transmission and avoid eavesdroppers.

Rock wrens preferentially use song types that improve long distance signal transmission during natural singing bouts

When animals are capable of producing variable signals they may preferentially use some signal types over others. Among songbirds, individuals are known to alter song type form and usage patterns in contest and mating situations, but studies have not examined how song choice improves signal efficacy during broadcast song. For this study we investigated rock wren Salpinctes obsoletus song type use rates during natural singing bouts. We tested three hypotheses for adaptive song use during broadcast song: 1) birds improve signal content by increasing the use of high quality songs, 2) birds optimize for signal propagation by preferentially using songs that transmit well, and 3) birds maintain energy by reducing the use of costly songs. The study included 19 058 songs sung by 12 individuals, each of which had a measured song repertoire of between 52 and 117 song types which were produced at highly variable rates. Results indicated that rock wrens did not preferentially sing song types with shorter durations or fewer frequency switches, as would be expected if they selected song types to minimize delivery costs. They also did not favor songs with more rapid trills or more frequency switches, as would be expected if they adjusted song use primarily to indicate quality. Focal birds did preferentially sing significantly longer songs with lower bandwidths, lower frequencies, and slower trill rates. Results suggest that natural broadcast singing patterns are shaped more by the benefits of long distance transmission than by the benefits of advertising performance ability or the costs of song production.

It's complicated: the association between songbird extrapair paternity and within-song complexity

Many songbird species are socially monogamous while exhibiting varying extrapair paternity frequencies. Song complexity, often subject to sexual selection, similarly varies across songbird taxa. Some species form highly complex songs whereas others produce simple songs. The basis of this variability, however, is unresolved. Because selection pressures generally favour the evolution of sexually selected characteristics reflecting male quality, such as song complexity, it should be subject to extrapair mate selection. We therefore predicted a positive association between extrapair paternity frequency and songbird song complexity. In addition, we predicted that broadcast (long-range) rather than interactive songs (short-range) would be more likely to contain sexually selected characteristics, such as higher complexity, especially in species with high extrapair paternity frequencies. This was tested using tui, Prosthemadera novaeseelandiae , a species with high extrapair paternity frequency. First, analyses on 78 songbird species indicated a significant positive association between extrapair paternity frequency and within-song complexity (the level of complexity within a species-specific song) but not between-song complexity (size of species-specific song or syllable repertoire), while no phylogenetic trait conservation was found. Additionally, our results suggested tui broadcast songs had higher song complexity than interactive songs. The findings in this study indicate extrapair mate selection may play a role in the evolution of within-song complexity in songbirds.

A Reassessment of the Distribution of Virginia’s Warbler in the Black Hills of South Dakota

virginia’s Warbler (Oreothlypis virginiae) reaches the northeastern limit of its breeding range in the southern Black Hills of South Dakota, where it is considered a species of conservation concern. this population occurs in pine–juniper–shrub habitat in several canyons in extreme western Custer County. additional such habitat occurs in the southern Black Hills south and east of the documented breeding populations, but these areas have received few systematic surveys, and whether virginia’s Warbler occupies them was uncertain. therefore, to define the species’ distribution in the South Dakota Black Hills more precisely, we surveyed with the aid of broadcast song and reviewed other reports. virginia’s Warblers occurred in appropriate habitats all along the southwestern front (approximately 30 km total) of the Black Hills in Custer County but did not occur in similar habitat along the southeastern front, approximately 25 km distant. the species’ relative abundance in previously and newly identified pine–juniper–shrub habitats was similar. virginia’s Warbler occurrence was positively associated with shrub cover (primarily mountain-mahogany, Cercocarpus montanus), pine overstory, and slopes of >15°. its association with the Spotted towhee (Pipilo maculatus) was negative, with the yellow-rumped Warbler (Setophaga coronata) tended toward positive, and with the Dusky flycatcher (Empidonax oberholseri) was variable (negative along the southwestern front but weakly positive across all sites). these data extend the documented breeding range of virginia’s Warbler in South Dakota by more than 20 km to the southeast. to clarify conservation priorities for this species at the northeastern limit of its range, future studies should delineate local and landscape-level characteristics of this population’s habitat more precisely and address its source–sink population dynamics. virginia’s Warbler (Oreothlypis virginiae) nests widely in mountainous regions of southwestern north america from southeastern idaho and southwestern Wyoming into southern arizona, new Mexico, and western texas (olson and Martin 1999). the species’ northeasternmost population is isolated in the southwestern Black Hills of South Dakota, separated by over 200 km from the next nearest breeding population in south-central Wyoming (Swanson et al. 2000). Breeding habitat occurs on mountain slopes and consists of dense, shrubby vegetation with taller plants interspersed or nearby (olson and Martin 1999). in various portions of the breeding range the shrubby vegetation may include chokecherry (Prunus virginiana), snowberry (Symphoricarpos spp.), currant (Ribes spp.), serviceberry (Amelanchier spp.), manzanita (Arctostaphylos spp.), scrub oak (Quercus gambelii), or mountain-mahogany (Cercocarpus montanus) (olson and Martin 1999). the taller vegetation may consist of pinyon pine (Pinus spp.), juniper (Juniperus spp.), ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), taller scrub oak, or aspen (Populus tremuloides) (olson and Martin 1999). virginia’s Warbler was first definitively recorded in South Dakota in 1997,

Reliability of the Brownish-flanked Bush Warbler’s soft song in male-male conflict

