UK cuckoos undertake extraordinary migrations to sub-Saharan Africa each autumn. Satellite tracking has revealed the welfare challenges they face on this journey, informing conservation priorities.
Individual cuckoos tracked by satellite reveal the welfare toll of long-distance migration. Birds that fail to accumulate adequate fat reserves before the Sahara crossing face starvation mid-flight over inhospitable terrain. The dry season in the Sahel provides inadequate insect food, causing prolonged negative energy balance. Deforestation in the Congo Basin removes the caterpillar-rich wintering habitat that provides the nutritional recovery needed before northward migration. Birds that arrive on UK breeding grounds in poor condition have reduced reproductive success, compounding population decline.