Ask the Swan Specialist
Date: 1 March 2017
We are so sorry for your loss.
While looking at the wound, there appears to be a tumor or other anomaly under the swan's beak that could have caused the swan not to be able to eat. The anomaly could have been caused by cancer, an impaction/penetration wound in which the swan may have encountered a thorn, pine needle, nail, etc., that became infected. So, cancer or a bacterial infection could certainly have rendered the swan weak and unable to eat properly. Additionally, if there was any type of infection it could have caused the swan to go septic and ultimately ended the swan's life.
As far as another swan killing the bird, the injuries to the neck do not correspond with a swan attack. Swans will keep pecking in one place, usually top of the head or just below, but will not cause the stripping-like 360 degree wound (ventral and dorsal) that is seen in the photo.
If the swan was sick or dying, then it would have been easy prey for a predator. Predators such as domesticated dogs, bobcats, raccoons and coyotes will strip the neck area in a 360 degree manner. This stripping could have even been conducted immediately after the swan was dead which is why there is still blood on the fresh carcass.
Furthermore, mink, otters, soft-shelled turtles and snapping turtles and even fish could have begun eating the swan if it was floating in the water or near the bank. Without a necropsy (an animal autopsy), there is not definite explanation of how the swan died or when the predator may have attacked (i.e., before or after death). We hope that this information is of benefit to you. The Regal Swan