Cleverly and charmingly illustrated, these toddler picture books introduce the concept of things not being always what they seem to be, quite a difficult one for the literal brain of the typical toddler to grasp. The tale is a search for the eponymous duck, parts of which appear to be visible through cutouts in each alternate page (“Is that her tail behind the tractor?”), but which then turn out to be parts of another creature or object. The illusions are usually excellent. The duck is eventually revealed with all her ducklings. (Not to be confused with the much simpler That’s Not My…” family of baby touchyfeely books.) Also in the series are the equally good Where’s That Monkey?, Where’s That Fish? and Where’s That Cat? Ages 2 and up.