This bird was singing away today. Without the cheBECK calls, I think I could have easily mistaken it several times. It's appearance seemed to change greatly depending on the lighting and it's mood. It would sing the cheBECK from a perch, then be quiet as it flew. Just as it landed it would give a more quiet trill or double trill. Then it would resume the cheBECK. It would virtually always do the trill when it arrived at a new perch, even when it was most actively flycatching and moving from perch to perch frequently.
It's located on private property where I have permission to bird watch.