We have a pair of wild Mute Swans that arrived at our pond three years ago and have stayed through the Ohio winters and raised three sets of offspring. The male has developed what looks like a tumor on the side of his head. It first appeared last year then seemed to recede a bit earlier this year. But this morning I noticed his has grown immensely until it's almost the width of his head. He is quite tame and eats pellets out of my hand but they are considered invasive species in Ohio and thus I don't know how I could get him any veterinary help.

Can you provide any information? Are these frequently seen in Mute Swans? Is this likely to kill him? etc.

Thanks very much for anything you can provide.