A 2013 study showed that male Canada warblers have two performance-encoded song types. In Mode I, used mostly during the day, when unpaired either alone or near a female during early nesting, involves stereotyped songs sung slowly and regularly. Mode II, used at dawn, after pairing and when near another male, involves variable songs, sung rapidly with irregular rhythm and chippipng between songs. Most of the phrases used were common to both modes, a feature unique among paulidswhich ordinarily have an individual's repertoire separated into two distinct parts.