The Common chiffchaff (Phylloscopus collybita) is a widespread leaf warbler found throughout northern and temperate Europe and the Palearctic. It has a number of subspecies, some of which are now treated as full species. The female of this species is responsible for building a nest and assumes most of the responsibility for brooding and feeding the chicks, whilst the male has little involvement in nesting, but defends his territory against rivals, and attacks potential predators.
The Common chiffchaff is greenish-brown above and off-white below. It has dark legs, a fine dark bill, and a short primary projection (extension of the flight feathers beyond the folded wing). As the plumage wears, it gets duller and browner, and the yellow on the flanks tends to be lost. The newly fledged juvenile is browner above than the adult, with yellow-white underparts, but molts about 10 weeks after acquiring its first plumage. After molting, both the adult and the juvenile have brighter and greener upper parts and a paler supercilium (also known as an "eyebrow).
