The book's subtitle - A study of an ecological interaction - properly reflects the author's theme but may tend to hide the fact that the relationships between birds and berries can be much more than the simple, mutually advantageous systems ('eat my fruits, spread my seeds') they may seem at first to be. Therein lies the core of the book - the less obvious intricacies and impications of plant/bird associations, the coevolution of species in some cases and the adaptation of a species (bird or plant) to further its own advantage. To complicate the scene, too, there are the 'exploiters', the pul.