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De nombreuses études portant sur les dialectes ont ouvert de nouvelles perspectives sur l’origine, le maintien et la fonction des dialectes chez les oscines. Trois hypothèses ont été formulées : le modèle historique (les dialectes résulteraient d’effets secondaires de l’apprentissage vocal), le modèle de spécialisation raciale (les dialectes résulteraient de populations génétiquement distinctes) et le modèle d’adaptation sociale (les dialectes résulteraient d’apprentissages à fonction sociale). Les caciques cul-jaune (Cacicus cela) ont été un modèle pionnier pour la mise en évidence de dialectes sociaux. Paradoxalement, chez l’espèce voisine des caciques cul-rouge (Cacicus haemorrhous), les dialectes sont indiqués comme étant absents. Le but de cette étude est de vérifier l’existence de dialectes chez les C. cela, de rechercher leur présence chez les C. haemorrrhous, d’étudier leur distribution spatiale et leur stabilité temporelle, et de tester expérimentalement (chez C. cela) leur perception par les membres de la colonie. L’intégralité de l’étude a été réalisée en Guyane Française sur des colonies de nidification. Les paramètres acoustiques temporels et de fréquence des chants courts produits par les mâles de chaque espèce ont été mesurés au cours de plusieurs années. Des expériences ont été menées, où des chants de différents dialectes ont été diffusés dans les colonies. Nous avons trouvé un chant court similaire à celui de C. cela chez C. haemorrhous. Nous avons confirmé la présence de dialectes de colonies proches chez C. cela et démontré leur présence pour la première fois chez C. haemorrhous. Les dialectes des deux espèces présentent une variation temporelle rapide, avec des dialectes différents chaque année au même endroit (différence plus marquée chez les C. cela). Les C. cela discriminent les dialectes de leur propre colonie des dialectes d'origine lointaine. Ils répondent notamment à ces derniers en produisant la première note de leur chant court. Ces résultats favorisent l’hypothèse d’adaptation sociale pour les dialectes chez ces deux espèces de Cacicus. / Numerous studies of dialects opened new perspectives on the origin, sustained presence and function of dialects in oscine birds. Three hypotheses have been proposed: the historical model (dialects would be by-products of vocal learning), the racial specialization model (dialects would be due to genetic differences between populations) and the social adaptation model (dialects would result from socially adaptive learning processes). Yellow-rumped caciques (Cacicus cela) have been a pioneer model for evidencing social dialects. Paradoxically, dialects have been indicated as absent in the closely related species red-rumped caciques (Cacicus haemorrhous). This study aims to verify the existence of dialects in C. cela, seek after the presence of dialects in C. haemorrrhous, study their spatial distribution and temporal stability, and test experimentally (in C. cela) their differential perception by colony members. The whole study was performed in French Guyana at nesting colonies. We measured timing and frequency acoustic parameters of short songs produced by males of both species during several years. We conducted experiments at colonies where we played back songs from different dialects. We found a colonial “short song” similar to that of C. cela in C. haemorrhous. We confirmed the presence of neighboring colony dialects in C. cela and we demonstrated their presence for the first time in C. haemorrhous. Dialects in both species show a fast temporal variation, with different dialects every year at the same place (difference more pronounced in C. cela). C. cela birds discriminate the dialects of their own colony from those of far distant origin. They notably answer the latter by voicing the first note of their short song. These results are in favor of the hypothesis of social adaptation for dialects in these two Cacicus species.