In reality, these are birds of the high northern latitudes, breeding in openings of the boreal forest. Nests are constructed in hummocks of sphagnum and sedges, and because the spruce tree is a characteristic boreal tree, a favorite menu item of the Tennessee Warbler is the spruce budworm, which can break out and defoliate forests of spruce.
Some forestry operations in Canada will spray entire forests with insecticide in order to inhibit the spruce budworm, and more recent advances have led to lepidoptera-specific insecticides. Researchers in Canada have sought to understand whether this spraying affects the Tennessee Warbler, and have discovered that the females will alter feeding behavior in sprayed areas, and as a result will spend less time tending to their brood. However, no negative effects were found on the brood survival. Whether the long-term effects of this spraying will reduce populations of Tennessee Warblers remains to be seen, but their population is stable for now.