Why do birds have feathers? This book doesn't know.
It's a weird story. I guess it's based on an Iroquois legend. Basically, once upon a time, birds had no feathers. (Somehow they were able to fly, nonetheless. We're not really sure how.) They were just always naked and pink. They didn't really mind, but when they realized all the other animals were making fun of them, they called on the Great Spirit, "as our friends the Indians do," you know, "Please give us coverings!" and the Great Spirit said, "Go get them! They're on Feather Mountain, waiting for you!" And the turkey buzzard flies to Feather Mountain and picks a very colorless suit because he can fly very far with it, and brings a bunch of feathers back to his friends, and they all argue about who should get which feathers. Then they do it methodically and pick feather coverings that will help them hide. And that's the end.
There's not really much to it. There's definitely no message to it. There's a story, and a plot, but really no point. There's no moralizing to it, but also no indication of why this happened to the birds. Just that at some point they didn't have feathers, and then they had feathers. Ta-da.