Male Marsh Wrens destroy eggs of conspecifics in other territories and have been seen to attack their own eggs if the female is removed from the nest. Vocalizations Marsh Wrens are known for their loud gurgling song. Only males sing. Marsh Wren song consists of several introductory notes, a trill of repeated syllables, and usually one to several concluding notes. Songs usually last about 1-2 seconds with a highest song rate of about 20 songs per minute.
Males usually sing for extended periods in the early morning and sometimes throughout the night.
Males and females use a variety of calls including a nasal buzz given during nest building and a melodious, rolling warble used by paired males and females when they come into contact during visits to the nest. There are two major styles of singing behavior in eastern and western Marsh Wren populations. Western males are also capable of learning more songs than eastern males and devote more brain tissue to the region controlling vocal behaviors. Male Marsh Wren nestlings taken from eastern and western populations that were raised in standardized conditions still developed population specific song and neuroanatomy. Western populations have higher densities and higher rates of polygyny than eastern males, suggesting that larger repertoires and more complex songs may have been a selective advantage for western males.