Importance of climate change for the ranges, communities and conservation of birds

In this review, we focus on the effects of global climate change on the size and position of geographic ranges and the richness and composition of bird communities. Plenty of evidence exists demonstrating that range boundaries of birds are correlated with climatic factors. In general, the northern range limit of species seems to be influenced rather by abiotic factors such as cold temperatures. The southern range limit of species appears to be determined by climatic factors such as heat or lack of water in and regions and by biotic factors in more humid regions. For communities, species richness is best predicted by measures of ambient temperature at high latitudes and by water-related variables in low-latitude, high-temperature regions. Models predicting range changes under climate change show idiosyncratic responses of different species with range contractions being more frequent than range expansions. Range shifts have been observed in temperate regions with northward shifts of northern range boundaries and no consistent trend of southern range boundaries. Further, upslope movements have been observed on a tropical mountain. For communities, increases in species richness are predicted for northern latitude and high-elevation sites and declines of species richness in and regions. With increasing winter temperature, declines in the proportion of migratory species in bird communities have been predicted and observed. Conservation consequences of global climate change are especially high threats to species in and environments, expected movements of species out of protected areas and increasing land use conflicts. In general, surprisingly few studies document effects of climate change on birds' ranges and communities. Given that range contractions and declines of species richness often initiate conservation efforts, further studies are urgently needed.