Sparrows are social animals. They live in groups in the whole year: they often breed in colonies and they feed in flocks both in the reproductive season and the rest of the year. When foraging, sparrows use two alternative tactics to get food. First, sparrows may search food for themselves ('producing'). Alternatively, sparrows may exploit the food discovery of their flock members ('scrounging'). These individuals either 'steal' food items from a food patch that is found and occupied by another flock member, or they may use aggression to chase away the owner of the patch and take over the food supply.

Recent researh has shown that the use of these alternative tactics is far from being random: individuals in certain circumstaces tend to use producing whereas in others prefer scrounging. What are the factors that determine the choice between the two alternative tactics? Why those factors? What are the payoffs of the tactics? We investigate these questions in field and lab experiments.