Listening to a Continent Sing

A Nashville warbler singing at dawn. It is the same song over and over, two-parted, seebit seebit seebit tititititititi, suggesting that a Nashville warbler neither has a special dawn song nor chips sharply between songs. Perhaps he shows some special excitement by singing a little more rapidly during the dawn chorus than later in the day.

At 1:47 he mutes a few phrases of what seems an entirely different song, then stops. What's that all about? And at other times he begins his song with some of these muted notes (e.g., 1:13), then reverts to his robust seebit titi song. Is this some measure of excitement that he shows during the dawn chorus? I wish I understood better the difference between dawn and daytime singing in this species.

Background

A black-headed grosbeak sings continuously in the distance, more closely from 1:02 to 1:11; spotted towhee, yellow warbler

Photo by John Van de Graaff