I like that the legendary birds aren't tied to anything specific; it's neat that they're simply rare and powerful for the sake of being rare in the first place. Not every legendary needs some awesome backstory component to it.
see..that's where i disagree, not every legendary has to have an amazing life story, but it's ability's themselves should show why it is what it is. The legendary birds are just high level ice,fire and electric Pokemon. I like there design, i just fail to understand their title in the context of the story.