Recently I recorded an anomalous Field Sparrow song, a trill followed by a single descending note. This differed from the usual day song, which is a series of descending notes followed by a trill (the typical "bouncing ball" song). Knowing that the Field Sparrow has a distinctive dawn song, I was intrigued to discover what the dawn song of this particular individual would sound like.
The anomalous song was sung repeatedly over a 45 minute period of observation (9.30-10.15 am, June, PA).
At dawn the bird initially sang the anomalous day song, then a bouncing ball song a few times, then switched back to its day song (4.54am).
Compare this sonagram with that of a typical day song below.
Typical bouncing ball day song (Mar, PA).
Example of a dawn song (May, DE)
So this bird sang the usual bouncing ball day song only at dawn, and sang an anomalous song the rest of the day (confirmed by follow-up visits). The anomalous song actually has a close resemblance to one version of the dawn song (compare with the middle dawn example at The Music of Nature). This bird seems to have reversed its songs, singing a dawn song during the day and the day song only at dawn.