Controlled experiments were undertaken to examine the quality of the cereal aphid Rhopalosiphum padi as a food source for newly hatched grey partridge Perdix perdix chicks. Growth and flight feather development were measured on chicks fed on three different diets: aphid, grasshoppers, and a mix of the two. Growth and development of flight feathers differed according to diet in the following order: mix > grasshoppers > R. padi. A diet consisting solely of grasshoppers provided sufficient nourishment to partridge chicks but a diet consisting solely of aphids provided poor nourishment. Chicks benefitted from eating R. padi as a supplement to grasshoppers. Our results help to explain why some earlier studies reported a positive correlation between chick survival and cereal aphid density, while others did not.