The species of food organisms which were widespread in the forest and had high dispersal rates would be preyed upon by all the warblers. Thus,
competition for food is possible. The actual food eaten does indicate that the species have certain foods in common. The slight difference in habitat
preference resulting" from the species' different feeding zones is probably more important. This could permit each species to have its own center
of dispersal to regions occupied by all species. Coexistence in one habitat, then, may be the result of each species being limited by the availability of
a resource in different habitats. Even although the
insects fed upon may be basically of the same type
in the different habitats, it is improbable that the
same individual insects should fly back and forth
between distant woods; consequently, there would
be no chance for competition. The habitat differences and, equivalently, the feeding zone differences, between hlackburnian, black-throated
green, and bay-breasted are sufficiently large that
this explanation of coexistence is quite reasonable.
The myrtle warbler is present in many habitats
in the summer but is never abundant. It has a
very large summer and winter range, feeds from
the tree tops to the forest floor, and by rapid
peering or by hawking. It makes frequent long
flights and defends a large territory. Probably
it can be considered a marginal species which, by
being less specialized and thus more flexible in its
requirements, manages to maintain a constant, low
population (Figure 10)