Turtles go in the water, tortoises don't. That was what I was taught.
As for symbols, if you are going symbol it should only be a symbol. I don't like switching back and forth much.
Is the tortoise and hare parable widespread enough to use them? The contrast would be much more natural for anyone familiar with the story.
Birds could stand for flight, air, waking me up at sunrise, all kinds of things.