How do the swans relate in Good Neighbors?
Animal transformation is one aspect of both faerie folklore and also faerie tales. Animal transformation like a person who transforms into an animal, animal transforms into a person, is one of the universal motifs of folklore, it’s all over the world. Different animals often, but tales of this kind are pretty universal.
In Good Neighbors its swans that transform and they transform by basically taking off a cloak of feathers and the cloak of feathers allows them to become swans. If some one has a cloak of feathers, as in the Sulky legend where sulkies are seals who take off their skins and if some body posses their skin, they control them and they cannot go back to being sulkies/seals, they cannot go swim with other sulkies, they wind up staying on land and its one of the common ways of capturing and controlling them.
In the story [Good Neighbors] the swan cloak functions in the same way where they [the swans] possessed and by possessing the cloak, they are possessed by that person.