According to full-day observations (scan sampling), Northern Wheatears (Oenanthe oenanthe) stopping over on the island of Helgoland (SE North Sea) during spring and autumn migration spent 51–67 % of the daylight period foraging. Large parts of the day were used for resting or being vigilant, whereas flying, preening and aggressive behaviour were of minor importance. The density of Wheatears did not influence the time devoted to foraging and aggressive behaviour, and the time spent resting/vigilant was not correlated to predation risk (measured as the rate of raptor flying over). Several observations showed that refuelling on the beach, which presented the most favourable feeding conditions and allowed high rates of body mass gain, was metabolically limited. The total time devoted to foraging was independent of day length, and additional food (mealworms) offered in bowls was completely ignored, an indication that reduced foraging effort would not improve net energy gain within the physiological capacity. In contrast, Wheatears responded strongly to additional food supplied in the poorer grassland habitat. Although this strongly suggests that refuelling is limited by the amount of food available and the costs of obtaining it, foraging times were the same as on the beach. In grassland, the behaviour pattern of birds refuelling was probably distorted by a high proportion of transient and exploring individuals. Therefore, knowledge about foraging ecology and the response to additional food improves the value of the foraging time parameter in considerations of refuelling limitations.