A walk to the local duckpond (officially Pughs Lagoon) is a pleasant exercise for an old man. And an added pleasure is to find that the resident black swans have produced a blonde offspring. I had my pocketable camera with me to record their parental concern. But if I got too close, their quiet parental concern would turn to rage: one of them would rush at me with wings outstretched, hissing an unmistakable "Back off!" I didn't record that bit; I was backing off.

Question: If these parent birds establish a circular area, about 3-metre radius around their little treasure, into which they forbid entry, could this circle be called a cygnet ring?