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
The Life of Birds matter had been covered before by Attenborough within "Life on Earth", in an episode entitled "Lords of the Air", but now he was free to expand on it. However, by his own confession, despite being especially fascinated by one family, the birds of paradise, Attenborough was not an expert in ornithology. Nevertheless, the notion of an entire series devoted to the creatures excited him, as he would be able to not only communicate his findings to the viewing audience, but further his own knowledge as well. From the outset, the production team were determined that the sound of birds calling