Siberian chiffchaff to be a full species due to its distinctive plumage and vocalisations, being similar to "P. s. sindianus" in these respects. Common chiffchaffs (of the nominate race) and Siberian chiffchaffs do not recognize each other's songs. Pending resolution of the status of the form "fulvescens", which is found where the ranges of common chiffchaff (of the race "abietinus") and Siberian chiffchaff connect and may or may not be a hybrid between these, "tristis" is maintained in "P. collybita" by most checklists. Siberian chiffchaff Siberian chiffchaff ("Phylloscopus (collybita) tristis") is a leaf-warbler which is usually considered a subspecies of the common
Handbook of the Birds of the World a non-profit endeavour fuelled by material from more than one hundred contributors from around the world. In early 2013, Lynx Edicions launched the online database HBW Alive, which includes the volume and family introductions and updated species accounts from all 17 published HBW volumes. Since its launch, the taxonomy has been thoroughly revised and updated twice (once for non-passerines and once for passerines), following the publication of the two volumes of the "HBW and BirdLife International Illustrated Checklist of the Birds of the World". The Handbook of the Birds of the World Alive site also provides a free access 'Key