Soft song is a low-amplitude song produced by many birds. Recent studies have confirmed that soft song is an aggressive signal. For example, the Brownish-flanked Bush Warblers Cettia fortipes use soft song in male-male conflicts, particularly prior to attacks. Although stable signaling systems require that signals be honest on average, models predict that cheating is an acceptable strategy for some individuals or in some contexts. This study aimed to test the reliability of soft song as an aggressive signal in the brownish-flanked bush warbler. We used mounted specimens accompanied by broadcast songs or soft songs to simulate a male attempting to invade an existing territory. We found the mounted specimen that coupled playback of soft songs suffered more and quicker attacks from the territory owner and that the relationship between soft song and subsequent attack in the territory owner was far from perfect. We observed territory owners that both over-signaled (i.e., produced soft song but did not attack) and under-signaled (i.e., attacked without producing soft song). Under-signaling territory owners were relatively more commonly than were over-signaling territory owners, particularly in simulated intrusion that coupled playback of soft song with a mount specimen. We discuss the cost of producing soft song and the potential benefit of the unreliable use of soft song and propose a new hypothesis for under-signaling with soft song; i.e., under-signaling territory owners might benefit from taking the initiative in fights.

Is the Soft Song of the Brownish‐Flanked Bush Warbler an Aggressive Signal?

AbstractSoft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish‐flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species.

Soft song during aggressive interactions: Seasonal changes and endocrine correlates in song sparrows

It is well known that songbirds produce high amplitude songs (“broadcast songs”). Songbirds also produce low amplitude songs (“soft songs”) during courtship or territorial aggression in the breeding season. Soft songs are important social signals but have been studied far less than broadcast songs. To date, no studies have examined seasonal changes in soft song or its endocrine regulation. Here, in male song sparrows, we examined soft songs during a simulated territorial intrusion in the breeding season and non-breeding season. We also measured plasma testosterone and dehydroepiandrosterone (DHEA) levels in subjects immediately after the aggressive encounter. The total number of songs produced (broadcast+soft songs) did not vary between seasons. However, there was a dramatic increase in the percentage of soft song in the non-breeding season. Further, the percentage of soft song was negatively correlated with plasma testosterone levels in the non-breeding season. There were seasonal differences in the acoustic structure of two major elements of soft song, trills and buzzes. The minimum frequency of trills was lower in the non-breeding season, and the element repetition rate of buzzes was lower in the non-breeding season. To our knowledge, this is the first study to (1) examine soft songs outside of the breeding season and (2) to identify endocrine correlates of soft songs, which are important social signals in songbirds.

The receiver-dependent cost of soft song: a signal of aggressive intent in songbirds

Social costs are one mechanism whereby reliability in signalling systems can be maintained. We measured the strength of aggressive response to territorial playback to ask whether the reliability of ‘soft song’, a strongly aggressive signal in the song sparrow, Melospiza melodia, is enforced by a social cost in the form of the receiver's aggressive response. We also asked whether this cost is imposed by all receivers, or whether a differential response is found primarily or exclusively among the most aggressive subjects. We first measured the strength of each male's aggressive response to playback on his territory, and then tested his responses to ‘warbled’ soft song and to broadcast song playbacks. While we found substantial variation in individual aggressiveness, nearly all males responded more strongly to warbled soft songs. Thus we provide evidence that warbled soft song imposes a social cost in the form of receiver retaliation, and provide a possible explanation for how the signal's reliability is maintained. Questions about soft song remain, notably why selection should favour low amplitude in vocal signals of aggression in songbirds.

Song Amplitude of Rival Males Modulates the Territorial Behaviour of Great Tits During the Fertile Period of Their Mates

AbstractBird song is a widely used model in the study of sexual selection. Variation in the expression of sexually selected traits is thought to reflect variation in male genetic and/or phenotypic quality. Vocal amplitude is a song parameter that has received little attention in the context of sexual selection, but there is some evidence that the intensity of bird song affects female preferences. Here, we tested whether the amplitude of broadcast song plays a role in male–male competition. We used song playback with varying song amplitude (within the natural amplitude range of the species) and a dummy bird taxidermy to simulate territorial intrusions in the great tit, Parus major, during the fertile period of the female and measured the response of the local male. The results show that playback amplitude significantly affected the subjects’ behaviour: after approaching to within 25 m around the loudspeaker, territorial males stayed longer within that perimeter after the playback of high‐amplitude songs compared with low‐amplitude songs. Our findings add to the small but growing body of evidence suggesting that vocal amplitude may be a sexually selected song trait.

Effects of personality on territory defence in communication networks: a playback experiment with radio-tagged great tits

Individuals often differ consistently in behaviour across time and contexts, and such consistent behavioural differences are commonly described as personality. Personality can play a central role in social behaviour both in dyadic interactions and in social networks. We investigated whether explorative behaviour, as proxy of personality of territorial male great tits (Parus major), predicts their own and their neighbours' territorial responses towards simulated intruders. Several weeks prior to playback, subjects were taken from the wild to test their exploratory behaviour in a standard context in the laboratory. Exploratory behaviour provides a proxy of personality along a slow-fast explorer continuum. Upon release, males were radio-tracked and subsequently exposed to interactive playback simulating a more or a less aggressive territorial intruder (by either overlapping or alternating broadcast songs with the subjects' songs). At the same time, we radio-tracked a neighbour of the playback subject. Male vocal responses during playback and spatial movements after playback varied according to male explorative behaviour and playback treatment. Males with lower exploration scores approached the loudspeaker less, and sang more songs, shorter songs and songs with slower element rates than did males with higher exploration scores. Moreover, neighbour responses were related to the explorative behaviour of the subject receiving the playback but not to their own explorative behaviour. Our overall findings reveal for the first time how personality traits affect resource defence within a communication network providing new insights on the cause of variation in resource defence behaviour.