The American bittern is more often heard than seen. It spends most of its time in dense reedbeds where its mottled brown plumage provides excellent camouflage, making the bird difficult to spot even from close range. When approached, the bird stretches its neck upwards, elongating its markings so that they strongly resemble the background reeds, and it may even sway its body slightly to match the movement of reed-stalks in the breeze. In the breeding season, however, the bittern reveals its presence with loud, booming calls that have earned it the name 'thunder-pumper'.