Song Playback Research Articles

Effectiveness of Artificial Song Playback on Influencing the Settlement Decisions of an Endangered Resident Grassland Passerine

Abstract. Social information in the form of songs, calls, or other overt behaviors may assist birds in assessing the quality of potential breeding habitat by providing direct public information about a site's quality or by providing indirect cues (e.g., the presence of conspecifics) that may be used to infer its quality. Broadcast of song has been used to demonstrate the influence of conspecific cues on the decisions of migratory passerines to settle; however, there is currently a dearth of information regarding resident species. We tested the influence of conspecific attraction and the effectiveness of song playback on an endangered resident of grassland, the Cape Sable Seaside Sparrow (Ammodramus maritimus mirabilis). We broadcast recorded song over large areas of suitable breeding habitat in the Florida Everglades in an attempt to influence the settlement of male sparrows during territory establishment. Our analyses included the creation of a qualitative sound map that formed a basis for measuring the ...

Canyon wrens alter their songs in response to territorial challenges

Many animals use low frequency and harsh sounds in aggressive contexts. Low frequencies are correlated with body size in some species, and thus can provide an indication of fighting ability. Because of this, low frequencies and harsh sounds may also indicate aggressive intent and motivation to attack. We tested for facultative adjustment of vocal behaviour in canyon wrens, Catherpes mexicanus , by using playbacks to simulate territorial intrusions. Thirteen territory-holding wrens were exposed to playback of typical conspecific songs which did not include harsh elements. Territory holders increased song rate in response to simulated intrusions, altered song type usage and altered some song sound frequency parameters. Birds singing in response to playbacks did not adjust the highest frequencies or the frequencies with maximum power in their songs, but they significantly lowered the lowest song frequencies and were more likely to append harsh notes to the ends of their songs. Results match predictions of the motivation-structural hypothesis, and suggest that canyon wrens alter their songs in multiple ways when faced with conspecific territorial intrusion. ► We tested predictions of the motivation-structural hypothesis in canyon wrens. ► We also tested whether wrens use low-frequency sounds as signals of aggression. ► Territory-holding canyon wrens changed their songs in response to playback of conspecific song. ► They used lower song frequencies and harsh notes more often following simulated territorial intrusions. ► Ours is the first study to experimentally demonstrate facultative song adjustment in a passerine.

Does mating experience of male house crickets affect their behavior to subsequent females and female choice?

Male mating experience was shown to play an important role in settling conflicts between males; however, little is known about whether and how prior access to females influences male behavior during intersexual interactions and female choice itself. Here, I experimentally test this relationship in the house cricket (Acheta domesticus) by combining one-on-one interaction between the male and female with direct comparison of males by the female, but precluding aggression between males. I found that solitary males were more active during subsequent courtship displays than paired males, suggesting the detrimental effect of mating on courtship performance. At the same time, females spent significantly more time close to solitary males or playbacks of male's natural courtship songs, and responded positively to the condition of males, ignoring body size of males. In contrast, females responded similarly to computer-modified playbacks of courtship songs of solitary and paired males with standardized rate of phrases and amplitudes; however, when females were additionally allowed to contact with anesthetized males they spent more time close to bigger males, irrespective of the acoustic parameters of courtship songs. These results show that although females were able to differentiate between many behavioral and morphological characteristics of males, including voluntary and intrinsic ones, they preferred traits conditional upon the costliness of male's displays. In addition, mating experience appeared to be a crucial factor in the choice of a particular costly mating strategy by males.

Comparisons of different methods to train a young zebra finch (Taeniopygia guttata) to learn a song

Like humans, oscine songbirds exhibit vocal learning. They learn their song by imitating conspecifics, mainly adults. Among them, the zebra finch (Taeniopygia guttata) has been widely used as a model species to study the behavioral, cellular and molecular substrates of vocal learning. Various methods using taped song playback have been used in the laboratory to train young male finches to learn a song. Since different protocols have been applied by different research groups, the efficiency of the studies cannot be directly compared. The purpose of our study was to address this problem. Young finches were raised by their mother alone from day post hatching (dph) 10 and singly isolated from dph 35. One week later, exposure to a song model began, either using a live tutor or taped playback (passive or self-elicited). At dph 100, the birds were transferred to a common aviary. We observed that one-to-one live tutoring is the best method to get a fairly complete imitation. Using self-elicited playback we observed high inter-individual variability; while some finches learned well (including good copying of the song model), others exhibited poor copying. Passive playback resulted in poor imitation of the model. We also observed that finches exhibited vocal changes after dph 100 and that the range of these changes was negatively related to their imitation of the song model. Taken together, these results suggest that social aspects are predominant in the success outcome of song learning in the zebra finch.

