Can necessarily mean “the alternation of two musical tones a diatonic 2nd apart” or “a audio resembling a musical trill.” The flute-like trill from the Wooden thrush is perhaps the most attractive track of any North American bird. The descending trill of its relative the veery isn’t too shabby, possibly. https://bookmarkrange.com/story19639675/detailed-notes-on-birdwithmostwords-com