Song Playback Research Articles

Early acoustic experience alters genome-wide methylation in the auditory forebrain of songbird embryos

Early exposure to salient cues can critically shape the development of social behaviors. For example, both oscine birds and humans can hear and learn to recognize familiar sounds in ovo and in utero and recognize them following hatching and birth, respectively. Here we demonstrate that different chronic acoustic playbacks alter genome-wide methylation of the auditory forebrain in late-stage zebra finch (Taeniopygia guttata) embryos. Within the same subjects, immediate early gene activation in response to acute con- or heterospecific song exposure is negatively correlated with methylation extent in response to repeated daily prior exposure to the same type of stimuli. Specifically, we report less relative global methylation following playbacks of conspecific songs and more methylation following playbacks of distantly-related heterospecific songs. These findings offer a neuroepigenomic mechanism for the ontogenetic impacts of early acoustic experiences in songbirds.

Song divergence indicates an unclear relationship between the Neotropical and Nearctic Horned Larks

BackgroundSome studies have indicated that the Horned Larks (Eremophila alpestris) should be considered as a species complex. Recently it split into four species or clades and seven subclades based on genetic, morphological, and biogeographic data. However, other aspects like song divergence have not been studied and several subspecies have not been evaluated, leading to important information gaps in this group of birds. In this work, we aimed to assess the differences in song traits and playback response between the Nearctic subclade and the Neotropical or Colombian subspecies E. a. peregrina.MethodsWe compared six song traits between these groups and performed field playback experiments, to test the response of the Neotropical larks to both songs. We tested the difference in the variables for separate as well as by principal component analysis (PCA).ResultsWe found significant differences (p < 0.05) in the individual song traits and the PCA analysis between the two groups. Further, the PCA analysis showed a clearer divergence of the Neotropical songs in comparison to the Nearctic songs of different locations within North America. Similarly, the playback analysis showed a significantly lower response of E. a. peregrina to the songs of the Nearctic larks.ConclusionsBesides this song divergence, there are important ecological and biogeographic differences between the Neotropical and Nearctic Horned Larks, that indicate an unclear relationship between these two groups. Thus, further morphological and genetic studies are required to clarify the taxonomy of the Neotropical Horned Lark and define if they share the same evolutionary history as the other subspecies of the Nearctic subclade.

Social information affects prospecting, but not settlement, by Black‐and‐white Warblers (Mniotilta varia)

Birds use social as well as environmental cues to inform their habitat selection decisions. By manipulating social cues with song playbacks, biologists can influence where individuals search for breeding territories, which could be useful for conservation. Yet before we can predict how birds will respond to playback treatments, we must first understand how they integrate social cues with information about habitat quality at different stages in the habitat selection process. In this experiment, we examined whether vegetation structure and/or social cues affected Black‐and‐white Warbler Mniotilta varia abundance at three study areas that differed in habitat quality. We monitored Black‐and‐white Warbler habitat use across the breeding season, from the early prospecting period until after settlement decisions were made. During seasons without playback treatments, Black‐and‐white Warbler abundance was positively associated with levels of understorey vegetation cover. We then played Black‐and‐white Warbler songs daily for 5–6 weeks at selected survey sites at all study areas. We found that the model‐predicted abundance of Black‐and‐white Warblers was nearly three times greater at playback sites than at control sites during the prospecting period. During seasons with playbacks, understorey vegetation cover was no longer associated with Black‐and‐white Warbler abundance, indicating that individuals prioritized social information when searching for breeding territories. However, during the post‐settlement period, neither playbacks nor levels of understorey vegetation cover were associated with increased abundance, suggesting that playback treatments did not influence final breeding territory choice. We also found no difference in abundance between playback and control sites at a study area that represented low‐quality habitat, which suggests that playbacks should not induce maladaptive site selection.

