A couple summers ago there was a Robin singing in my neighborhood (sort-of Georgetown) in the middle of the night.  I don't recall whether this went on for nights or weeks, but it wasn't just a single occassion.

My theory is that I was staying up too late, and the territorial male was hearing the 1:00 bird on my clock.  The real bird would sing at 3:00 - or in between - as well.

And there were a couple occassions when I discovered there were Crows roosting on the roof, when the lighting was just right and they would take off barking vociferously when the other clock's midnight Great Horned Owl called.  

The downtown Starlings seem to be active all night long.
--
Carrol Cowan 
Washington DC 
arielamcATatt.net