Sesame Street Presents: Follow That Bird(1985)
When a pesky social worker thinks Big Bird should be with his own kind (other birds) instead of living on the diverse Sesame Street, she sends him to a foster with a family of Dodos, but he is not happy and runs away. Big Bird begins a long adventure wandering the country. In the mean time, his friends search for him to bring him back.
The audio is a little out-of-synch on this theatrical trailer.