Taxonomic recommendations for Western Palearctic birds: 11th report

This paper is the 11th report of the Taxonomic Sub-Committee of the BOU Records Committee. Species-level decisions are based on criteria outlined by Helbig et al. (2002). The 10th report of the Sub-Committee was published by Sangster et al. (2015).

Our review of evidence for geographic variation in the three subspecies borealis, faeroeensis and mollissima indicates that no clear subdivisions have been documented, that variation is mostly clinal, and that recognition of multiple subspecies is problematic. It seems unlikely that any of these subspecies fulfil the ‘75% rule’ of diagnosability that has been proposed as a guideline for validity of subspecies (Amadon 1949).