There are two main types of thematic collecting. The first involves using philatelic items to annotate a historical or cultural point. A collection entitled "The Slave Trade" or "Style and Syntax in Music" would be examples of this type. The second type is more prosaic-using stamps as pictures to illustrate a theme. The above set is the most expensive and popular of the Bird thematics and it is one of those sets that can easily be incorporated into either type of thematic collection. Its use as an example of the species of gull is its obvious use in a "Birds on Stamps" collection. But I have seen the set used in a Hitchcock thematic collection, and a Aviation collection as well. Thematic collecting is far more about imagination and far less about completion than traditional philately and this Monaco set is a good example of why.