The diet of nestling Hooded Crows (Corvus cornix) was investigated in Warta Mouth National Park (W Poland) in the breeding season of 2003. We analyzed 82 food samples of which 79% contained snails and bivalves. Hooded Crows prefer Viviparus spp. instead of smaller but more abundant molluscan species present in the studied area. We suspect that under conditions of the lowland flooded river valleys Viviparus spp., as a relatively large and meaty species, can be eaten without the shell and is a more valuable food source than smaller molluscs.