I recently moved to a lake. A pair of swans had 4 cygnets we enjoyed watching. Then there were 3. Soon after one of the 3 was injured and stayed on the shore. Of course it soon disappeared. The next day I witnessed fighting between the daddy swan and another male. Upon investigating I found a dead cygnet floating in the water and a neighbor said he had watched another swan drown it. I'm now assuming that's how the injured cygnet was hurt. Is this normal behavior? Is it like African lions who will kill a male and its cubs to send the female into heat?