Common chiffchaff one of the first avian signs that spring has returned. Its call is a "hweet", less disyllabic than the "hooeet" of the willow warbler or "hu-it" of the western Bonelli's warbler. The song differs from that of the Iberian chiffchaff, which has a shorter . However, mixed singers occur in the hybridisation zone and elsewhere, and can be difficult to allocate to species. When not singing, the common chiffchaff can be difficult to distinguish from other leaf warblers with greenish upperparts and whitish underparts, particularly the willow warbler. However, that species has a longer primary projection, a sleeker, brighter appearance
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