Territorial males do not discriminate between local and novel plumage phenotypes in a tropical songbird species complex: implications for the role of social selection in trait evolution

Whether novel traits involved in animal communication are favored or not by social selection depends on how receivers respond to them. If alternative traits arise at different locations or the same traits are perceived differently, then populations may diverge even when occupying similar environments. Aggressiveness towards bearers of novel versus familiar traits is informative about how male-male competition may drive phenotypic evolution, yet few studies have tested the function of signaling traits in social selection across populations. We assessed the role of a black pectoral band during territorial contests in two allopatric species of Neotropical passerine birds in the genus Arremon either having or lacking this plumage trait. Field experiments using taxidermic mounts and playback of conspecific songs revealed that males of both species were equally aggressive towards phenotypes bearing or lacking a pectoral band. Although evaluating physiological and social costs of bearing alternative traits and assessing female preferences is required to further examine the roles of social and sexual mechanisms in the evolution of plumage and geographic variation, our results indicate that social selection via male-male interactions is an unlikely driver of phenotypic divergence among populations of Arremon. Social selection via intrasexual competition for resources may drive phenotypic divergence and population differentation in animals, but few studies have tested predictions of this hypothesis by examining how alternative traits varying geographically are perceived in contexts of male-male competition. We assessed the behavioral response of territorial males in two species of Neotropical songbirds to taxidermic mounts having or lacking a black pectoral band, a geographically variable plumage trait. Irrespective of their own phenotype, males of both species were similarly aggressive to potential intruders bearing or lacking the pectoral band. In contrast with work suggesting male-male interactions may mediate trait evolution, our results indicate that pectoral bands in this system are unlikely targets of social selection via contests in which males compete for territories, and call for studies assessing long-term costs of bearing alternative traits or female choice as selective forces driving phenotypic evolution.

Female signal jamming in a socially monogamous brood parasite

Acoustic signalling is vital to courtship in many animals, yet the role of female vocalizations is understudied. Here, we combine observational and experimental methods to assess the courtship function of the female chatter call in brown-headed cowbirds, Molothrus ater. While the chatter call is likely multifunctional, it is frequently used in social interactions and overlapping duets with males during the breeding season. Based on a combination of focal- and scan-sampling data from large naturalistic aviaries, we did not find support for the hypothesis that the chatter call elicits male attention or encourages continued courtship. However, we did find evidence that the chatter call plays a role in pair bond formation, as females preferentially chattered in response to songs from pair-bond males in the 2 weeks leading up to the median date of first copulation. Females were less selective in male-directed chatter use after copulations began. We also found support for the hypothesis that chatter is used to signal-jam male songs. Frame-by-frame video analysis revealed that the majority of female chatter calls were tightly time-locked to song, occurring less than 500 ms after male vocal onset. To test the effect of signal jamming on male song potency, we designed a laboratory experiment in which male song playbacks were jammed by various recorded stimuli. Natural chatter calls more effectively reduced female copulatory responses to song than high-pass filtered chatter calls, suggesting that the low frequencies in natural chatter (2-4 kHz) are important for interfering with male song and reducing its potency. Our results suggest that sexual conflict is operating in cowbird courtship, with signal jamming serving as a mechanism by which females guard, resist or select their mates. We also discuss ways in which cowbird vocal interactions may function cooperatively to coordinate reproduction or transition females into breeding condition.

Leptin regulates song effort in Neotropical singing mice (Scotinomys teguina)

Sexual signals are often elaborate, even spectacular, behaviours. The reproductive rewards for successful display are great, but so are the potential costs. These costs include not only the resources needed to produce a display, but also resources required if the display evokes attack from a rival or predator. To maximize payoff, individuals must monitor both internal and external cues to adjust display effort. We know surprisingly little about how these competing demands are balanced. Leptin, a hormone secreted by adipose tissue, regulates energy allocation to functions as diverse as feeding, sleep, reproduction and immunity. Despite evidence that leptin influences reproductive trade-offs, its role as a putative regulator of courtship display is poorly understood. Here we examine the use of interoceptive and exteroceptive cues to modulate display effort in Alston's singing mouse, Scotinomys teguina. We manipulated individual perception of energy balance through intraperitoneal injection of exogenous leptin, and we manipulated social context through playback of conspecific song. Leptin-injected mice responded with song to playback more frequently and more quickly than saline-injected controls. Although leptin seems to promote increased song effort, we found that leptin also reduced song duration. Song effort increased after leptin injection and playback of conspecific songs. Understanding the mechanisms by which animals respond to internal and external cues broadens our understanding of context-dependent display as well as behavioural plasticity more generally.