Soft song is a reliable signal of aggressive intent in song sparrows

Animals frequently use signals to modulate aggressive interactions. Establishing that a signal is aggressive or threatening requires demonstrating that it is more commonly used in agonistic contexts, that it predicts subsequent aggressive behaviors by the sender, and that receivers respond differently to this signal. Like many birds, song sparrows (Melospiza melodia) produce a low-amplitude “soft song” vocalization that has been hypothesized to be an aggressive signal. Soft song meets the first two criteria, but previous research has failed to demonstrate that soft song provokes aggression or that receivers even perceive soft song differently from normal loud song. We used a playback experiment with taxidermic mount presentation to test whether territorial male song sparrows respond differently to loud and soft song playbacks. Subjects reacted more strongly to the soft song playback by approaching the mount more closely, increasing wing wave displays, and increasing the proportion of their own songs that were soft songs, with further trends toward increasing the number of flights and attacks. These results confirm that soft song is a conventional signal of aggression in song sparrows and that increased receiver retaliation maintains its reliability.

Robust behavioral effects of song playback in the absence of testosterone or corticosterone release

Some species of songbirds elevate testosterone in response to territorial intrusions while others do not. The search for a general explanation for this interspecific variation in hormonal response to social challenges has been impeded by methodological differences among studies. We asked whether song playback alone is sufficient to bring about elevation in testosterone or corticosterone in the dark-eyed junco (Junco hyemalis), a species that has previously demonstrated significant testosterone elevation in response to a simulated territorial intrusion when song was accompanied by a live decoy. We studied two populations of juncos that differ in length of breeding season (6–8 vs. 14–16weeks), and conducted playbacks of high amplitude, long-range song. In one population, we also played low amplitude, short-range song, a highly potent elicitor of aggression in juncos and many songbirds. We observed strong aggressive responses to both types of song, but no detectable elevation of plasma testosterone or corticosterone in either population. We also measured rise in corticosterone in response to handling post-playback, and found full capacity to elevate corticosterone but no effect of song class (long-range or short-range) on elevation. Collectively, our data suggest that males can mount an aggressive response to playback without a change in testosterone or corticosterone, despite the ability to alter these hormones during other types of social interactions. We discuss the observed decoupling of circulating hormones and aggression in relation to mechanisms of behavior and the cues that may activate the HPA and HPG axes.

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.

Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback

The Challenge Hypothesis postulates that male vertebrates can respond to social challenges, such as simulated territorial intrusions, by rapidly increasing their concentrations of plasma androgens, such as testosterone (T). This increase may facilitate the expression of aggressive behavior and lead to persistence of this behavior even after withdrawal of the challenge, thus potentially promoting territoriality and the probability of winning future challenges. The scope of the Challenge Hypothesis was tested by exposing free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback (SPB) at the beginning of the vernal nesting season. Exposure to SPB stimulated aggressive behavior but did not influence plasma T. Furthermore, plasma T did not correlate with the duration of exposure to SPB, and the behavioral response to SPB did not differ in males that were challenged a second time shortly after the first challenge. As birds were investigated at a stage of their reproductive cycle when plasma T is presumably seasonally high due to photostimulation, the lack of hormonal response to SPB may have been due to the hypothalamus–pituitary–gonadal axis secreting hormones at maximum rates. This was not the case, however, because administration of gonadotropin-releasing hormone I rapidly stimulated the secretion of luteinizing hormone (LH) and T, and treatment with ovine LH rapidly stimulated T secretion.

Characterization of synaptically connected nuclei in a potential sensorimotor feedback pathway in the zebra finch song system.

