What do we call a young swan?

A cygnet, from the Latin cygnus by way of French - and it is grey-brown rather than white, which is the whole point of the story Hans Christian Andersen built on it. The grey is probably camouflage; adult swans are large enough not to need any.

Swans mate for long periods and often for life, and both parents raise the brood, which is unusual enough among birds to have made them a symbol. Pairs that fail to breed do sometimes separate, so the folklore is a little tidier than the behaviour.

In Britain there is a genuine legal oddity attached. The Crown has claimed ownership of unmarked mute swans in open water since the twelfth century, when they were a luxury food, and the annual Swan Upping on the Thames still takes place each July - five days of boats counting and checking the cygnets. It is now a conservation census wearing a very old costume.