Dinner and a show: The role of male copulatory courtship song and female blood-feeding in the reproductive success of Lutzomyia longipalpis from Lapinha, Brazil

Lutzomyia longipalpis is the main vector of visceral Leishmaniasis in the Americas and is composed of a species complex. Males of this sand-fly produce acoustic signals during copulation and different patterns are observed among Brazilian populations. Such acoustic signals are commonly involved in species recognition. However, since the song is only produced during copulation it is not clear how it affects mating success or contributes to sexual isolation. Another aspect that may affect reproductive success is the presence of food. Since hematophagy is such an important aspect of L. longipalpis biology, we wanted to test if blood-feeding can influence the reproductive behaviour of this insect. We performed crossing experiments removing males' wings (silencing them) and playing back either the homo-specific or the hetero-specific song to either unfed or blood-fed females. Our results showed that both songs and blood-feeding affect insemination success, but not the frequency of copulation. In trials where females were not blood-fed song clearly affected insemination; males with wings, and males with homo-specific song playback had a higher insemination success than wingless males (no song) and trials with hetero-specific song. Blood-feeding females prior to the trials increased insemination in all groups including the control group which suggests that mating happens simultaneously with, or immediately after, the blood meal. Blood-fed females also seemed to discriminate less against the wrong song or the lack of song (wingless) one day after feeding, however trials with the correct song still had higher insemination rates. Altogether, our results show that both the male copulatory courtship songs and female blood-feeding are important for reproductive success and as such are important components of the sexual behaviour of L. longipalpis.

White-handed gibbons discriminate context-specific song compositions

White-handed gibbons produce loud and acoustically complex songs when interacting with their neighbours or when encountering predators. In both contexts, songs are assembled from a small number of units although their composition differs in context-specific ways. Here, we investigated whether wild gibbons could infer the ‘meaning’ when hearing exemplars recorded in both contexts (i.e. ‘duet songs’ vs. ‘predator songs’). We carried out a playback experiment by which we simulated the presence of a neighbouring group producing either its duet or a predator song in order to compare subjects’ vocal and locomotor responses. When hearing a recording of a duet song, subjects reliably responded with their own duet song, which sometimes elicited further duet songs in adjacent groups. When hearing a recording of a predator song, however, subjects typically remained silent, apart from one of six groups which replied with its own predator song. Moreover, in two of six trials, playbacks of predator songs elicited predator song replies in non-adjacent groups. Finally, all groups showed strong anti-predator behaviour to predator songs but never to duet songs. We concluded that white-handed gibbons discriminated between the two song types and were able to infer meaning from them. We discuss the implications of these findings in light of the current debate on the evolutionary origins of syntax.

Ontogeny of vocal learning in a hummingbird

Hummingbirds have evolved to learn song from conspecifics independently of other bird clades that show this behaviour, such as parrots and oscine passerines. Little is known about how vocal learning occurs in hummingbirds. To determine the conditions necessary and sufficient for learning, we raised young Costa's hummingbirds, Calypte costae, in isolation in two experiments. The first experiment tested whether three pairs of males, raised either in silence or with only acoustic exposure to song, would produce wild-type song. They did not: each pair instead produced ‘isolate’ songs dissimilar to wild-type song. Each pair produced a unique isolate song with subtle differences from other pairs. Thus, exposure to song alone is insufficient to trigger learning. The second experiment tested whether individually housed males would learn songs when exposed to a live male model plus playback of song (1 h/day, 3 days/week, for 3 months). Seven of eight birds that heard Costa's-like songs learned to sing their tutor song. Each individual produced song that matched idiosyncratic features of the individual songs played to them, demonstrating attention to, and learning of the exact acoustic stimuli received. Two control birds exposed to acoustically dissimilar Anna's hummingbird, Calypte anna, song developed isolate song. Thus, exposure to species-specific song with a conspecific male is sufficient to trigger learning. The sensory phase began after fledging, around 23 days posthatch, and the sensorimotor phase began around 50 days posthatch, when singing also began. Song crystallization occurred approximately 125 days posthatch. Costa's also appear to be statistical learners; they learn to sing the songs they hear most often. Hummingbird song ontogeny appears to be similar to song ontogeny in passerines, despite its convergent origin.

