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
Common chiffchaff collisions with windows, buildings and cars. Only the first of these has the potential to seriously affect populations, but given the huge geographical spread of "P. c. abietinus" and "P. c. tristis", and woodland conservation policies in the range of "P. c. collybita", the chiffchaff's future seems assured. The common chiffchaff has an enormous range, with an estimated global extent of 10 million square kilometres (3.8 million square miles) and a population of 60–120 million individuals in Europe alone. Although global population trends have not been quantified, the species is not believed to approach the thresholds for the population decline