Systematic notes on Palearctic birds

Abstract

"In summary it can be said that, while it is convenient to arrangethe various races of Emberiza schoeniclus into three groups, theboundary between them is very arbitrary in some parts of the range.In other regions the bill characters vary a great deal individually,and it is best not to use them for subspecific discrimination, andmany races are slightly differentiated or relatively so in bothbill characters and coloration. If these, as well as those thatare purely intermediate, are eliminated, only a very few remain,namely, nominate schoeniclus, pyrrhulina, pyrrhuloides, intermedia,and korejewi. Pallidior and pyrrhulina are very far removed geographicallyand probably owe their general similarity to parallel adaptation.In view of the fact that all the races with a large, though notnecessarily identical, bill occur in the more southern and generallydrier parts of the range, the tendency towards large bills alsoseems an instance of parallel adaptation. In this connection, itis of interest to note that the forms inhabiting the most arid regionshave the largest bill of all, as in Turkestan, Seistan, the SyrianDesert, the Tarim Basin, and the Zaidam"--P. 13.