For three seasons of the year, birdwatching can be a hectic sport. Spring and Autumn bring migration; Summer has the dawn chorus of frantically breeding birds. But birding in the Winter is a more subtle enterprise. Familiar birds are quiet, leaving mainly one’s sharp eyes to distinguish a fluttering movement, or a lump of not-a-dead-leaf on a bare forest branch. If you do hear birds, they are quietly murmuring to one another, not out brazenly singing in the open.