Our house gets a bit dry in the winter with the artificial heat, so we run a humidifier in the living room for the parrots. It's on their food cart and is pointed in the direction of Calypso's cage.
The greys love to fly to his cage and sit in the stream of the humid air. They never sat on his cage door until they figured out about the humidifier.
In this last picture, you can see Calypso inside his cage, at his water dish.
Calypso does not mind if the greys are on his cage, providing they don't prevent him from entering/exiting his cage when he wants to.