Abstract : Deciphering the processes by which human activities influence the diversity of ecological systems, at various temporal and spatial scales, is at the foreground of research in conservation biology. The ecological niche appears in that respect as a relevant conceptual interface. My work addresses the implications of the structure and variations of this interface for our interpretation of the consequences of changes in landscapes, habitats and climatic conditions on biotic communities. I examine this issue through the model of European common birds, for which large-scale data bases allow quantifying the niche in a multivariate and multiscale way. My reasoning holds with three main results. First, beyond the multiplicity of niche axes, exploring their relations and structures allow inferences on the processes that drive the segregation of species along environmental gradients. Second, crossing habitat and climatic niches reveal interactions between sources of vulnerability which seem at a first glance to operate at distinct scales. Last, the breadth of the habitat niche is not only a cause, but also a consequence of species' responses to environmental variations. I explore the consequences of these three major results on our understanding of processes that sustain the taxonomic and functional diversity of biotic communities. I suggest that, beyond the traditional view of the niche as a network of nested filters, accounting explicitly for interactions between these filters and their variations would sensibly improve our ability to explain and predict the ecological effects of global changes.