It is very likely that you have loons close by. I see and hear them often, early early in the morning at Lake Shore Park right around sunrise. The usual scenario is one Loon will call, the mate will call back. They will keep it up until they find each other.
What you most likely heard was a "locating" call that the loon experts call a "Wail". Loon sleep in the water and drift apart at night. The calls early in the morning are loons trying to find each other.
Here is an excellent site that plays the various Loon sounds and explains the meaning of the calls.
http://blog.syracuse.com/indepth/200...of_the_co.html