I'm not sure. It depends on the specific context and source of 'Little Bird'. Sometimes it could be based on real events, but other times it might be purely fictional.
The 'little bird wonders story' could potentially be about a little bird's journey of discovery. It might start with the bird in its nest, looking out at the world and being filled with all kinds of curiosities. For example, it could wonder about the big, bright sun in the sky or the strange noises it hears from the forest. As it grows, it sets out to explore and find answers to these wonders, meeting different animals along the way and learning from them.
I haven't actually read this specific 'Fall, Little Wendy Bird' fanfiction. But generally, in a fanfiction, it could be about a character named Wendy who is perhaps like a little bird in some metaphorical sense. Maybe she's in a situation where she's falling, either literally or figuratively, like falling from grace or into a new and challenging situation.
I'm not sure specifically what 'little bird graphic novel' is about as there could be many with this name. It might be about a little bird's adventures, perhaps its journey in a forest, facing different animals and challenges.
Since the story is called 'little bird wonders story', the little bird is surely a main character. Depending on the plot, it could be friends with a friendly fox who helps it understand some of the things it wonders about. Or there might be an old owl that acts as a wise mentor to the little bird, answering its questions about the forest and its secrets. There could also be a family of mice that the little bird encounters during its adventures, adding more characters to the story.