Thus far, FOXP2 has been identified as the principal gene underlying song development through auditory feedback in vocal learning birds58, and a recent study identified a set of 67 candidate genes associated with overall differences in song between two forms of presumed vocal non-learning suboscine Empidonax flycatchers, including some associated with song nuclei expressed in vocal learning and others with speech disorders in humans57. Here, FOXP2 is linked to speech disorder.