Epi-Intra neural probes with glassy carbon microelectrodes help elucidate neural coding and stimulus encoding in 3D volume of tissue

Objective. In this study, we demonstrate practical applications of a novel 3-dimensional neural probe for simultaneous electrophysiological recordings from the surface of the brain as well as deep intra-cortical tissue. We used this 3D probe to investigate signal propagation mechanisms between neuronal cells and their responses to stimuli in a 3D fashion. Approach. This novel probe leverage 2D thin-film microfabrication technique to combine an epi-cortical (surface) and an intra-cortical (depth) microelectrode arrays (Epi-Intra), that unfold into an origami 3D-like probe during brain implantation. The flexible epi-cortical component conforms to the brain surface while the intra-cortical array is reinforced with stiffer durimide polymer layer for ease of tissue penetration. The microelectrodes are made of glassy carbon material that is biocompatible and has low electrochemical impedance that is important for high fidelity neuronal recordings. These recordings were performed on the auditory region of anesthetized European starling songbirds during playback of conspecific songs as auditory stimuli. Main results. The Epi-Intra probe recorded broadband activity including local field potentials (LFPs) signals as well as single-unit activity and multi-unit activity from both surface and deep brain. The majority of recorded cellular activities were stimulus-locked and exhibited low noise. Notably, while LFPs recorded on surface and depth electrodes did not exhibit strong correlation, composite receptive fields (CRFs)—extracted from individual neuron cells through a non-linear model and that are cell-dependent—were correlated. Significance. These findings demonstrate that CRFs extracted from Epi-Intra recordings are excellent candidates for neural coding and for understanding the relationship between sensory neuronal responses and their stimuli (stimulus encoding). Beyond CRFs, this novel neural probe may enable new spatiotemporal 3D volumetric mapping to address, with cellular resolution, how the brain coordinates function.

Vocal recognition suggests premating isolation between lineages of a lekking hummingbird

AbstractSpecies with genetically differentiated allopatric populations commonly differ in phenotypic traits due to drift and/or selection, which can be important drivers of reproductive isolation. Wedge-tailed sabrewing (Campylopterus curvipennis) is a species complex composed of three genetically and acoustically differentiated allopatric lineages that correspond to currently recognized subspecies in Mexico: C. c. curvipennis (Sierra Madre Oriental), C. c. pampa (Yucatán Peninsula), and C. c. excellens (Los Tuxtlas). Although excellens is taxonomically recognized as a distinct species, there is genetic evidence that lineages excellens and curvipennis have diverged from each other later than pampa. In this study, we experimentally tested C. c. curvipennis song recognition as a major factor in premating reproductive isolation for lineage recognition. To this end, we conducted a song playback experiment to test whether territorial males of one C. c. curvipennis lek discriminate among potential competitors based on male songs from the three lineages. Males of curvipennis responded more aggressively to songs of their own lineage and excellens, than to songs of the most divergent lineage pampa, as evidenced by significant differences in a variety of intensity and latency response variables. This indicate that the pampa male song does not represent a competitive threat as curvipennis and excellens songs, in which divergence and song recognition represent premating reproductive isolation between these isolated lineages. However, the acoustic limits between curvipennis and excellens might be attenuated by gene flow in case of secondary contact between them, despite the strong and relatively rapid divergence of their sexually selected song traits.