Birdsong is a learned behavior that is controlled by a group of identified nuclei, known collectively as the song system. The cortical nucleus HVC (used as a proper name) is a focal point of many investigations as it is necessary for song production, song learning, and receives selective auditory information. HVC receives input from several sources including the cortical area MMAN (medial magnocellular nucleus of the nidopallium). The MMAN to HVC connection is particularly interesting as it provides potential sensorimotor feedback to HVC. To begin to understand the role of this connection, we investigated the physiological relation between MMAN and HVC activity with simultaneous multiunit extracellular recordings from these two nuclei in urethane anesthetized zebra finches. As previously reported, we found similar timing in spontaneous bursts of activity in MMAN and HVC. Like HVC, MMAN responds to auditory playback of the bird's own song (BOS), but had little response to reversed BOS or conspecific song. Stimulation of MMAN resulted in evoked activity in HVC, indicating functional excitation from MMAN to HVC. However, inactivation of MMAN resulted in no consistent change in auditory responses in HVC. Taken together, these results indicate that MMAN provides functional excitatory input to HVC but does not provide significant auditory input to HVC in anesthetized animals. We hypothesize that MMAN may play a role in motor reinforcement or coordination, or may provide modulatory input to the song system about the internal state of the animal as it receives input from the hypothalamus.

RNA Interference of Gonadotropin-Inhibitory Hormone Gene Induces Arousal in Songbirds

Gonadotropin-inhibitory hormone (GnIH) was originally identified in quail as a hypothalamic neuropeptide inhibitor of pituitary gonadotropin synthesis and release. However, GnIH neuronal fibers do not only terminate in the median eminence to control anterior pituitary function but also extend widely in the brain, suggesting it has multiple roles in the regulation of behavior. To identify the role of GnIH neurons in the regulation of behavior, we investigated the effect of RNA interference (RNAi) of the GnIH gene on the behavior of white-crowned sparrows, a highly social songbird species. Administration of small interfering RNA against GnIH precursor mRNA into the third ventricle of male and female birds reduced resting time, spontaneous production of complex vocalizations, and stimulated brief agonistic vocalizations. GnIH RNAi further enhanced song production of short duration in male birds when they were challenged by playbacks of novel male songs. These behaviors resembled those of breeding birds during territorial defense. The overall results suggest that GnIH gene silencing induces arousal. In addition, the activities of male and female birds were negatively correlated with GnIH mRNA expression in the paraventricular nucleus. Density of GnIH neuronal fibers in the ventral tegmental area was decreased by GnIH RNAi treatment in female birds, and the number of gonadotropin-releasing hormone neurons that received close appositions of GnIH neuronal fiber terminals was negatively correlated with the activity of male birds. In summary, GnIH may decrease arousal level resulting in the inhibition of specific motivated behavior such as in reproductive contexts.

A possible phylogenetically conserved urgency response of great tits (Parus major) towards allopatric mobbing calls

Black-capped chickadees Poecile atricapillus alter the number of D notes of their chick-a-dee call to reflect urgency and threat. Here, I tested whether heterospecific responses of an allopatric species to these mobbing calls occur. Heterospecific chickadee mobbing calls and songs from North America were broadcast to European great tits (Parus major) and compared with conspecific mobbing calls. During conspecific mobbing playbacks, all great tits approached the speaker, during the heterospecific “chick-a-dee” playbacks, 63.3% individuals approached the speaker, while during the song playback, only 31.3% of the great tits approached the speaker. Minimum distances of great tits were lower during conspecific mobbing calls compared to allopatric chick-a-dee calls and to allopatric chickadee song. Also, minimum distances were lower when comparing allopatric chick-a-dee calls and chickadee song. Great tits approached the speaker on average down to (mean ± SE) 20.0 ± 1.8 m during playbacks of 1–4 D elements, to 17.7 ± 2.0 m during playbacks of 5–7 D elements and down to 11.5 ± 2.0 m during playbacks of 8–11 D elements. The number of D notes was inversely related to minimum distance. Thus, the urgency message encoded in the D notes was perceived also by an allopatric but phylogenetically related European species, suggesting that the heterospecific response is possibly phylogenetically conserved.

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.

