The Trumpeter Swans are protected so you might want to alert your state wildlife officials to the deceased Trumpeter Swan. You might also look on the bird to see if there is any contact information on a neck or leg band to notify officials. If they say that you can remove it, we would suggest that you remove the bird and bury it appropriately. This removal should stop the mate from returning to the area and allow it to move on. The Regal Swan