Response of Male Hawaii Elepaio Chasiempis sandwichensis to Conspecific Songs: A Small-Scale Playback Study

Las aves paseriformes aprenden sus cantos principalmente a traves de la transmision cultural. Sin embargo, la fragmentacion del habitat puede provocar una variacion cultural en el aprendizaje de cantos dando lugar a restricciones en la transmision de informacion cultural, incluyendo interacciones acusticas. En este estudio, nuestro objetivo es evaluar la respuesta individual a vocalizaciones de la misma especie dentro de dos poblaciones diferentes, asi como entre ambas poblaciones. Para ello, utilizamos reproducciones de cantos del monarca elepaio Chasiempis sandwichensis en un paisaje fragmentado que se encuentra en la ladera noreste del volcan Mauna loa (Isla de Hawai, EE.UU.). Evaluamos la respuesta de los machos de monarca elepaio a los cantos grabados en su misma poblacion, asi como en una poblacion diferente. Tambien comparamos vocalizaciones entre ambas poblaciones para evaluar diferenciacion acustica. Nuestros resultados indican divergencias comportamentales en la respuesta al canto de esta especie a pequena escala, asi como diferencias significativas en rasgos acusticos. Sin embargo, contrariamente a lo que se esperaba, los individuos de monarca elepaio de ambas poblaciones no variaron en su patron de respuesta a los cantos en funcion de su origen. Esto sugiere que la diferenciacion acustica puede no ser lo suficientemente fuerte como para dar lugar a una divergencia comportamental en la respuesta de los individuos de monarca elepaio, a pesar de la existencia de diferencias entre los rasgos acusticos de ambas poblaciones.

The Role of Nestling Acoustic Experience in Song Discrimination in a Sparrow

Oscine songbirds are an ideal system for investigating how early experience affects vocal behavior. Young songbirds face a challenging task: how to recognize and selectively learn only their own species’ song, often during a time-limited window. Because birds are capable of hearing birdsong very early in life, early exposure to song could plausibly affect recognition of appropriate models; however, this idea conflicts with the traditional view that song learning occurs only after a bird leaves the nest. Thus, it remains unknown whether natural variation in acoustic exposure prior to song learning affects the template for recognition. In a population where sister species, golden-crowned and white-crowned sparrows, breed syntopically, we found that nestlings discriminate between heterospecific and conspecific song playbacks prior to the onset of song memorization. We then asked whether natural exposure to more frequent or louder heterospecific song explained any variation in golden-crowned nestling response to heterospecific song playbacks. We characterized the amount of each species’ song audible in golden-crowned sparrow nests and showed that even in a relatively small area, the ratio of heterospecific to conspecific song exposure varies from 0 to 20%. However, although many songbirds hear and respond to acoustic signals before fledging, golden-crowned sparrow nestlings that heard different amounts of heterospecific song did not behave differently in response to heterospecific playbacks. This study provides the first evidence that song discrimination at the onset of song learning is robust to the presence of closely related heterospecifics in nature, which may be an important adaptation in sympatry between potentially interbreeding taxa.

Song-type switching rate in the chaffinch carries a message during simulated intrusion

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.Significance statementUsing playback experiments, we show that birds’ responses to simulated territorial intrusion vary not only with the type of stimulus but also with the tested males’ spontaneous song output. We found that, from the perspective of the song receiver, variation in switching rate carries a message for territorial chaffinches. Our findings add a new example of agonistic signaling in which territorial males exhibit a stronger response toward rivals singing with lower song-type switching rate, which up to now has only been demonstrated in a few species. Moreover, our results show that a male’s response to playback could be predicted using his song output. This may be associated with motivation and willingness to escalate a conflict and could possibly also indicate a male’s quality.