Territorial song sparrows tolerate juveniles during the early song-learning phase

Avian song learning is an important model system for understanding vocal learning in humans and other animals. Laboratory studies indicate that social interactions are critical for song learning, but field observations show that territorial males are aggressive to intruders, raising the question of whether young birds are tolerated, much less tutored in the wild. We examined how adult song sparrows (Melospiza melodia) treat juvenile and adult intruders during different seasons important for song learning—summer, autumn, and spring—using taxidermic mounts and song playback. Territorial adults responded aggressively to adult intruders throughout the year. Adults were tolerant of juvenile intruders in the summer, displayed somewhat reduced aggression in the autumn, but treated juveniles like adult intruders by the spring. In the summer and autumn trials, wild juveniles approached our simulated ‘‘interactions’’ between subjects and adult mounts; these wild juveniles were also tolerated, even at close distances. That juveniles can and do closely approach adults during the early sensitive phase of song learning suggests that direct interactions with adults are possible and might be important for learning. In contrast, since young birds are treated aggressively in early spring, most late song learning likely happens through eavesdropping or long-distance singing interactions.

Selective encoding of conspecific signals in a noisy habitat

Event Abstract Back to Event Selective encoding of conspecific signals in a noisy habitat Manfred Hartbauer1*, Marian E. Siegert1 and Heiner Römer1 1 Karl-Franzens University Graz, Zoology, Austria In a habitat with multiple sound-producing species, such like the nocturnal tropical rainforest, conspecific signals sometimes overlap in the time and frequency domain with heterospecific signals, which challenges the detection of relevant signals and their discrimination from irrelevant noise by receivers. We studied this problem in two tropical katydid species of the genus Mecopoda where males of one species produce chirps in regular intervals of 2 s (species “S” named after Sismondo 1990), whereas the other produces long-lasting continuous trills with a rather similar frequency spectrum (3-95 kHz). We investigated the neuronal basis of detecting conspecific signals in the chirping species during simultaneous playbacks of either natural nocturnal habitat noise or varying levels of the calling song of the trilling species. We monitored the activity of TN-1, an afferent auditory interneuron known for its reliable chirp responses from previous studies [1]. Conspecific chirps are reliably represented as bursts of AP´s in this neuron even at a signal-to-noise-ratio of 0 dB (background noise or the trilling song broadcast at the same amplitude as the chirp, 65 dB SPL). Although TN-1 responses gradually declined with increasing levels of the song of the trilling species, TN-1 still discharged with 2 APs/chirp at a S/N ratio of -5 dB. Interestingly, rainforest background noise or the song of the trilling species alone hardly ever elicited a response, except after stimulus onset. Modifying either the frequency content of the chirp or the species-specific temporal pattern in the amplitude modulation of the syllable sequence within the chirp resulted in a reduced TN-1 response during simultaneous playback of the trilling song. Therefore, the selective response of TN-1 to conspecific signals appears to depend on differences in temporal structure and frequency content of conspecific signals and natural maskers. Acknowledgements Research was funded by the Austrian Science Fund (FWF): P21808-B09.

Song patterning, output, and function in the grasshopper sparrow.

