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Age‐related song variation in male barn swallows

Abstract The hypothesis that song rate and song features of male barn swallows (Hirundo rustica) reflect age, a quality useful in assessment contexts, was tested in the present correlational study. The differences were analyzed between song rate and seven variables describing song structure in male barn swallows of differing age. Yearling males produced shorter songs, used a lower number of syllable types in their songs, and never repeated the same syllable sequences. In contrast, older males used more syllable types in the songs, and emitted longer songs that appeared to be more crystallized. Song also varied over the individual's lifetime since song duration increased between two consecutive breeding seasons. Thus, some song features appeared to function as age‐markers enabling females to distinguish yearlings from older males.