Fine‐scale observations of spatio‐spectro‐temporal dynamics of bird vocalizations using robot audition techniques

AbstractEcoacoustics needs sophisticated acoustic monitoring tools to extract a wide level of features from an observed mixture of sounds. We have developed a portable acoustic monitoring system called ‘HARKBird’ which consists of a laptop PC and an inexpensive commercial microphone array with the robot audition software HARK. HARKBird can extract acoustic events in a recording, and we can obtain the begin and end timings, the spatial information (e.g., position or direction from the microphone array), and the spectrogram of the sound separated from the original recording. In this study, we report how robot audition techniques contribute to monitoring spatio‐spectro‐temporal dynamics of bird behaviors, using an extended and minimal system based on multiple microphone arrays. The dimension reduction of separated sounds is important to integrate the information from multiple microphone arrays. As a dimension reduction algorithm, we use t‐SNE to help manual annotation of each sound and to generate the vocalization distribution automatically. We conduct playback experiments to Spotted Towhee (Pipilo maculatus) to simulate different cases of territorial intrusions (song/call/no playback). Our hypothesis in playback experiments is that playback of conspecific vocalizations would invoke aggressive responses of males against song playbacks and the effects would be more prominent than those of call playbacks. Our primary aim is to test whether our system can extract the necessary information on the aggressiveness of target individuals to examine our hypothesis. We show the system with manual annotation of vocalizations can extract their different spatio‐spectro‐temporal dynamics in different conditions, which supported our hypothesis. We also consider the spectral affinity‐based automatic matching of localized sounds from different microphone arrays. The relative number of localized songs depending on the playback conditions reflected a similar trend to those in the manual approach, implying that we can grasp the long‐term dynamics of vocalizations without costly annotations.

Singing under glass: rapid effects of anthropogenic habitat modification on song and response behaviours in an isolated house sparrow Passer domesticus population

Anthropogenic noise pollution and the introduction of novel infrastructure can impose strong selective pressures on avian communication by affecting the efficacy with which acoustic signals are transmitted and received. Many species have now been shown to sing at higher frequencies in noisy urban environments. However, few studies have investigated the effects of signal modification on the response behaviours of receivers, and fewer still have been able to indicate the timescale over which these changes in pitch have occurred. We compare vocal communication between house sparrows Passer domesticus that reside within the world's largest, single‐span glasshouse (completed in the year 2000), and house sparrows directly outside this glasshouse, in open farmland. The glasshouse contrasts both acoustically and physically with the external environment, low frequency background noise being significantly louder inside than outside. We show that minimum song frequency was significantly higher inside the glasshouse than in surrounding farm habitat. Using song playback, we also found that birds within the glasshouse reacted more strongly to playbacks from the glasshouse habitat than they did to playback of song from farm birds outside. The degree of difference in frequency is similar to that shown for other bird species between urban and rural environments, demonstrating that such behavioural differences may arise over a relatively short time period (14 yr in this case).

Heterospecific song quality as social information for settlement decisions: an experimental approach in a wild bird

Assessing local habitat quality via social cues provided by conspecific or heterospecific individuals sharing the same needs is a widespread strategy of social information use for breeding habitat selection. However, gathering information about putative competitors may involve agonistic costs. The use of social cues reflecting local habitat quality acquired from a distance, such as acoustic cues, could therefore be favoured. Bird songs are conspicuous signals commonly assumed to reliably reflect producer quality, and thereby local site quality. Birds of various species have been shown to be attracted to breeding sites by conspecific and heterospecific songs, and to use conspecific song features as information on producer (and by extension habitat) quality. Whether they can do the same with heterospecific song features, and whether this depends on the individual's own phenotype and especially its competitive ability, remains unknown. We used a playback experiment in a wild population of collared flycatchers, Ficedula albicollis, a species known to eavesdrop on the presence and performance of dominant great tits, Parus major. We tested whether flycatchers, whose aggressiveness was experimentally assessed, preferred to settle near playback of a high-quality great tit song (i.e. song with large repertoire size, long strophes, high song rate), a low-quality great tit song or a chaffinch song (control). Among old females, aggressive ones preferred to settle near playback of high-quality tit song and avoided playback of low-quality tit song, while less aggressive females preferred to settle near playback of low-quality tit song. Male personality or age did not influence settlement decisions. This shows that collared flycatcher females use great tit song quality features as information for settlement decisions, although this depended on their own competitive ability and/or previous experience with great tit songs. Our study therefore further illustrates the complex condition-dependent use of heterospecific social information for breeding habitat selection.

