As for interspecific territoriality, there is no
exclusion of the kind found in intraspecific territoriality, as is clearly shown in Kendeigh's (1947)territory maps. It is very difficult to distinguish
a mild repulsion of other species by territorialism
from a preference for slightly different habitats.
Adequate information does not exist to make the
distinction at present. However, it seems quite
certain that interspecific territoriality is weaker
than intraspecific and, therefore, that the effect of
a large density of one species is greater on that
species than on the others. It is thus probable
that. in the warblers, territoriality helps reduce
competition and acts as a stabilizing factor (as
well as performing the well-known functions of
pair formation and maintenance).