The negative impact of ichthyophagous birds on fish stocks are now matter of great concern. The aim of this study is to assess the wintering diet of the Great Cormorant (Phalacrocorax carbo sinensis) in the S. Antioco lagoon (south-western Sardinia). Through the morphological analysis of undigested hard body parts, such as otoliths, it was possible to trace to the preyed species, their size, biomass and, then, to the average daily consumption of cormorants.