The Eurasian blackcap is a highly adaptable warbler that has developed a novel wintering strategy in Britain, but this plasticity raises new welfare questions about garden dependency and dietary change.
Wintering blackcaps are dependent on garden supplemental food during cold spells when natural berry crops fail. Severe frost can cause rapid mortality among birds that have foregone the fat reserves needed for an African crossing. Garden feeders represent a novel ecological dependency that, once established, may create welfare vulnerabilities during unusual winters or periods of food source failure.