Birdsong -- Innate or Learned?
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The willow flycatcher's song is overwhelmingly innate, while the mockingbird uses innate patterns, learned songs, mimicry, and improvisation in its repertoire.

Chris Tenney recorded the Northern mockingbird, the Pacific slope flycatcher, and the house finch in or around Salinas. The song of the willow flycatcher can be found on the CD Bird Songs of California produced by the Cornell Laboratory of Ornithology.