They could have been blown off the migratory path and need to rest. If people are feeding them, they may want to stay instead of leaving. Do they look hurt? Is there a pond nearby?

Because many state wildlife officials want to see them killed and gave threatened wildlife rehabilitation centers and veterinarians with the loss of their license if they do not allow them to die (offer) no help or euthanize them, you may need to quietly ask around to see if someone can capture, examine and treat them if necessary. They may just need to get some food, rest and get out of the cold for a couple of days. We're not sure if your state has the kill all Mute Swan policy. You might be fortunate to find someone to help by asking various no kill animal/wildlife shelters about their policies. Please let us know how this situation works out for the swans. The Regal Swan