Behavioural response of Eurasian Blackcaps to acoustically simulated conspecific and heterospecific male intruders

Interspecific territoriality can frequently be observed in the animal kingdom, including birds. One important factor driving the degree of interspecific territoriality is competition for resources. Other influential factors are, for instance, population density, phylogenetic relatedness, fighting asymmetries, and shared predation. Although the degree of competition is usually a composite of several factors potentially influencing competition, it is possible to determine the degree of competition without knowing all influential factors and their importance. In line with this, we used the strength of behavioural interactions between species under standardized experimental conditions. In particular, we investigated the degree of interspecific competition using the territorial song of male Eurasian Blackcaps (Sylvia atricapilla) as a low-risk response variable and the crossing flights and nearest approach distance to an intruder as high-risk defence behaviours. To simulate an interspecific intruder, we used male song playbacks of phylogenetic-related and more or less coexisting species. In line with our predictions, we found territorial defence to be most intense against conspecifics (positive control) and virtually non-existent against the allopatric Subalpine Warblers (S. cantillans) (negative control). In terms of the defence reaction to sympatric interspecific intruders, the response seemed strongest in relation to the Garden Warbler (S. borin) and weakest in relation to the Barred Warbler (S. nisoria). Our results further show that the vegetation characteristics of a territory influence behavioural responses to intruders, but only in relation to low-risk defence.

Operant Conditioning Task to Measure Song Preference in Zebra Finches.

An operant conditioning paradigm is used to test the song preference of female zebra finches. Finches are placed in a two-chambered cage with a connecting opening and indicate their preference for a song by landing on a perch within each chamber. By interrupting the infrared beam from a photoelectric sensor above each perch, the bird activates the playback of a song through a speaker located on each side of the cage. Freely available software is used to trigger the song playback from each perch. To determine the song preference of each animal, her chamber preference is first identified by triggering no song playback when she lands on each perch. This chamber preference is then compared to her song preference. A minimum activity threshold is set to ensure the preference is real. Using this method, we show that paired females prefer the song of their partner. This method was used to understand the contribution of dopamine to the formation and maintenance of song preference.

Theoretical Review: The Protection of Music Copyrights in the Radio

Playback of music or songs on the radio has the potential to infringe the copyright songwriters. Based on the applicable legal provisions, namely Law Number 28 the Year 2014 concerning Copyrights, the songwriter is the copyright owner of music which is protected by law. Therefore, parties who take advantage of music must obtain permission from the copyright owner. Radio companies should get permission from the copyright owner to play the music on their radio station. However, it is difficult to oversee the playback of the music on the radio. In this context, a collective management agency (CMA) emerges, but the presence of a CMA is not mandatory or optional. Therefore, this paper does not involve CMA. In this regard, legal issues arise, namely how to protect music copyrights according to applicable law to attain legal certainty. This paper is a theoretical study of legal theory or legal doctrine relating to the rights of songwriters. In legal science or jurisprudence it is not clearly distinguished between legal doctrine and legal theory. In discussing this issue, firstly it will be discussed about the meaning and types of music copyrights. Next, it will be discussed about the legal construction or legal framework of music copyrights. Based on theoretical studies, songwriters have various rights with specific characteristics so that the treatments must also be accurate. The legal construction of music copyrights is intertwined in a network of legal binding that is influenced by subject and object factors. The subjects involved are interconnected to use the music as its object. The legal relationship between subjects is mutually beneficial or mutual symbiosis. Meanwhile, music as objects is a flexible commodity. Therefore, airing music on the radio is in doubt to be categorized as copyright infringement.