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
Handbook of the Birds of the World to Scientific Names in Ornithology'. A list of volumes of the "Handbook of the Birds of the World" produced to date is as follows: This volume was published in 1992. Unlike subsequent volumes, it does not have an introductory essay; instead, it has a 38-page overview by Eduardo de Juana of the biology of birds and a foreword welcoming the HBW project, by Christoph Imboden. Groups covered in this volume are as follows: This volume was published in 1994. It has a foreword by Walter J. Bock on the organization of information in HBW. Groups covered in this volume are