three species of northern American warblers are found to feed in different parts of the same spruce tree. This particular behavior of warblers displays which ecological characteristic?

This particular behavior of warblers displays that;

They cannot share the same niche in the same habitat.

The correct answer would be the Gause's Competitive Exclusion Principle.

Explanation:

The three different species of North American warblers cannot share the same niche in the same habitat. Such behavior is called a Principle of Gause's Competitive Exclusion.

It says that the competitors with the same bearing can not co-exist in the same niche or habitat. If they present in the same habitat there always be a dominant species.

Thus, the correct answer would be the Competitive Exclusion Principle.