Jetlagged Birds?

Strange how you notice something that just does not seem right...for 2 nights in a row, when it is pitch black outside and around midnight or later there have been 2 birds in my back garden wide awake and chirping away as if it were the middle of the day in Spring. It really threw me off. I usually go to bed and I can hear some traffic in the distance, maybe a drunk on the street singing, etc but birds chirping is what I hear when I wake up in the morning...not at midnight. Totally bizarre. I figured they must be jetlagged!