Bird communities in suburban patches near Paris: Determinants of local richness in a highly fragmented landscape

Abstract

:Local species richness in highly fragmented landscapes is expected to be affected by characteristics of both the considered patch and its surrounding matrix, especially in areas dominated by human activities. However, the proximity of other suitable habitat patches may also be determinant for the conservation of biodiversity by enhancing dispersal and thus, “rescue effects” and re-colonization. We investigated breeding bird communities on 63 patches suitable for wildlife in the suburbs of Paris, France, in 2003. After exploring the spatial structure of the data, we tested hypotheses relating local species richness to patch characteristics (size and vegetation), urbanization intensity around patches, and patch isolation relative to the nearest natural remnant. Spatial dependence in the data was considered in the regression analyses because patch distribution may affect local species richness through ecological processes and non-independence between patches situated nearby can pose statistical problems. Fifty-seven regular breeding bird species were recorded over the entire study area. Local bird species richness, patch size and vegetation descriptors were not spatially autocorrelated. Conversely, urbanization intensity around the patches and patch isolation were spatially autocorrelated. Species richness was mainly related to patch size and to the diversity of trees and shrubs, while neither herbaceous plants nor patch distance to the nearest large forest remnant had significant effects. Moreover, we found that the degree of urbanization around patches did not provide a strong predictor of bird richness, which is more newsworthy. Overall, this study stresses once more the complexity of factors and processes responsible of community patterns in urban landscapes. It also highlights the need to explicitly consider spatial issues when investigating these patterns.