We live beside a lagoon here in Hawkes Bay, New Zealand, where there is a pair of black swans who chase their teenage babies away each year and only live on this lagoon themselves. At other water ways I see groups of swans so why does this pair insist on living alone in such a big area?

Second question, this morning I looked out at the pair of swans with their seven, four week old cygnets. However there were only six cygnets and one of the parents was flapping it's wings and virtually jumping up and down on the one spot. It was drowning the seventh cygnet and continued until it had succeeded. Is this behaviour normal for swans and if so why?