Group Adherence in the Common Tern

Abstract

In a preceding contribution (Austin, 1940; 153) it was postulated that colonies of Common Terns (Sterna hirundo Linnaeus) breeding on Cape Cod, Massachusetts, form a distinct, concrete group of individuals which is self-sustaining and relatively free from association with other groups during the nesting season.The very small interchange of membership between this and other groups never occurs on the breeding grounds, but only during migration or on the wintering grounds.An addi.tionaldecade of field work and study in this area has yielded data which not only further substantiate the concept of the Cape ,Cod group of .terns,but also show some of the reasons for the persistence of this phenomenon.I,t suggests that while kinship is an important causative factor, as in similar associations of other forms, it is su.pple