Some feathered crooners may advertise their size to females by hitting the low notes. Ornithologists at the Max Planck Institute found that only bigger-bodied birds belt out the  bass.

The physical size of some birds may put a limit on the frequency of the birds’ songs, according to a study published in PLOS ONE. Since only a larger males hit lower notes, females may be able to use deeper voices as a reliable measure of a male’s size. Size matters to some songbird species, with females preferring larger males, so vocal limitations could affect some birds’ love lives.

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The songs of  purple-crowned fairy-wrens, Malurus coronatus coronatus, hit a range of notes. However the study found that in some songs, larger body size related to lower-pitched singing ability.

Further study will be needed to prove a relationship among body size, singing frequency and sexual success in fairy-wrens. The authors suggested that body size may be just one of many characteristics advertized by fairy-wrens songs.

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The authors also noted that low-frequency singing ability may have resulted from good health as the male fairy-wrens grew up. Better health may have allowed better development of singing structures in the birds’ anatomies. The same healthy conditions could have also resulted in larger size. So size and singing would be correlated, but not causally related.

IMAGE: Malurus coronatus (Malurus coronatus, Wikimedia Commons)