There I was in the Gran Chaco. It was sunset and a flock of hundreds of parrots were screeching in two trees nearby. The noise was darn near deafening. Then, the sun set. And on cue, the birds stopped their noise. It happened instantaneously, just as though I had turned off a switch. It was time to go to sleep, obviously.
“...just as though I had turned off a switch. It was time to go to sleep, obviously.”
We got the opposite problem in the cities. Birds are programmed to be quiet at night (except for mockingbirds), but since cities have streetlights and other lights on all the time, the birds get confused and sometimes chirp away all night long.