The effects of the environmental and species’ characteristics were analyzed for the richness and distribution of the dabbling and diving waterbirds in a wetland complex with 26 ponds (0.1-88.6 ha) in southeast Spain. These environments are being lost on a global scale through human activity. Morphological, geographical, hydrochemical, vegetative and temporal parameters of the ponds (11 in total), as well as characteristics of the species, were sampled to identify those variables with the capacity to predict the effects provoked by the habitat configuration. The function of the size and the isolation, as variables related to the habitat patchiness, as well as the development of the emergent vegetation of the wetlands were discriminated as forecasters of number of species. The avian abundance had an important role in the capacity of the birds to occupy ponds (sampling hypothesis). The differences in the abundance of species probably favored their orderly loss from the wetland complex at the same rate as the ponds diminished in size (“nested” pattern). The results obtained imply the need for the conservation or restoration of numbers of wetlands, paying special attention to the largest, with peripheral vegetation cover around large, open water bodies in complexes with more than one pond, to preserve the greatest number of species against the loss of wetlands which is occurring worldwide and is a cause of biodiversity decline.