The swan is probably a juvenile swan that was dispatched by its parents from their habitat so the young swan will find a mate and start its own habitat/family.

The swan is actually a Trumpeter or Tundra Swan. We cannot see the space between the eye (called the lore) to see if it is yellow. If there is a yellow lore, then it is a Tundra Swan, if it does not have a yellow lore, then it is a Trumpeter Swan. The Regal Swan