Cactus wren
Chapter 6: Song Learning Often Creates Complex Songs and Large Repertoires
Subchapter: Song complexity
From page 80 in the book.
Photo by John Van de Graaff
♫369. Singing adult male, consistently delivering the same song throughout, with a second bird, perhaps a young bird, heard twice (at 1:59 and 2:41). March 22, 2017. Anza Borrego Desert State Park, Borrego Springs, California. (7:57)