Showing papers by "Vincent Bretagnolle published in 2003"

Species-specific song convergence in a moving hybrid zone between two passerines

Abstract: Moving hybrid zones are receiving increasing attention. However, so far little is known about the proximate mechanisms underlying these movements. Signalling behaviour, by individuals engaged in interspecific sexual and aggressive interactions, may play a crucial role. In this study, we investigated song variation within a moving hybrid zone between two warblers, Hippolais polyglotta and H. icterina. In these species, song is involved in interspecific territoriality and, probably, in mixed pairings. We showed that allopatric populations of the two species are clearly acoustically differentiated. However, interspecific differences faded out in sympatry as a result of an overall pattern of convergence. Unexpectedly, the two species converged for different song parameters, namely temporal parameters for H. icterina and syntax for H. polyglotta. Hybridization and interspecific competition could explain convergence in H. icterina. Instead, in H. polyglotta we suggest that local adaptation to habitat and interspecific learning might contribute to convergence. We particularly stress that cross-species learning, by maintaining high levels of interspecific interactions, may influence the movement of the zone. (C) 2003 The Linnean Society of London. (Less)

Activity patterns, habitat use, foraging behaviour and food selection of the Ouvéa Parakeet (Eunymphicus cornutus uvaeensis)

Abstract: Habitat use, activity pattern, foraging behaviour and habitat selection of the Ouvea Parakeet (Eunymphicus cornutus uvaeensis) were studied from July 1994 to December 1996 on the island of Ouvea (New Caledonia, south-west Pacific), using line transects, quadrats, and radio-telemetry techniques. Home ranges of juveniles were small (mean 2.3 ha), and no dispersal from the natal area was observed up to nine weeks post-fledging. Parents spent 80% of their time during the breeding season within the home range of the juveniles and were seen near the nest site throughout the year. Parakeet densities on two study quadrats were higher (0.31 and 0.42 birds ha–1) than the average density found in a previous transect census (0.22 ± 0.09 birds ha–1). More than 20 plant species were foraged, seven of which represented 70% of the diet (31% for the single Ficus sp.). The phenology of the plants foraged on by the parakeet was marked by a long fruiting season, leading to a relative abundance of food throughout the year, especially during the breeding season. Observations on behaviour (time spent on foraging, absence of inter- or intra-specific competition for food) suggest that food is not a factor limiting the population size of the parakeets. The parakeet's habitat is tall forest, including Melanesian fields, where its distribution is remarkably patchy. The possibility of nest-site limitation is assessed in the context of the conservation of this endangered parakeet.