The social role of the male red-winged blackbirds' Ageliaus phoenicetts, advertising song was examined. Territorial male red-wings were captured on their territories and subjected to bilateral sectioning of the hypoglossal nerves where they descend along the trachea. This surgery resulted in males which delivered species atypical songs at the times when they attempted to sing the normal advertising song. A group of control males were captured and treated in the same way as the surgically treated males except the hypoglossal nerves were not sectioned. The following results were obtained: 1) Vocalization altered males were successful in maintaining territories for the remainder of the breeding season. 2) Vocalization altered males were able to mate with females and raise young successfully. 3) Five vocalization altered males returned to the same marsh the following breeding season, one year after the operation and successfully established and maintained territories. It was concluded that the ability to deliver species typical song was not necessary for the establishment and maintenance of a breeding territory under the environmental conditions encountered during these experiments.