White storks, copyright Eyal Bartov
Migrating Birds Face Many Threats
Over recent years, migrant birds traveling between Africa and the Palearctic have shown a sustained, often severe, decline in populations. Some species, such as the Pallid Harrier (Circus macrourus) and the Lesser Kestrel (Falco naumanni) are disappearing from regular breeding sites. The diminishing numbers may reflect climate change and widespread environmental damage, such as drought and desertification, and massive pesticide use on African farmland.
Pollution, pesticide use, drought, and changes in land use, especially wetland drainage in Africa, have led to a marked decline in the world population of white storks. About 400,000 of them pass through East Africa on their way from central Europe and western Asia, following the Great Rift Valley into southern Africa.
Protecting migratory birds is challenging, because it involves safeguarding the wide range of habitats they require during their seasonal cycle, including breeding areas, wintering grounds, and stopover sites for resting and feeding. A "flyway approach" to conservation takes a holistic view towards protecting the entire migration route, embracing an array of different ecosystems across many countries and political borders.
Climate change is affecting many migrating birds, particularly long distance migrants whose migration rhythms tend to be more fixed or species with very small ranges where they occur in a very specific habitat. Human-induced global warming is occurring so fast that many species are not able to keep up with the necessary adaptations. Other threats add additional stresses for migrating birds, including pollution, hunting, land degradation and development, habitat loss and competition from invasive alien species.
Climate change in the form of extreme weather, changing temperatures, increasing storms, flooding, and rising sea levels all contribute to loss of these habitats or cause the habitats to change. Desertification is another threat. Climate change decreases rainfall in the Sahel, causing the Sahara Desert to grow. African-Eurasian migrants that must cross the Sahara have an increasingly arduous journey, and a greater distance without rest.
Climate change is causing many migratory birds to either abbreviate or cancel their journeys, with severe consequences. Resident birds benefit from milder winters and this increases competition between the migrant and resident species for food and breeding grounds. In some regions, migrants are arriving earlier in their breeding grounds, and nesting earlier, encouraged by the warm spring temperatures. While the vegetation blooms and insect hatchings are also occurring earlier, they are no longer synchronized with the migrations, causing a shortage of food for the new offspring.
Climate change is already affecting birds in diverse ways: BirdLife State of the World's Birds website. Available from BirdLife International.