GP is very right. To this day, I know that if I don't go to sleep until ~03:30, I might just as well stay up - when the birds wake and start making noise, I won't be able to sleep at all. Cars, trams, trains, I can tune out. There's something about bird chirps that makes them impossible for my brain to ignore. It's worse than loud snoring.
Interesting - I love the sound of birds and can go right back to sleep when they are chirping outside and I have the window open. Road noise on the other hand...
