1. The behaviour of inter-species hybrids between Carduelis carduelis, Chloris chloris and the domestic Canary was studied. 2. All behaviour patterns which occur in both parent species are unchanged in the hybrids. 3. Behaviour patterns whose form or frequency differs in the parent species, occur in an intermediate condition in the hybrids. 4. Behaviour patterns which occur in one parent species only and which are apparently the result of an evolutionary process in which insignificant intention movements have become stereotyped and exaggerated more in that species than in the other, appear in an intermediate condition in the hybrid. 5. The relation between display components and behaviour tendencies are (qualitatively) unchanged in the hybrids.