Flock-dependent exploitation of a limited resource in House Sparrow.

The performances of different social groups can depend on various characteristics, such as familiarity among their members or the presence of individuals with specific traits. However, it has rarely been investigated how groups perform during an encounter with other conspecifics, even if in the natural environment social groups often run into each other and compete for resources. We investigated whether a certain characteristic of the group (i.e., familiarity) could benefit its members when they are confronted with another group. We designed a novel experimental set-up, creating triads of captive house sparrows (Passer domesticus) and examining whether in a situation of competition for limited resources one triad could gain benefits over the other (consume more mealworms, Tenebrio molitor). While we did not find an effect of previous familiarity among triad members on the triads' performances, we discovered a group-based difference in the number of mealworms eaten per capita. Group-mates of the very first individual to eat a mealworm (first feeder) ate more mealworms than those in the opposing triad. First feeder individuals also foraged sooner and more than other birds in a subsequent prey consumption assay. Our results suggest that individual performances were influenced by group membership, even when groups were exploiting the same resource simultaneously.