The neurological disease could be Botulism. Did your pond have a drawdown due to drought then an increase in rain? If so, this might be the reason. The bird scavenging in the muck got into an area that he normally could not reach and found the anerobic bacteria clostridium. These bacteria cause a toxin botulism to be produced which affects the neurological system.

Without a necropsy, you would not be able to positively determine if this was the case. If the drawdown is still prevalent or you are getting heavy rains, there is a possibility that the female may have the same thing happen to her if she comes into contact with the bacteria. If the drawdown has cleared and no more heavy rains, then the female swan should be fine until you can move her to the next pond.

However, all ponds/lakes have the propensity to house the clostridium botulinum bacteria, so you should have the swan vaccinated against the toxin.

If you would like to have her vaccinated, you will need to contact Ask The Swan Specialist at this page and the website administrator will get back to us. We will have our swan veterinarians speak with your veterinarian regarding the vaccine and dosage. The Regal Swan