Statistical and Prosodic Cues for Song Segmentation Learning by Bengalese Finches (Lonchura striata var. domestica)

Juvenile songbirds learn their songs from adults. Birds do not simply learn songs verbatim but they sometimes learn parts of songs from multiple tutors and recombine these into one song sequence. How they segment a particular part and select that as a chunk and how these chunks are recombined are interesting questions to ask, because such segmentation and chunking is also considered to be a basic mechanism in human language acquisition. The song of the Bengalese finch has a complex syntax with variable note‐to‐note transition probabilities and could thus be suitable for the study of segmentation and chunking in birdsong. Thirty‐two male Bengalese finch chicks were reared in a large aviary where 11 adult tutors and 10 adult females were breeding freely. In this environment most male chicks learned songs from several tutors. The song note‐chunks that juveniles copied had higher transition probabilities and shorter silent intervals than did the boundaries of the chunks, suggesting that Bengalese finches segment songs using both statistical and prosodic cues. Thus, the Bengalese finch could prove to be an excellent model in which to study neural and behavioral mechanism for sound segmentation.     

Role of a telencephalic nucleus in the delayed song learning of socially isolated zebra finches

Male zebra finches normally learn their song from adult models during a restricted period of juvenile development. If song models are not available then, juveniles develop an isolate song which can be modified in adulthood. In this report we investigate the features of juvenile experience that underly the timing of song learning. Juvenile males raised in soundproof chambers or in visual isolation from conspecifics developed stable isolate song. However, whereas visual isolate song notes were similar to those of colony-reared males, soundproof chamber isolates included many phonologically abnormal notes in their songs. Despite having stable isolate songs, both groups copied new notes from tutors presented to them in adulthood (2.7 notes per bird for soundproof chamber isolates, 4.4 notes per bird for visual isolates). Old notes were often modified or eliminated. We infer that social interactions with live tutors are normally important for closing the sensitive period for song learning. Lesions of a forebrain nucleus (IMAN) had previously been shown to disrupt juvenile song learning, but not maintenance of adult song for up to 5 weeks after surgery. In this study, colony-reared adult males given bilateral lesions of IMAN retained all their song notes for up to 4–7.5 months after lesioning. However, similar lesions blocked all song note acquisition in adulthood by both visual and soundproof chamber isolates. Other work has shown that intact hearing is necessary for the maintenance of adult zebra finch song. We infer that auditory pathways used for song maintenance and acquisition differ: IMAN is necessary for auditorily guided song acquisition—whether by juveniles or adults—but not for adult auditorily guided song maintenance. © 1993 John Wiley & Sons, Inc.     

Song development in the white-crowned sparrow: social factors and sex differences

Results of earlier studies indicated that hand-raised white-crowned sparrows exposed to taperecorded songs learned conspecific song between ages 10–50 days, but not before or after that age. These studies also indicated that allospecific songs were not learned. We describe song development in 41 male and 22 female hand-raised white-crowned sparrows. Thirty males and 15 females were exposed to a live adult singing male. It was found that most male students learned the song of their live tutor even though tutoring was begun at 50 days of age, an age by which young would have dispersed from the natal to the breeding area. Male students learned allospecific song as easily as they did conspecific song, even though conspecific song was present in the laboratory. Only three females copied any part of the song of either conspecific or allospecific live tutors. Six 50-day-old males and seven females were exposed to taperecorded song and none learned the tutor song. These results indicate that there are sex differences in song learning, and that, if live tutors are used, the sensitive phase for male song learning extends beyond 50 days of age. We conclude that social interaction can override any auditory gating mechanism that prevents inappropriate stimuli from influencing song learning centres.     

