Hi Dee,

Here in San Diego the Nightingale and the Mockingbird sing in the middle of the night.  Actually their songs are such beautiful sounds.  There maybe one bird that starts and then you can hear another one further away responding.   I am often up late in the night and as I stand on my porch I can hear them and really delight in their songs. 
http://www.birdwatching.com/stories/mockingbird.html

Another one of God's gift to us when we need some beauty in our lives.  If you get the chance go out when you hear one bird singing and listen carefully for another one responding way out, they sometimes repeat the same song as the "lead-bird", enjoy them they are truly soothing.

God Bless,
Barbara