The British or European Robin, erithacus rubecula

The North wind doth blow and we shall have snow,
And what will poor robin do then, poor thing?
He’ll sit in a barn and keep himself warm
and hide his head under his wing, poor thing.

– traditional nursery rhyme

The robin is particularly associated with Christmas and is a popular image for Christmas cards.  This is probably because the robin is one of the few British birds to sing all year round.  Its song from mid-December into spring is particularly strong, as males seek to defend territory and attract a mate.