Recognition of Eggs and Young By the Carrion Crow (Corvus Corone)

A series of experiments were conducted in order to study the way in which the aggression of the Carrion Crow changes in relation to whether its nest contains eggs or nestlings, and if crows recognize their eggs and young. These experiments were carried in four stages in the breeding cycle, namely: complete nests without eggs, nests with full clutch of eggs, nests with nestlings younger than ten days and nests containing chicks older than three weeks. Eggs and nestlings of crows, rooks, herring gulls and domestic hens were offered in these nests and on the ground near them. It was found that crows did not develop a mechanism for egg recognition and that their mcchanism for chick recognition develops quite late in the breeding season.