Social influences during song development in the song sparrow: a laboratory experiment simulating field conditions

Oscine songbirds are exposed to many more songs than they keep for their final song repertoire and little is known about how a bird selects the particular song(s) to sing as an adult. We simulated in the laboratory the key variables of the natural song learning environment and examined the song selection process in nine hand-reared male song sparrows, Melospiza melodia, a species in which males sing 5-11 song types. During their second and third months (their presumed sensitive period), subjects were rotated equally among four live adult male tutors that had been neighbours in the field. Tutors were housed in individual aviary 'territories' in four corners of the roof of a building; subjects could see only one tutor at a time, but they could hear the others at a short distance. Later in their first year (months 5-12), half the subjects were again rotated among all four tutors and the other half were randomly stationed next to just one tutor. Results from this experiment confirm and extend the findings from our two previous field studies of song learning in this species. Young males in this experiment (1) learned whole song types, (2) learned songs from multiple tutors, (3) preferentially learned songs that were shared among their tutors, (4) learned songs that other young males in their group also chose, and (5) learned more songs from the tutor they were stationed next to during the later stage (stationary subjects). These last two results support the late influence hypothesis that interactions after a bird's sensitive period affect song repertoire development. Copyright 2000 The Association for the Study of Animal Behaviour.     

Song learning in domesticated canaries in a restricted acoustic environment

Many songbirds learn their songs early in life from a song model. In the absence of such a model, they develop an improvised song that often lacks the species-typical song structure. Open-ended learners, such as the domesticated canary, are able to modify their songs in adulthood, although the mechanisms that guide and time the song-learning process are still not fully understood. In a previous study, we showed that male domesticated canaries lacking an adult song model in their first year substantially change their song repertoire and composition when exposed to normally reared conspecifics in their second year. Here, we investigate song development in descendants of canaries that were raised and kept as a peer group without a song model. Such males represent tutors with abnormal song characteristics. Interestingly, the F₁ generation developed quite normal song structure, and when brought into an environment with normally raised canaries in their second year, they did not modify their songs substantially. These results suggest that contact with an adult song model early in life is crucial for song crystallization, but also that song development is at least partly guided by innate rules. They also question the existing classification of canaries as open-ended learners.     

Delayed vocal ontogeny in songbirds: a laboratory study validates a model for delayed development derived from field studies

Based on field studies, we proposed a model that describes how vocal ontogeny proceeds over a 2-year period in wild brown-headed cowbirds (Molothrus ater). We tested this model in the laboratory by exposing yearling male cowbirds (n?=?7 tutees), trapped at the start of the breeding season in a southern California dialect, to adult tutors with unfamiliar song types from a different dialect. As adults at the start of their second season, the tutees all had enlarged repertoires based almost entirely on tutor song types. Thus, tutees dropped song types in their yearling repertoires that did not match tutor types and added tutor songs that they had heard for the first time as yearlings in captivity. We discuss these findings in the context of a previous captivity study in which tutees also changed their yearling repertoires but generally failed to copy their tutors’ songs. This is the first laboratory study to fully replicate the delayed ontogeny we have described for wild cowbirds, and validates the delayed vocal development model we proposed. This model is important in a more general context, because it explains how song dialects can remain temporally stable despite immigration by young males with non-local songs.     

Song Learning in Bengalese Finches: a Comparison with Zebra Finches

Male Bengalese finches, Lonchura striata var. domestica, learn their song from an adult male conspecific with whom they can interact at 35 to 70 days of age and normally-raised males fail to reproduce song which they have only heard before or after this time. Birds which have been raised by their mother alone and those which have been deprived of a song tutor during the learning phase produce abnormal songs with indistinct elements and little or no phrase structure; this is typical of males which fail to hear adult song during their development. These songs are unstable and are replaced by normal songs, if there is an opportunity to learn from an adult male conspecific. Presumably, this flexibility in the time when young males learn acts as a safeguard to ensure that normal conspecific song is produced. These results bear striking similarity to those on zebra finch song development. Differences between the two species, especially in the learning of call notes by female zebra finches, are discussed.     

