While out listening to birds this morning in Philadelphia, I heard a call above me that at first I thought was a very early migrant Yellow-rumped Warbler. On closer observation it turned out to be a male Scarlet Tanager. I've heard this call by Scarlet Tanagers before, but this is the first time I've recorded it. It sounds remarkably similar to the chup call note of the Yellow-rumped (Myrtle) Warbler, and appears to be used as an alarm call.
Yellow-rumped (Myrtle) Warbler call (Nov, NJ).
This call is not the chick part of the chick-burr alarm call, which has a different appearance on the sonagram: