Distribution of breeding, wintering, and resident waterbirds in Europe: biotic regions and the macroclimate

Abstract

We developed a new method of testing whether spatial change in species composition follows a gradual or discrete pattern. To do this, we first divided Europe into regions based on 55 river basins . We then tested similarity of waterbird species assemblages between river basins using presence/absence data, and classified the basins using a probabilistic analysis . Breeding, wintering and resident species were analyzed separately . Some hypotheses related to macroclimate were tested to account for the distribution of waterbird species composition of river basins, using stepwise logistic regression and canonical variate analysis . We detected a strong biotic boundary dividing Europe into large northern and southern regions in both the breeding and wintering seasons. These large regions were subsequently divided, mainly by longitudinal weak boundaries, into a total of six biotic regions for each season. A more fragmented pattern was detected for resident species: four large regions and a total of eight biotic regions. Variables related to temperature characterized the majority of biotic boundaries . Low energy availability of the northern basins in the wintering season may limit the distribution of many wintering species, whereas the higher energy level of the southern basins in the breeding season might cause thermoregulatory stress for many breeding species.