Plasticity And Structure Of The Blackcap Song Studied In Migratory And Sedentary Population

L’objectif de la thèse a été d’étudier la structure, la fonction et la plasticité au cours du temps du chant d’un oiseau mâle adulte, la fauvette à tête noire Sylvia atricapilla. L’influence de différents comportements migratoires sur les caractéristiques du chant, sur la maintenance des dialectes et sur l’apprentissage a également été étudiée chez deux populations, une migratrice (représentée par 2 groupes à Paris) et une sédentaire (représentée par 3 groupes en Corse). Le chant de cette espèce est constitué de deux parties aux caractéristiques acoustiques bien distinctes, le warble et le whistle. Nos expériences de diffusion montrent que chacune des deux parties peut provoquer une réponse territoriale des mâles. Ce chant en deux parties permet probablement aux fauvettes de transmettre des informations différentes, destinées à différents auditoires, proches et lointains, mâles et femelles. Nos analyses génétiques par microsatellites ne montrent pas de structure génétique des groupes et populations. Néanmoins, nous avons montré l’existence de variations micro-géographiques au niveau de la composition en syllabes et en séquences de syllabes de cette seconde partie du chant. Bien que le renouvellement des individus soit plus important chez les migrateurs que chez les sédentaires, les 2 populations ont un taux de partage de syllabes et de phrases équivalent au sein des groupes. Nous avons cependant observé que les individus migrateurs ont un répertoire de syllabes 2 fois plus grand mais une diversité de phrases partagées 2 fois moins grandes que les sédentaires. Le suivi d’individus sédentaires sur plusieurs années consécutives a permis de montrer que l’espèce faisait preuve d’une plasticité vocale puisqu’on observe un plus grand partage de syllabes et de phrases intra année qu’inter année au sein des groupes. Même si les individus semblent modifier le contenu de leurs chants chaque année, nous n’avons pas réussi à mettre en évidence par des expériences de diffusion en milieu naturel un apprentissage à l’âge adulte de nouvelles syllabes ou de nouvelles phrases.The aim of the thesis was to study the structure, function and plasticity over time of the song of a male adult bird, the blackcap Sylvia atricapilla. The influence of different migratory behaviors on the song characteristics, on the dialect maintenance and on learning has also been studied in two populations, a migratory one (represented by two groups in Paris) and a sedentary one (represented by 3 groups in Corsica). The song of this species consists of two parts with distinct sound characteristics, the warble and the whistle. Our playback experiments show that both parts trigger male territorial response. Such a song in two parts probably allows blackcaps to transmit different information for different audiences, close and distant, males and females. Genetic analyzes with microsatellites show no genetic structure of groups and populations. Nevertheless, we have shown the existence of micro-geographical variations in the composition of syllables and sequences of syllables in the whistle part. Although the turnover of individuals is higher among migrants than among sedentary populations, the two populations have similar syllables and phrases sharing within groups. However, migratory birds, compared to sedentary ones, have a syllable repertoire size twice as large and a repertoire of phrase sharing much smaller. The survey of sedentary individuals over several consecutive years has shown that the species show a vocal plasticity since a greater sharing of syllables and of phrases is observed intra year than between years within groups. Although individuals seem able to modify their songs every year, we didn’t succeed in showing with playback experiments in natural environment that adults males were able to learn new syllables or new phrases

La plasticité et la structure du chant de la fauvette à tête noire étudiées chez des populations migratrices et sédentaires

The aim of the thesis was to study the structure, function and plasticity over time of the song of a male adult bird, the blackcap Sylvia atricapilla. The influence of different migratory behaviors on the song characteristics, on the dialect maintenance and on learning has also been studied in two populations, a migratory one (represented by two groups in Paris) and a sedentary one (represented by 3 groups in Corsica). The song of this species consists of two parts with distinct sound characteristics, the warble and the whistle. Our playback experiments show that both parts trigger male territorial response. Such a song in two parts probably allows blackcaps to transmit different information for different audiences, close and distant, males and females. Genetic analyzes with microsatellites show no genetic structure of groups and populations. Nevertheless, we have shown the existence of micro-geographical variations in the composition of syllables and sequences of syllables in the whistle part. Although the turnover of individuals is higher among migrants than among sedentary populations, the two populations have similar syllables and phrases sharing within groups. However, migratory birds, compared to sedentary ones, have a syllable repertoire size twice as large and a repertoire of phrase sharing much smaller. The survey of sedentary individuals over several consecutive years has shown that the species show a vocal plasticity since a greater sharing of syllables and of phrases is observed intra year than between years within groups. Although individuals seem able to modify their songs every year, we didn’t succeed in showing with playback experiments in natural environment that adults males were able to learn new syllables or new phrases.L’objectif de la thèse a été d’étudier la structure, la fonction et la plasticité au cours du temps du chant d’un oiseau mâle adulte, la fauvette à tête noire Sylvia atricapilla. L’influence de différents comportements migratoires sur les caractéristiques du chant, sur la maintenance des dialectes et sur l’apprentissage a également été étudiée chez deux populations, une migratrice (représentée par 2 groupes à Paris) et une sédentaire (représentée par 3 groupes en Corse). Le chant de cette espèce est constitué de deux parties aux caractéristiques acoustiques bien distinctes, le warble et le whistle. Nos expériences de diffusion montrent que chacune des deux parties peut provoquer une réponse territoriale des mâles. Ce chant en deux parties permet probablement aux fauvettes de transmettre des informations différentes, destinées à différents auditoires, proches et lointains, mâles et femelles. Nos analyses génétiques par microsatellites ne montrent pas de structure génétique des groupes et populations. Néanmoins, nous avons montré l’existence de variations micro-géographiques au niveau de la composition en syllabes et en séquences de syllabes de cette seconde partie du chant. Bien que le renouvellement des individus soit plus important chez les migrateurs que chez les sédentaires, les 2 populations ont un taux de partage de syllabes et de phrases équivalent au sein des groupes. Nous avons cependant observé que les individus migrateurs ont un répertoire de syllabes 2 fois plus grand mais une diversité de phrases partagées 2 fois moins grandes que les sédentaires. Le suivi d’individus sédentaires sur plusieurs années consécutives a permis de montrer que l’espèce faisait preuve d’une plasticité vocale puisqu’on observe un plus grand partage de syllabes et de phrases intra année qu’inter année au sein des groupes. Même si les individus semblent modifier le contenu de leurs chants chaque année, nous n’avons pas réussi à mettre en évidence par des expériences de diffusion en milieu naturel un apprentissage à l’âge adulte de nouvelles syllabes ou de nouvelles phrases

