Colour-categories of male Pied flycatchers in spring

Abstract

Professor Rudolph Drost was the first to devote full attention to this theme. in the numerous male Pied Flycatchers Ficedula hypoleuca on sprinq migration on Heliqoland the upper-parts showed considerable variation in colour. While in some males the upper-part was black throughout, others lacked black almost completely. Drost examined 237 skins from North and Central Europe, and worked out 7 colour-categories for classification. At the same time he was aware of the fact that more or different categories might be chosen. However, in the meantime these 7 categories have been generally accepted and proved to be practical.