Development of Tonal Quality in Birdsong: Further Evidence from Song Sparrows

Song sparrow (Melospiza melodia) songs are composed largely of pure-tone notes. Song sparrows raised in acoustic isolation (i.e. never hearing conspecific songs) tend to produce half of their notes with harmonic overtones, an atypical tonal structure, suggesting that exposure to pure tones is necessary for the development of normal tonal quality. The experiment presented here directly investigated the influence of early exposure to songs with different tonal qualities on subsequent production. Seven young song sparrow males were exposed to 16 normal, pure-tone song sparrow songs and 6 males were exposed to the same 16 song types with added harmonic overtones. Birds in both groups learned equally well, confirming an earlier finding that tonal quality does not influence selection of models during the sensitive period for song acquisition. Birds exposed exclusively to harmonic song models, however, produced over 85% of their learned notes in a pure-tone fashion, even though they had never heard pure-tone sounds. Thus, pure tones do not need to be experienced directly by song sparrows, but exposure to some features of species-typical song models appears to facilitate the reproduction of models in a pure-tone fashion.     

Song learning with audiovisual compound stimuli in zebra finches

We investigated the effects of audiovisual compound training on song learning in zebra finches, Taeniopygia guttata. In the first experiment, presentation of a stuffed adult zebra finch male was found to be reinforcing to zebra finch males in an operant task. In a separate experiment, zebra finch males were reared without their father from day 7 after hatching onwards. Between 35 and 76 days, they were placed in isolation and exposed to taped songs of a zebra finch male, according to a random schedule (20 presentations/h). For half of the birds, presentation of the song coincided with presentation of a stuffed zebra finch male. For the remaining birds, each presentation of the song was followed by presentation of a stuffed male. The birds were subsequently isolated until day 142, when their own songs were recorded and analysed. Birds in both groups shared significantly more song elements with their tutor songs than with an unfamiliar song. There was no significant difference in song learning between the groups. These results confirm that zebra finches can learn part of their songs from taped tutor songs. Furthermore, simultaneous presentation of the tutor song and a relevant, salient visual stimulus is not superior to sequential presentation. Copyright 1999 The Association for the Study of Animal Behaviour.     

Song Learning in Zebra Finches Exposed to a Series of Tutors during the Sensitive Phase

Young male zebra finches exposed to a series of adult males during their sensitive phase for song learning tended to learn from several of them, in contrast to those exposed to two or more tutors simultaneously. There is a tendency to learn more from later tutors, either because the memory of their elements over-writes that of earlier ones or because sensitivity is greater at this stage. No clear relation could be found between features of the song or behaviour of tutors and whether or not they were copied. In common with earlier studies, tutor song output, beyond a certain minimum was found to be unimportant.     

Effects of location in territory and distance from neighbours on the use of song repertoires by Carolina wrens

By capturing territorial Carolina wrens (Thryothorus ludovicianus) and housing them in portable cages on their territories, I could control each one's location in its territory and distance from neighbours in experiments on the use of song repertoires. Experiment 1 demonstrated that these wrens sang more songs in the centre of their territories than at the edge, but that they did not use more song types or different song types at the centre than at the edge. In experiment 2, in which I played tape-recorded songs at two distances from wrens caged in the centres of their territories, birds responded more strongly to songs at 25m, simulating an intruder, than to songs at 165 m, simulating a territorial neighbour. Birds also switched more frequently between song types and sang more song types per 100 songs in response to the nearer playback. Experiment 3 compared captive wrens 140 m, 80 m, 20 m, or 0 m apart on adjacent territories. As the distance between neighbours decreased, birds sang less, but also switched more frequently between song types, used more song types per 100 songs, and matched songs with neighbours more frequently. There were no differences in the kinds of song types sung at different distances from neighbours. A comparison of the results from experiments 1 and 3 confirms that the use of song repertoires is influenced by distance from conspecifics and not by location in the territory.     

Hatching late in the season requires flexibility in the timing of song learning

Most songbirds learn their songs from adult tutors, who can be their father or other male conspecifics. However, the variables that control song learning in a natural social context are largely unknown. We investigated whether the time of hatching of male domesticated canaries has an impact on their song development and on the neuroendocrine parameters of the song control system. Average age difference between early- and late-hatched males was 50 days with a maximum of 90 days. Song activity of adult tutor males decreased significantly during the breeding season. While early-hatched males were exposed to tutor songs for on average the first 99 days, late-hatched peers heard adult song only during the first 48 days of life. Remarkably, although hatching late in the season negatively affected body condition, no differences between both groups of males were found in song characteristics either in autumn or in the following spring. Similarly, hatching date had no effect on song nucleus size and circulating testosterone levels. Our data suggest that late-hatched males must have undergone accelerated song development. Furthermore, the limited tutor song exposure did not affect adult song organization and song performance.     

