Alps no Shoujo Heidi was a Japanese animated series based on the popular Heidi series of books. English Title: Heidi, A Girl of the Alps
Heidi is confronted with the hard reality of Picchi migrating with its kind. Moreover, she gets angry at Peter because the boy thinks that Picchi has left because the bird doesn't love her anymore. Onji calms her down, takes her for a walk and explains to the girl that Picchi needs a warmer place to spend the winter. Peter catches a bird for Heidi to make up with her. The kids become friends again but Heidi decides to free the bird so it can migrate too and isn't left behind alone.