The cuckoo is one of the UK's most iconic summer migrants but has declined significantly, with tracking studies revealing challenges at multiple points in the migration cycle.
Cuckoo welfare is affected by conditions at breeding grounds, on migration routes, and in wintering areas in tropical Africa. BTO tracking has revealed that certain routes through Italy and Spain have lower survival rates than routes through Spain and Iberia, possibly linked to hunting. Conditions in the Sahel stopover zone, where rainfall affects insect prey availability, critically affect survival during the crossing of the Sahara. Invertebrate prey including large hairy caterpillars that cuckoos specialize in eating are affected by insect decline on breeding grounds. Climate mismatch between cuckoo arrival and host species breeding is an emerging welfare concern.