Song learning in montane white-crowned sparrows: from whom and when

White-crowned sparrow, Zonotrichia leucophrys, adults and nestlings were colour-banded and songs of mature progeny recorded to determine whether songs were learned from fathers, age peers or adults other than fathers. Four out of 17 sons and daughters sang the same song types as their fathers, indicating that transmission of song from fathers to their young (vertical transmission) is not the norm. Since juveniles do not sing full (‘crystallized’) songs until they are older, transmission from juvenile to juvenile (horizontal) is unlikely on the breeding grounds but may occur if siblings migrate together and hear each other's song on the wintering grounds. The usual mode of transmission is via other adults (oblique). Birds learn one or two songs prior to or during migration, and upon settling on the breeding area the following year may utter only one theme, that which matches the neighbours' songs during matched countersinging bouts. A bird's song dialect is thus not necessarily an indicator of its birthplace. One wild and one laboratory-reared bird sang songs of a Lincoln sparrow, Melospiza lincolnii, and a strawberry finch, Amandava amandava, respectively. These data and data from field playback studies lend support to the notion that interspecific terrioriality may lead to acquisition of alien song for use in matched countersinging during territorial encounters with allospecific neighbours.     

What exactly is ‘local song’ in a population of ortolan buntings with a common dialect?

Previous studies have shown that ortolan buntings (Emberiza hortulana) exhibit apparent dialect variation. Neighbouring males typically share the same final phrase of a simple two-part song. Consequently, the final phrase was considered to be the dialect cue important for discriminating between males from a local population and strangers. Recently, it was shown that in an isolated and fragmented population of the ortolan buntings in Norway there was no local dialect in the above-mentioned sense. Norwegian males often had song types with different final phrases in their repertoire, and had larger repertoires and a lower level of song type sharing than in other populations. It was experimentally revealed that only local songs (L) evoked a strong response in Norwegian males, while these birds did not respond strongly to foreign (F) or hybrid songs composed of local and foreign initial and final phrases in any composition (i.e. both FL and LF songs). These results suggest that, in the Norwegian population, the final phrase of the song is not a sufficient cue for local song dialect recognition. This paper is a further study in which we tested the response of the ortolan bunting males to L, F, FL and LF songs in a typical continuous population (in Poland) in which males share the same single final phrase, i.e. have a common dialect. We found that ortolan bunting males in Poland responded with similar strength to L, FL and LF songs. The majority of males did not respond as strongly to playback of only F songs. Our results suggest that a common final phrase for a population should not be treated as the only signal of ‘locality’. Our results show clear asymmetry in response to hybrid songs with non-local phrases in different populations.     

Facultative development of courtship and communication in juvenile male cowbirds (Molothrus ater)

We investigated effects of naturally occurring variation inexperience with adult males on development of song and courtshipcompetence in captive juvenile cowbirds. We studied birds ingroups housed in large outdoor aviaries that allowed birdsto regulate access to social stimulation. In two aviaries, we housed juvenile males and females either with or withoutadult males. Birds remained in these conditions from September1999 through their breeding season. We documented social andvocal development of juvenile males in the two aviaries bymeasuring social assortment and patterns and frequencies of their song interactions. We then brought the juveniles fromthe two aviaries together to compete against each other foraccess to females. In addition, we recorded juveniles' songsfour times over the study and played back their breeding seasonsongs to females in sound-attenuating chambers to measure the effectiveness of songs in eliciting copulatory responses fromthe females. Compared to juvenile males housed with adult males,juvenile males housed without adult males developed atypicalbehavior patterns. They (1) displayed little intrasexual aggressionor near-neighbor associations and (2) exhibited different patternsof courtship and copulation, but (3) were as successful at competing for copulations. Furthermore, they developed stereotypedsongs sooner and developed more potent breeding season songs.These different outcomes could not be traced to one variablebut to a cascade of effects involving diverging patterns ofsong acquisition and social interaction. The patterns of socialskills that emerged indicate considerable plasticity in the mechanisms underlying acquisition of courtship competence.     

