I volunteer at a local park in Florida. We have a small lake with approx. 50-55 swans (mostly mute, a few whooper, a few black, one trumpeter & one black necked)
We have lost a large percentage of cygnets this nesting season. Some have just disappeared, some have died with no obvious signs of injury. (lethargy, won't eat, drink and looks right through you) I have observed with one clutch in particular that the female constantly shakes her head and I hear a rattle sound. One of her babies is sick and is displaying similar behavior. Two other of the babies in the same clutch are beginning to shake their heads. Please advise?