Event Abstract Back to Event Song patterning, output, and function in the grasshopper sparrow. Bernard Lohr1* 1 University of Maryland Baltimore County, Department of Biological Sciences, United States Grasshopper sparrows (Ammodramus savannarum) produce two distinct classes of song. The type I song, also known as the “buzz song,” is the principal advertisement song. This species also produces a secondary or type II song class, the “warble song.” Each male grasshopper sparrow sings a single buzz song and a single warble song. Warble song is less commonly produced than the buzz song. Typically, males produce buzz song immediately upon arrival on the breeding grounds in late April, and it can be heard throughout the summer until early August. Within a week to 10 days, if paired, males often begin appending warble song to the end of the buzz song, producing a double song. By the latter part of each month-long breeding cycle, males may switch to singing the warble song by itself. Figure 1 shows spectrograms of the buzz and warble songs of two individuals. I measured the patterning of buzz and warble song production, as well as total song output, using long-term autonomous recording units in male grasshopper sparrow territories at the Chester River Field Research Center during the summer of 2011. Eight of these recording units, operating from 05:00–11:00 EDT (6 hours/day), were deployed in the approximate center of grasshopper sparrow territories. An additional four units were operated in the same habitat from 05:00–23:00 EDT (18 hours/day). We found an expected singing peak from 05:00–08:00, a long period of relatively little singing from 08:00–20:00, and a smaller, though substantial singing peak around 20:30 (sunset). Slightly over 50% of each day’s song was produced in the first 6 hours of the day. Male singing patterns during the course of a breeding cycle were less stereotyped than originally thought, but showed a consistent increase in the proportion of warble song after egg-laying by the female, and a consistent increase in the proportion of buzz song following fledging and the initiation of a new breeding cycle. To investigate potential functions of the two song classes I used a song playback experiment with targeted males known to be singing either the buzz song, or double/warble song. Males singing the buzz song responded to playbacks of both buzz and warble song exclusively with buzz song. Responses by males singing double or warble song were mixed, but these males responded to playbacks of both song classes with buzz song at greater levels than chance. These results suggest that the buzz song is the principal class of song used in interactions between territorial males. The function of the warble song class remains unclear. It may have predominantly intersexual functions such as social cohesion or reproductive synchrony within the pair. Another intriguing possibility is that extra-pair matings may be a consequence of female choice based on the warble song rather than buzz song. Future tests will look for possible associations between the timing of extra-pair mating and the song class being sung by extra-pair mates. Figure 1 Acknowledgements This work was funded, in part, by the Chester River Field Research Center, and the UMBC Department of Biological Sciences. Keywords: birdsong, grasshopper sparrow, Sexual selection, song discrimination, vocalization Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Communication Citation: Lohr B (2012). Song patterning, output, and function in the grasshopper sparrow.. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00386 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 May 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Bernard Lohr, University of Maryland Baltimore County, Department of Biological Sciences, Baltimore, Maryland, 21250, United States, blohr@umbc.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Bernard Lohr Google Bernard Lohr Google Scholar Bernard Lohr PubMed Bernard Lohr Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Arthropod Communities Associated with Habitats Occupied by Breeding Swainson's Warblers

Abstract. The Swainson's Warbler (Limnothlypis swainsonii) is an insectivorous songbird and a species of conservation concern in the southeastern U.S. Because it is specialized for foraging in the litter of the forest floor, it is dependent on a well-developed leaf-litter layer. However, this reliance on the litter layer likely reflects selection of habitats with abundant arthropods for food. To investigate this possibility, we examined relationships between Swainson's Warbler presence and both abundance and diversity of ground-dwelling and litter arthropods. In 2004 and 2005, using song playbacks, we surveyed 1453 sites and collected arthropods in litter samples and pitfall traps at 45 randomly selected occupied and unoccupied sites. In litter samples, total mean arthropod abundance, abundance of arthropods ≥5 mm in length, total abundance of adults, and taxonomic richness were significantly greater at sites occupied by Swainson's Warblers than at unoccupied sites. In pitfall data, however, we detected n...

Responses to Variation in Song Length by Male White‐Crowned Sparrows

AbstractBird song has the potential to convey a variety of information about the singer, including the singer’s current motivational state. A recent review by Searcy & Beecher (2009) (Anim. Behav. 78, 2009; 1281) emphasized how little is currently known about whether song functions as an aggressive signal in territorial interactions. A recent observational study of song length variation in the Puget Sound white‐crowned sparrow reported that males shorten the terminal trill in their single song type while singing close by another male, and shorten the trill even further immediately before chasing the opponent. Here, we report the results of two song playback experiments designed to test whether males distinguish the differences in song length that occur in agonistic and non‐agonistic contexts. We found that males gave stronger responses, as measured by close approach distances, to either a series of songs increasing in duration (compared to a series decreasing in duration), or to long loud songs (compared to short soft songs). In both experiments, males gave weaker responses to the stimuli hypothesized to be more aggressive. Males shortened their songs in response to both simulated intrusions. Combined with the observational data on song variation in different contexts, these experiments support the conclusion that song length variation contains information about aggressive motivation in the white‐crowned sparrow.

