Fig. 1. Methodological graph showing the degree of success of the three different treatment categories: (A) fraction of time spent foraging, (B) measurement of intake rate (ash-free dry mass M_AFD per second), as an indication of the extent of energy intake, and (C) measurement of intake rate (shell dry mass DM_shell per second) to indicate shell crushing. These box-and-whisker plots give median (horizontal line within box), interquartile range (box), range (bars), and outliers (small filled circles) among all relevant trials. Larger symbols indicate mean values per individual per treatment category.