phrase of two parts:
- first part consisting of a monotone or slightly ascending trill, moderate speed. Trill equal to a twitter, very slightly buzzed, mostly clear tones;
- second part, executed immediately after first part, higher pitched, ascending, variable warble of slightly shorter duration than first part (warble = more than two tones) consisting of a variable ascending trill.
Anyway, the Yellow-rumped Warbler changed its song! After singing the same song for an hour, it changed, seemingly, in response to my play-back! The first part was noticeably higher pitched and definitely ascending and the second part was even shorter than before. Then this new version, Song B, slowly evolved back into Song A, with the second part going back to the Song A sooner than the first part. It repeated Song A again several times, then burst into song B, which again morphed back to song A over several repetitions.
Today, as I sit writing this, with my office window open, a Yellow-rumped Warbler is calling from a nearby fir tree.
Is it singing the exact same song as the one in the park yesterday? No, not really! This song is not in two discernable parts - the monotone trill grading into a more warbling ascending trill at the end. This one is more just a single phrase with the whole thing starting with the monotone trill, upwards, to end in almost individual cheeps. What can I say - it's hell to be detail oriented, and probably boring to read.