Species limits in Northern Eurasian taxa of the common stonechats, Saxicola torquatus complex (Aves: Passeriformes, Muscicapidae)

The common stonechat Saxicola torquatus traditionally was considered as a polytypic species widely distributed in Africa, Europe and Asia. Recently, several authors have suggested that this formerly single species needs to be split into several distinct species composing the Saxicola torquatus complex based on mitochondrial markers. However, mitochondrial DNA alone is not sufficient for the evaluation of species status. In this paper, we reviewed the taxonomy of Northern Eurasian taxa from the complex based on morphometrics, plumage, song and alarm calls. The morphological and vocal data clearly matched the phylogroups reconstructed from mitochondrial DNA sequences, and separated Northern Eurasian taxa of the Saxicola torquatus complex into three groups: rubicola, maurus and stejnegeri. We proposed the species status for these three groups: European stonechat Saxicola rubicola, eastern stonechat Saxicola maurus and Japanese stonechat Saxicola stejnegeri. Among them, S. stejnegeri is a cryptic species as it cannot be distinguished by morphometrics and by worn spring plumage from S. maurus, but differs noticeably by male song.