Okay, after double checking, it turns out there's multiple bird versions, but the one I heard was that Sedna was a beautiful but haughty woman who rejected all of her suitors until one day a new man showed up. He was handsome and charming and promised her that she'd never want for food or shelter if she married him. She agreed, they married, and then left to go to his home. When they got to his island, he revealed himself as a bird spirit and then showed her where she was going to live--while he provided for her, he gave her fish guts to eat and left her to live in a nest. Dismayed, Sedna somehow got a message home (or her father just came to check on her, I forget which) and asked her father to save her and take her home. He agreed and the two tried to escape in the kayak, but her new husband appeared and her father killed him so they could escape. However, killing the bird spirit enraged all the other birds who lived on the island too, so when Sedna and her father got out into open water, the birds swarmed them and kicked up a storm. Blaming Sedna, her father tossed her into the water in hopes that the birds would spare him, cutting off her fingers to get her to let go. So, yeah, the ending's pretty much the same once they're in the boat.

I love Sedna--there's a hell of a lot of character to her and in the end not even death could take her down.