Song duets function primarily as cooperative displays in pairs of happy wrens

Vocal duetting occurs in diverse animal groups. Members of a mated pair may duet to communicate with each other or with other individuals. Many hypotheses have been proposed to explain the function of duets, and studies often provide support for the joint resource defence or mate-guarding hypotheses. We evaluated these hypotheses for the happy wren, Pheugopedius felix , using a two-speaker playback experiment. We observed the responses of happy wren pairs to playback of solo male, solo female and male/female duet songs, and compared these with heterospecific song control trials. Happy wrens responded aggressively to conspecific song playback by moving closer to their mate, approaching the playback speakers and increasing singing rates. Both sexes increased singing and especially duetting rates in response to conspecific playback. There were no differences in which sex initiated or terminated duets nor did birds vary the proportion of their partner’s songs answered across conspecific treatments. Furthermore, neither sex treated unmated intruders (solo playback) as more threatening than mated intruders (duet playback). Together, these results argue against the mate-guarding hypothesis and instead indicate that duetting in happy wrens functions primarily in cooperative territory defence. Overall, males sang more than females, moved closer to the speakers and were more likely to answer their partner’s songs, suggesting that males take a primary role in territorial defence. However, females also responded strongly, especially when female intruders were present (duet or female solo playback), which suggests a sex-specific division of labour in their territorial defence.

Expression and rapid experience-dependent regulation of type-A GABAergic receptors in the songbird auditory forebrain

GABAergic transmission influences sensory processing and experience-dependent plasticity in the adult brain. Little is known about the functional organization of inhibitory circuits in the auditory forebrain of songbirds, a robust model extensively used in the study of central auditory processing of behaviorally relevant communication signals. In particular, no information is currently available on the expression and organization of GABAA receptor-expressing neurons. Here, we studied the distribution and regulation of GABAA receptors in the songbird auditory forebrain, with a specific focus on α5, a subunit implicated in tonic inhibition and sensory learning. We obtained a zebra finch cDNA that encodes the α5-subunit (GABRA5) and carried out a detailed analysis of its expression via in situ hybridization. GABRA5 was highly expressed in the caudomedial nidopallium (NCM), caudomedial mesopallium, and field L2. Using double fluorescence in situ hybridization, we demonstrate that a large fraction of GABRA5-expressing neurons is engaged by auditory experience, as revealed by the song-induced expression of the activity-dependent gene zenk. Remarkably, we also found that α5 expression is rapidly regulated by sensory stimulation: 30 min of conspecific song playbacks significantly increase the number of GABRA5-expressing neurons in NCM, but not in other auditory areas. This effect is selective for α5, but not γ2 transcripts. Our results suggest that α5-containing GABAA receptors likely play a key role in central auditory processing and may contribute to the experience-dependent plasticity underlying auditory learning.

Birdsong learning in the laboratory, with especial reference to the song of the Zebra Finch (Taeniopygia guttata)

Vocal imitation in songbirds exhibits interesting parallels to infant speech development and is currently the model system of choice for exploring the behavioural, molecular and electrophysiological substrates of vocal learning. Among songbirds, the Zebra Finch (Taeniopygia guttata) is currently used as the ‘flying mouse’ of birdsong research. Only males sing and they develop their song primarily during a short sensitive period in early life. They learn their speciesspecific song patterns by memorizing and imitating the songs of conspecifics, mainly adults. Since Immelmann's pioneering work, thousands of zebra finches have been raised in strictly controlled auditory environments to examine how their experience affected their songs. In this article, I review the different experimental procedures that have been used in the laboratory to study the social influences on song learning in the Zebra Finch. Poor song learning was observed using passive playback of taped songs, whereas self-eliciting exposure using operant tutoring techniques induced significant learning, but with a high interindividual variability. The success of the training paradigm is often measured by the quality of imitation of the songs to which the young bird is exposed. Using empirical evidence from the field and the laboratory, I will also discuss this issue, by summarizing possible advantages and disadvantages of producing a perfect imitation. So far, the best method to get a close copy of a song model in the Zebra Finch is to place a single young bird with an adult male. This situation, which is rather unnatural, does not meet the criteria for precise control necessary in experimental conditions. Optimizing the methods used to train a zebra finch to learn a song, in order to be able to predict the imitation success, will improve our understanding of the dynamics of vocal production learning. It would also consolidate this species as a research model of relevance to human speech development and disorders. Keywords: Zebra Finch; birdsong; learning; development; memory; social influences