When I was a kid I saw a movie that was about a boy who lived in the city with his single mother. One day he was taken to a magical land in the sky. In this place he father was king. The children in this land were being turned into ravens or crows by an evil being. The boys has to help save the children. ( I saw this as a kid, so my memory could be way off) thank you!!
It’s “Mio in the Land of Faraway,” made in Sweden with an international cast. The kid is an orphan living with a severe aunt, but otherwise it is as you remember it: he’s transported to the magical world his father rules but the villain is, indeed turning children into black birds.
https://en.m.wikipedia.org/wiki/Mio_in_the_Land_of_Faraway