The two parts of the blackcap song: Acoustic analysis and male responses to playbacks.

International audienceBird songs are complex manifold acoustic signals serving two main functions: mate attraction and territorial defense. The way information is encoded in the song often reflects adaptation to proximate and ultimate constraints. Male blackcaps, Sylvia atricapilla, display versatile songs with two parts, a warble and a whistle, whose functions remain unclear. We showed that the two parts of songs differ in terms of intensity, frequency and temporal parameters. They also contain totally different sets of syllables. Furthermore, the warble is versatile whereas the whistle part shows syllable sharing between individuals leaving closeby. Altogether, the results of our analysis suggest that the two parts encode different information potentially directed to different audiences. In order to test the potential function of these two parts, we performed playback experiments by broadcasting entire songs and each part separately. Warble and whistle alone are sufficient to trigger male responses and males sing both parts in responses to all stimuli, showing that both parts of the song are used in male-male competition. It is suggested that the segregation of information in the blackcap song could be related to public versus private communication, used in both intra- and intersexual contexts, rather than directed to male versus female audiences only

Flight phases in the song of skylarks: impact on acoustic parameters and coding strategy.

Skylarks inhabit open fields and perform an aerial song display which serves as a territorial signal. The particularly long and elaborate structure of this song flight raises questions about the impact of physical and energetic constraints acting on a communication signal. Song produced during the three distinct phases of the flight - ascending, level and descending phase could be subject to different constraints, serve different functions and encode different types of information. We compared song parameters during the ascending and the level phases. We found that the structure of the song varied with the phase of the flight. In particular, song had a higher tempo when skylarks were ascending which might be related to higher oxygen and energetic demands. We also explored which phase of the song flight might encode individuality. Earlier studies reported that skylarks reduced their territorial response to established neighbours if the neighbour song was broadcasted from the correct adjacent boundary, but reacted aggressively if the neighbour songs were broadcasted from an incorrect boundary (mimicking a displaced neighbour). Such differential response provides some evidence for individual recognition. Here, we exposed subjects to playback stimuli of neighbour song in which we had replaced either the song produced during the level or the ascending phase by the relevant song of the neighbour from the incorrect border. Singing response was higher towards stimuli in which the 'level phase song' was replaced, indicating that skylarks could be able to recognise their neighbours based on song of this phase. Thus, individuality seems to be primarily coded in the level phase of the flight song

Maternal responses to pup calls in a high-cost lactation species

International audienceBonding between mothers and their young is fundamental to mammalian reproductive behaviour and individual fitness. In social systems where the risk of confusing filial and non-filial offspring is high, mothers should demonstrate early, strong and consistent responses to their kin throughout the period of offspring dependence, irrespective of maternal traits. We tested this hypothesis through playback experiments in the northern elephant seal Mirounga angustirostris , a phocid species that breeds in high-density colonies. We found that mothers recognized their offspring throughout lactation and as early as 1–2 days after parturition. Measures of experience (age) and temperament (aggressivity) did not predict their response strength to filial playback treatments, nor did pup age or sex. Some mothers showed great consistency in behavioural responses throughout the lactation period, while others were less predictable. The strength of a female's response did not influence her pup's weaning weight; however, more consistent females weaned pups of higher mass. This is a rare demonstration of individual recognition among phocid mothers and their offspring, and suggests that consistency in maternal responsiveness may be an important social factor influencing the pup's growth and survival

Measures of response recorded during playback experiments.

<p>Measures of response recorded during playback experiments.</p

Sound spectrogram of a short part of a flight song of a male skylark.

<p>Each syllable is labelled with a number and syllables belonging to the same syllable type have the same number.</p

Factor loadings of the response measures on the first (PC1) and second (PC2) principal component in playback experiment. Variance explained by the PC scores is given in parentheses.

<p>Factor loadings of the response measures on the first (PC1) and second (PC2) principal component in playback experiment. Variance explained by the PC scores is given in parentheses.</p

Skylarks respond more strongly to S2 stimuli.

<p>Mean scores (±SE) of the first and the second principal components for responses to the two stimuli (S1: level phase of flight song from neighbour of the opposite side; S2: ascending phase of flight song from neighbour of the opposite side). * p = 0.024. Variance explained by the scores is given in parentheses. There was no effect of the order of presentation (GLM, F = 0.53 p>0.1).</p