From the book

“Males in neighboring territories learn their songs from one another, so when neighbors sing each has a choice as to whether he sings the same song as his neighbor or a different one.”

Listen here as two neighboring territorial males argue at their territorial boundary, counter-singing with identical songs. The contributions of the two males are easier to hear in the second half minute of this recording, as one male is in the foreground then, the other more in the background. I especially like the song at 28 seconds, as one male begins the song and the other ends it, a female also chattering in the background.

From the book

“How fascinating that the female Carolina Wren often adds a strident, buzzy chatter to his song, as females of most species let their mates sing solo.”

Listen here as the male repeats the same song over and over, the female adding her buzzy chatter where she wills.