The cuckoo has declined dramatically in the UK, with research using satellite tags revealing high mortality during trans-Saharan migration as a primary cause.
Cuckoo welfare during migration is shaped by conditions across multiple continents. Routes crossing the Sahara in degraded condition can cause starvation and death. UK breeding habitat quality affects pre-migratory condition, while food availability — particularly hairy caterpillars — influences departure condition. Protecting insect-rich habitats, woodland edges with bramble, and damp grasslands simultaneously benefits cuckoos and their food supply.