Nicky likes to imagine flying like a bird; one day, his neighbor Avis tells him exactly how to become one: ""Close your eyes...let your thoughts take wing,"" and imagine growing lighter, more streamlined. ""Your heavy teeth fall out. Your jaws turn into a beak,"" and so on. As the text describes the changes that would occur, David gradually becomes a pelican, skillfully depicted in Parnall's trademark art: elegantly limned, with copious white space and angular swatches of color (here, several yellows and a rather pallid sky-blue). For the imaginative reader, it's a fairly effective way to contrast the two anatomies, with more scientific detail and less anthropomorphic drama than Joanne Ryder brings to her ""Just for a Day"" books (Catching the Wind, 1989). Not essential but attractive, and a valid supplementary approach to the subject.