The male feeds the chick and I wondered if this one was feeding a cuckoo - the nestling seems a different shape to the adult and doesn't have the pink beak or streaking of the adult either. But then I just wondered if the juvenile is a female?
Re the nest, i haven't been able to photograph a bird going into it but the bird that owns it is the same size and shape as the oriole so I think this might be the oriole nest - photographed a few days before