What was that?

The other day Steve looked out back and called us all to see the giant bird in our backyard.

It was flying close to the creek, below the tree branches. It had a huge wingspan, so big that it could barely get through our 'forest'. The wings were an amazing shade of blueish gray.

We think it was one of these - a great blue heron.

If so what was it doing in our little creek/forest?
Did it come up from the river?
Did it hear about our abundance of mice and voles?
Will we ever see it again?
Does anyone out there have any thoughts on what it may have been?