Birds' eggs are true wonders of the natural world: they are strong enough to protect the embryo as it grows and to withstand incubation by the parent, yet sufficiently fragile to allow the chick to hatch. Little wonder that the enormous diversity of avian eggs - the amazing range of shapes, sizes, colours, textures and patterns - has long fascinated us. Since boyhood, the renowned landscape photographer Colin Prior has had a passion for wild birds...