Sedge warblers undertake remarkable long-distance migrations, fattening intensively before crossing the Sahara in a single non-stop flight. Their welfare is shaped by habitat quality, climate change, and the physiological demands of migration.
The welfare demands on sedge warblers during migration are extraordinary. Inadequate pre-migratory fattening - caused by reduced invertebrate abundance from pesticide use or habitat loss - means birds attempt the Saharan crossing with insufficient fuel reserves, resulting in death by exhaustion. Droughts in the Sahel wintering grounds can cause mass mortality, driving dramatic population crashes. Even at breeding sites, agricultural intensification has reduced ditch and scrub habitats, concentrating birds in smaller, lower-quality areas. Cats, corvids, and other predators impose additional losses at all life stages.