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-03-25T01:44:58Z No. of bitstreams: 1 000008CD.pdf: 3707278 bytes, checksum: 479e9bd8617ca8adb079c71f7d8ebe20 (MD5) / Made available in DSpace on 2015-03-25T01:44:58Z (GMT). No. of bitstreams: 1 000008CD.pdf: 3707278 bytes, checksum: 479e9bd8617ca8adb079c71f7d8ebe20 (MD5) Previous issue date: 2013 / UNISINOS - Universidade do Vale do Rio dos Sinos / A biologia de membros da família Icteridae ainda são desconhecidos na América do Sul. O presente estudo apresenta informação sobre a biologia reprodutiva de uma população da espécie ameaçada o Veste-amarela ( Xanthopsar flavus) nos campos de altitude do sul do Brasil. Foram encontrados 18 colônias reprodutivas de 28 ± 25 indivíduos, apresentando uma relação positiva entre o número de pares reprodutivos e o tamanho da colônia (y = .967x + .296; r2 = 0.929, P< 0.001). Foram coletados dados sobre 47 ninhos encontrados durante duas estações reprodutivas de 2011 á 2013 na região fisigráfica dos Campos de Cima da Serra. Reprodução occorre entre os meses de Outubro e Fevereiro e bandos grandes de até 300 indivíduos são encontrados na região esporadicamente entre os meses de Março e Setembro. As fêmeas constroem ninhos de formato de copo aberto de lâminas de grama grossas e finas em vegetação arbustiva aquática (em particular Eryngium horridum, Baccharis trimera e Ludwigia multinervia) á 45,12 ± 24,68 (dp) cm do chão ao longo de três á seis dias (média = 4 ± 1 d, n =6). A postura média é de 3,78 ± 0,55 (sd) ovos, e o s ovos tem uma largura de 2,18 ± 0,08 (dp) cm e altura de 1,62 ± 0,09 (dp) cm. Somenete a fêmea incuba os ovos para um período de 12 ± 1 dias ( n = 5). Fêmeas são mais atenciosas ao cuidado da prole de manhã cedo e no meio da tarde. Machos ajudam alimentar os filhotes mas fazem menos visitas por hora que as fêmeas (U 30 = 74, P= 0,04) e passam até 60% do seu tempo em vigilância. Houve uma relação positiva entre idade do ninhego e número de visitas ao ninho por hora (r 2 = 0.395, P< 0.001). A época de reprodução desta espécie na região dos Campos de Cima da Serra difere em relação às outras regiões na América do Sul, o qual pode estar associado com a disponibilidade de recursos e qualidade do habitat. Em relação á postura e ás características dos ninhos, foram semalhantes aos dados encontrados em Uruguai e na Argentina. Embora seja extirpado na maioridade da sua distribuição original, X. flavus ainda reproduz em grupos relativamente grandes no noroeste do 17 Rio Grande do Sul e esforços de conservação desta espécie deveriam ser intensificados para garantir sua sobrevivência no Brasil. / The life history of many South American icterids is still relatively unknown. We presente detailed information on the breeding biology of a population the vulnerable Saffron-cowled blackbird in the high altitude grasslands of southern Brazil. We found 18 breeding colonies of 28 ± 25 individuals, with a positive relationship between the number of breeding pairs and colony size (y = .967x + .296; r = 0.929, P < 0.001). We collected data on 47 nests found over two breeding seasons from 2011 to 2013 in the Campos de Cima da Serra region. Breeding occurs from mid-October to late January/early February and groups move as large flocks of up to 300 individuals from March to September. Females build an open-cup nest of thick and thin grasses in emergent wetland vegetation or shrubs (mainly Eryngium horridum, Baccharis trimera and Ludwigia multinervia) at 45.12 ± 24.68 (sd) cm above the ground in three to six days (mean = 4 ± 1.26 d, n = 6). Clutch size is 3.78 ± 0.55 (sd) eggs (Range: 3 – 5), and eggs ( n= 19) measure 1.62 ± 0.09 (sd) cm by 2.18 ± 0.08 (sd). Incubation is performed by the female and lasts 12 ± 1days (n = 5). Females are most attentive during the early morning and the mid-afternoon. Males help feed nestlings but make less trips/hr than females (U30 = 74, P = 0.04) and spend up to 60% of their time guarding the nest. There was a positive relationship between nestling age and the number of trips/hr by parents (r 2 = 0.395, P < 0.001). We found discrepancies between the breeding season of X. flavus in the Campos de Cima da Serra region and other parts of Southern South America, which may be related to resource availability and habitat quality. The clutch sizeand nest characteristics were similar to those found for this species in Uruguay and Argentina. Although it has been extirpated from the majority of its original distribution, X. flavus still reproduces in relatively large groups in north eastern Rio Grande do Sul and conservation efforts should be intensified to assure its continued survival in Brazil.