Global Distribution, Conservation Status, Population Trends, and Population Threats

In this chapter, we summarize and review the current knowledge about distribution and temporal changes in population size of the European roller, as well as the evidence of threats to the populations, providing the most up-to-date assessment of the species’ conservation status so far. The European roller is distributed discontinuously from Portugal and North Africa to northern China, with the exact geographic limits of the two existing subspecies remaining unclear. It is tentatively estimated that a population of half a million adult individuals persists, primarily breeding in lowland areas with temperate climates that contain natural cavities. During its wintering south of the African tropic, the roller shows a preference for woodlands, bushveld, and grassland vegetation, avoiding open arid areas. The species has undergone a sharp global decline over the past two centuries, becoming extinct in numerous countries in central and northern Europe, and experiencing significant population declines. In some countries, these declines have only been reversed through the installation of nest-boxes. Habitat loss emerges as a general driver of decline in Europe, manifesting through processes of agricultural intensification, urbanization, deforestation, or afforestation, all of which affect the loss of open natural habitats and the availability of cavities. The use of pesticides in areas with intensive agriculture may have contributed to the decline by reducing populations of invertebrate prey. Additionally, the fragmentation and small size of some populations in northern Europe may be compromising their future viability. However, we have noted an alarming lack of information regarding the threats affecting the species during migration and wintering, as well as for populations breeding outside of Europe. The roller has recently been downgraded from globally Vulnerable to Least Concern on the IUCN Red List, although the reasons for this seem insufficiently justified.