Problem-solving performance is correlated with reproductive success in a wild bird population

► We related problem-solving performance and reproductive success in great tits. ► Problem-solving performance was measured using a new string-pulling task. ► Solver pairs had higher nestling survival until fledging than nonsolver pairs. ► Faster solver pairs had higher clutch size, hatching success and fledgling number. ► Natural selection may thus directly act on problem-solving performance in the wild.