THE BEHAVIOUR AND BREEDING BIOLOGY OF THE SHETLAND WREN.

The behaviour of T. t. zetlandicus is shown to differ in several respects from that of T. t. troglodytes and, less markedly, from the behaviour of some other insular races. Attention is called to a type of behaviour which it is suggested should be called " transference activity". It is argued that there is a close connection between the availability of food for the nestlings and the character of the pair-bond, and that modifications in the integrative pattern of adaptations are of importance in speciation.