El Cajon Parrot Roost Empty

I made a trip to the El Cajon Parrot Roost hotspot this evening, but was disappointed to find no parrots roosting there.  Hundreds flew over the courthouse and the surrounding trees, but continued east to points unknown, out of view and out of earshot.  I was on the roof of the parking structure, and it appeared they were traveling quite a distance from there.  I waited until dark to make sure they didn’t all come flying back last minute. Maybe this is a seasonal thing? Maybe one of you knows where they go this time of year? Or maybe they have two roosts?  Just a heads up that they aren’t always in the courthouse trees.