Bird communities of a temperate forest: spatio-temporal partitioning between resident and migratory species

A lot of bird species are declining in number in Europe, and studies of bird community assembly are fundamental to propose efficient conservation actions. Many studies were conducted on the regional variability of the abundance and distribution of bird communities, but few studies considered the local patch variability and intraseason dynamics, which permit one to mechanistically understand the patterns observed across entire seasons. In this study, we considered the intrapatch variability and dynamics of a breeding bird community in the forest patch of Corbière (Brittany, France). We tested whether bird community distribution was related to habitat characteristics, whether distribution patterns depended on life history traits of species and how patterns changed during the breeding season. Over 3 years, we used regular sampling and the point count method to sample the whole bird community within the forest patch. Our results show that several biotic and abiotic variables (distance to forest edge, deciduous tree cover, coppice cover, elevation) controlled individual abundances of bird species as well as indicators of the bird community (abundance, diversity, evenness). Moreover, we found that the abundances of resident birds, short-distance migrants and long-distance migrants were differently related to biotic and abiotic variables, and that these relationships varied during the breeding season. We suggest that the space partitioning may be explained by the temporal dynamics of the bird community. Specifically, the early arrival of resident and short-distance migrant species in the forest patch might enable them to preferentially choose high-quality habitats. The long-distance migrants considered in this study arrived later in the breeding season and might not find the same habitat availability, and they might consequently nest only close to the forest edge, in high sites or in sites with a sparse understorey. Our results show that local studies, taking into account migratory status and species dynamics on an intraseason scale, are important keys to understand distribution patterns of bird communities which are observed during entire breeding seasons.