When individuals forage in groups they may acquire information on the quality of feeding sites from observations of the activities of other individuals. During the non-breeding season, black coots (Fulica atra) directed attacks at conspecifics with the main purpose of supplanting them from foraging sites. By supplanting, coots did not increase the amount of food ingested relative to birds feeding undisturbed, but instead reduced the costs associated with obtaining food by spending less time foraging by the more costly method. The rate of food intake of supplanted coots was lower than that of undisturbed birds, probably not only because following the displacement they moved away, but also because immediately after moving the time spent feeding on plants brought to the surface after each dive was shorter, although they dived with the same frequency as undisturbed coots did. This indicates that supplanted coots were displaced to sites of lower quality. Probably, the extent to which supplanting was performed was related to a decline in food quality arising from dry conditions.