Besides excavating for food, what is the main purpose of the behavior known as 'drumming'?

Answer

Territorial declaration or mating call

Woodpeckers peck resonant holes into wood, using the material as an amplifier, primarily to communicate territorial boundaries or attract mates.

Besides excavating for food, what is the main purpose of the behavior known as 'drumming'?
birdanatomyphysical characteristicwoodpeckerbeak