Local extinction, colonisation and turnover rates of breeding birds in fragmented landscapes: differences between migratory guilds

Abstract

Several features of habitat fragmentation, including habitat area, isolation from other suitable habitats and habitat-edge phenomena, have been associated with negative effects on animal populations. Most studies on birds have concerned forest islands. In this paper I tested a hypothesis of different sensitivity of birds to fragmentation. In selected heterogeneous habitat fragments in southern Poland I analysed differences in local extinction, colonisation and turnover rates between groups of species of different migration status. Some disparities are expected because of the differences in the mobility of birds, as reflected in species dispersal distances. Only for resident species does the number of species lost between two breeding seasons significantly differ from the number of species gained. No significant differences in turnover rates were evident between the guilds. However, the extinction rate of tropical migrants was higher than that of European migrants and the colonisation rate of resident species was lower than that of tropical migrants. Changes in the breeding species composition were not of the island-mainland type. The variables important for explaining year-to-year changes were: "number of habitats" per fragment, fragment size, perimeter, distance to other fragments, vegetation density, number of connectedness and surrounding features. However, there were differences in the importance of these variables to the migratory guilds. The results indicate that the populations of many species of each of the guilds continue to occupy those fragmented landscapes where their long-term persistence will depend on continued dispersal. However, it is difficult to discern for each group whether the changes are caused by dispersal due to alterations in habitat structure and configuration or by stochastic processes.