Alternative forms of song matching in song sparrows

Song matching, replying to a song with a similar song, occurs in many songbird species. Almost all investigations of song matching have been of type matching, where one bird's reply is unambiguously similar to the other's song (i.e. the same song type). In many populations, however, neighbours do not share song types, and therefore cannot type-match. We hypothesized that a bird lacking a true type match could still song-match a stimulus song with a song from his repertoire that was similar in some way the birds recognized. We tested this hypothesis in song sparrows, Melospiza melodia, in two playback experiments. We played the subject a stranger song that was similar to one or more of his songs, but a type match to none of them. In the first experiment, we used playback songs that began with two buzzes (‘double-buzz’ songs). In the second experiment, we used songs that began with a slow trill that increased in tempo ('speed-up' songs). Birds replied at rates significantly above chance with their own double-buzz, or speed-up song match to the respective types of playback. The results suggest that birds who do not share true song types, can still song-match each other. This broad-sense form of song matching may also occur in populations with low song type sharing. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Is the Tonal Quality of Birdsong Learned? Evidence from Song Sparrows

Song sparrow (Melospiza melodia) songs are composed largely of pure-tonal sounds. This paper investigates the role that learning plays in the development of the tonal structure of song sparrow songs, as well as the role that tonal quality plays in determining the suitability of songs as models for learning. 20 birds were trained with both normal pure-tonal songs and modified songs that included harmonic overtones. The harmonic-modified songs were obtained from birds singing in a helium atmosphere, the result of which is to perturb vocal tract resonances and thus alter a song's tonal quality. Subjects learned equally well from normal and harmonic models. Birds that learned material from harmonic models reproduced some of this material with harmonic overtones, but the majority of notes learned from harmonic models were subsequently reproduced as pure-tonal copies. Thus, the tonal structure of songs does not influence young song sparrows in their selection of song models, but there is a strong tendency to reproduce songs in a pure-tonal fashion, even if learned from harmonic models.     

Interspecific territoriality in the chaffinch and great tit on islands and the mainland of Scotland: Playback and removal experiments

Territories of the chaffinch (Fringilla coelebs) and great tit (Parus major) overlap on the mainland of Scotland but are mutually exclusive on adjacent islands. Birds on the mainland responded only to playbacks of conspecific song. On the island both species responded to conspecific song and non-conspecific song, but not to the song of the willow warbler. On the island, great tits responded significantly more strongly to songs than did the chaffinches. When chaffinches were removed from part of the island woodland, great tits rapidly expanded into the vacated areas. It is suggested that on the island there is a limit to the co-existence of these two species because they forage in a similar manner and that this has resulted in interspecific territoriality, not seen on the richer mainland environment.     

Does leg-ring colour affect song tutor choice in zebra finches?

Young male zebra finches, Taeniopygia guttata, reared by their mothers alone showed no preference between males with red and with light-green colour rings in their choice of song tutor. Behavioural observations showed that the tutee associated more with the adult from which it was subsequently found to have learnt. In a second experiment, birds reared by both parents wearing either light-blue or light-green colour rings and then given a choice of tutors wearing these ring combinations also showed no preference between them. These young males did, however, more often approach the tutor ringed as their parents had been. This may explain why they did not show more interest in the tutor whose song they learnt. The majority of the tutors were used twice, with the ring colour swapped before they were used the second time. There was a strong tendency for the same male to be copied by the two young birds exposed to him. This could not be attributed to a difference in song rate between the two tutors. Further work will be required to discover the basis of that individual's greater attractiveness. Copyright 1999 The Association for the Study of Animal Behaviour.