Ever looked at a bird and thought, 'I wonder why birds sing...'? Find the answer to this and many more intriguing questions about birds here. How do ducks on frozen ponds stop their feet from freezing solid in winter?Do birds sleep standing up?Why do some species migrate yet others don't?And do birds have knees?Stephen Moss answers 450 questions aimed at birdwatchers of all levels, conveying a veritable feast of bird-related information in his friendly and accessible style. Drawing on up-to-date research and illustrated with more than 200 colour photos, Do Birds Have Knees? will enthral, amuse and enlighten everyone with an interest in birds.