Der Löwe und der Vogel(1983)

The bird moves to the south in autumn and sings his most beautiful song to the lion there. When he flies back to the north, the lion sets off on the long journey to look for his friend. He gets to the city and gets into captivity. The bird finds him and sings his song to him again. This happiness does not last long, because it is autumn and the bird is moving back to the south. The unfortunate lion is left in his cage.