Foraging carpenter ants are a dominant force and vital link in the forest food web.  The impact of carpenter ants on a forest ecosystem is immense.  They play a key role by serving as the premier natural biocontrol agents of such forest defoliators as tent caterpillars and spruce budworms.  However, since most species of carpenter ants are nocturnal, studies of predation are difficult to conduct and are therefore few in number.

Carpenter ants can also be considered an indicator species of the health of a forest.  For example, pileated woodpeckers, Hylatomus pileatus, are rarely or never seen in forests without Camponotus modoc. This carpenter ant selects nest sites in decaying stumps and current monoculture techniques in our large forests do not allow for a variety of habitats such as decaying stumps.  Thus, pileated woodpeckers are not seen in such managed forests.  In the western United States,  the pileated woodpecker, a crow-sized bird, will not survive the winter without access to trees, snags, or tree stumps containing colonies of the carpenter ant since carpenter ants constitute the bulk of the winter diet of these large woodpeckers (Figure 10).

Figure 10. The pileated woodpecker depends upon the presence of carpenter ants as a protein source.  These pileated woodpecker chicks await the arrival of one of their parents.

Figure 11. Many species of passerine or perching birds occasionally “ant,” often after new feather growth.  Here is shown a bluejay (Cyanocitta cristata) engaging in passive anting with carpenter ants. Even poultry, such as the peafowl may engage in anting.  In active anting, the birds place ants in their feathers with their beaks.

On the other hand many species of birds undergo “anting,” a process where ants (including carpenter ants) are used for their excretions in the bird’s act of preening.  The purpose of this behavior is unknown but some scientists speculate that it may serve an anti-ectoparasitic or antibiotic function (Figure 11).