The Egyptian iconic script used the pictorial signifier of a sparrow as a vehicle which determines a large, heterogeneous group of words with an apparent negative meaning. Thus, the sparrow, playing the role of a semantic classifier, reflects a category in the Egyptian cognitive world.The sign is usually called the bad bird but its sphere of usage and meaning have not yet been defined exactly. The study, which originated from a German-Israeli cooperation project on Classifiers and Categorization in Ancient Egypt, draws a broad picture, from the origins of hieroglyphic writing to the beginning of the First Intermediate Period, of the dynamic process that caused a sweet, small bird, used mainly to depict inferiority (in size, age, and - later - in function, status and wealth) during the first dynasties, to acquire its negative bad bird image (disturbance, evil) by the time of the Sixth Dynasty. This mysterious shift happened by the end of the Neolithic Wet Phase, a factor that drastically changed the ecosystem of the Nile Valley. Could it be that concerns about basic, existential needs drove the Egyptians to vies with an evil eye the swarming of hungry little birds upon their crops? Hieroglyphic script represents a unique opportunity to scrutinize knowledge organization among a very ancient people, to learn the way in which the Egyptian mind perceived its world and put some order into it. (Text in French)