The typical jays of the genus Garrulus number only 3 species. The Eurasian jay is polytypic and has an extensive range, while the other two, Lanceolated jay and Lidth’s jay, have relatively tiny ranges. They are characterized by similar and undoubtedly homologous blue-and-black barred feathers on the wings and/or tail. Also by traces of similar barring on the head feathers in most cases, and a strong resemblance in movements, ecology and voice.
They appear most closely related on one hand to the green and blue magpies of the genus Cissa and on the other to the boreal jays of the genus Perisoreus, to which they seem to be linked by the Sooty jay P. internigrans. Over the greater part of their combined ranges the species of Garullus are completely allopatric but the Eurasian jay and the Lanceolated jay overlap in the Western Himalayas.
The Eurasian jay has a much more extensive range than either of its congeners. Within its range it shows considerable geographic variation. Some populations now appear to be completely isolated from their nearest relatives by sea or unsuitable terrain. As, however, at least as far as their taxonomic characters are concerned, the most divers forms are connected by intergrades and no instance is known of two forms coming together and not interbreeding to form a mixed population, they seem best all treated as members of a single polytypic species.
Within each major group of the more diverse forms, numerous races (or one might better say micro-races) of the jay have been named and recognized. Sometimes, it seems, those who have done so had an ability to recognize geographical variation in inverse relation to their ability to recognize individual variation. However, the numerous races within the species can be divided in five comprehensive major racial groups.