Ask the Swan Specialist
Date: 20 April 2017
Thanks for the reply. Seems unlikely that two different swans would suffer injuries to both eyes, but yes there are turtles present, and plants growing on the banks, but no metal that I know of. Removing turtles is a never ending job around here, but I do my best. I'm still holding out hope there won't be a carcass in this most recent incident, but if it dies I plan on having someone qualified do a necropsy.
I'm no expert but I think it is more likely it is either some type of poisoning, or a disease. I have some chickens that have experienced mareks disease, which can affect the eyes in chickens, but I was unable to learn how it might affect swans, which I have read can get it. I also read that lead poisoning might cause blindness and shooting a .22 rifle around the pond may have been used for turtle control, but I wouldn't think a 10-day old swan would swallow lead that size and still be alive. I have read that lead shot is a serious hazard for waterfowl, but I'm pretty sure no shotguns have been fired around the ponds. There is also the possibility of food getting moldy due to all the Spring rain. I feed chicken pellets and scratch grain. I know molded food can kill swans, but can it also blind and not kill? I also have koi in the pond and feed a higher protein pellet to the koi than the swan should get. Sometimes the swans eat the koi pellets. Can this cause blindness? It hasn't been a problem for my other swans. I'll post a picture of the black neck that died, both eyes looked similar to this photo. Neither eye looked damaged from being scratched or anything like that.
I'd still like to try and save the baby, but preventing this from happening again is the most important thing.