PARTIAL MIGRATION IN BIRDS - EXPERIMENTAL PROOF OF POLYMORPHISM AS A CONTROLLING SYSTEM

When, from a partially migratory population of blackcaps, migratory-active (a) and -inactive (i) individuals were bred, the a .times. a pairs produced more birds of the type a than the original population and the i .times. i pairs, and the latter more birds of the type i than the original population. Thus, the characters migratory and resident in the blackcap are inherited and polymorphism is now demonstrated as a controlling system for partial migration in birds.