What is it with blue birds anyway? Why are they happier than say, a greenfinch or a corncrake?

I seem to remember a Native American story read to me (or maybe I read it to myself) way back in elementary school (that is, before I was interested in sources, and scholarly discipline) that if my memory serves honestly went something like this:

When the Great Creator first made all the birds, they were plain white-grey, and no color... I forget the bit about how the other birds got their colors... But when it came to the bluebird, it flew up into the sky and the blue color stuck to its back, which was wet (I think because he was newly made). Then, he flew down into a puddle of clay, and got the red smeared on his breast. So to this day, the Bluebird is seen as a symbol for the union of heaven and earth.

Very apropriate association with the rainbow, then, I think...

I just had a thought: In Christian Europe, the rainbow is primarily seen as an omen-cum-promise from God, and a rather grim promise it is at that:

"Won't be flood, but fire, next time."

The first link that Masato gave above gives world-wide ancient to new age symbolism of the rainbow, where it is seen as a bridge between this world and the Gods, notably in the ancient Greek and Norse mythology. Nothing about the symbolism according to the various Algonquin or Iroquois-speaking natiions that met the first settlers when they came to the American continent, but I wonder if the rainbow-as-bridge is a common motif in their myths, as well. If so, that could be one of the reasons the rainbow came to be associated with personal happiness in the American culture (and could also be where it gets its association with the bluebird...

Of course, this could be completely out in left field... haven't had coffee yet...