Everybody's Egg by Susan & Wendy Mitchell

Ivy goes out for a walk one breezy day, only to find a very tall tree with something small and white, wobbling in a dip at the top. She becomes worried when the small white object topples over the side, heading straight for the hard ground below. Until, that is, the tiny creatures that live in the tree save the day, working together to save something precious and fragile. The strange thing is this special, natural sort of magic just seems to vanish – poof! – the moment a grown-up lays eyes on it…