This work aims to present all the information available on taxonomy, morphology and distribution of Turkish songbirds, and compares it with similar data from other countries in the Middle East and Southeast Europe. Characteristics and measurements of all the subspecies of passerine birds of the region are given. Much of the data presented here was collected in the course of the 20-years" research programme for "Birds of the Western Palearctic". The author"s intention is for people to become more aware that a bird seen in Turkey or elsewhere is not just a member of a widespread species, but may form part of a discrete population with a restricted range, characterized by its own morphological features. It could form a separate unit distinguishable from other populations which, because of human interference, could become irreversibly lost. The maintenance of the world"s biodiversity is not just a matter of preserving species on a continental scale, but also conserving subspecies and populations at a local level.