Many migratory species accumulate large amounts of energy reserves prior to migratory flights, of which most is fat, to fuel their migratory flights across inhospitable areas such as sea and deserts with no feeding opportunities. In many species fueling happens immediately before crossing ecological barriers or shortly after the obstacle to replenish used body reserves and to prepare for the continuation of migration and subsequent breeding during vernal migration. Thus, intact stopover sites are crucial for successful migration and overall fitness, respectively. Climate induced changes on habitats will have impacts on staging, stopover ecology and fueling in migratory birds, though the effects of these changes are still very speculative due to the lack of detailed studies and the uncertainty in climate models. Results/Conclusions
The paper will summarize the current knowledge, and it will in particular show that geographical variation in climate induced changes on habitats affect migratory birds due to an increasing mis-match of formerly synchronized migratory events along the flyways. In addition, due large-scale geographical variation of climate change, for example of North Atlantic Oscillation, migratory flyways are differentially affected.
Moreover, there is recent evidence for climate induced changes in trophic relationships which impact fueling. This could either be a mis-match between the temporal pattern of fueling and the availability of food, or climate-induced changes of the nutritional quality of prey. On the other hand, there is evidence that migratory birds are able to counteract adverse condition by showing plasticity in their migratory performance. However, the more the species rely on endogenous timing of migration, the less flexible they might be, and the less prone they might be for evolutionary changes. Consequently, over a long run, species-composition of bird assemblages may change, though we should always keep in mind that climate-induced changes are just another factor on top of the many other human impacts on biodiversity, in particular loss of habitats and food resources due to human activities.