Common chiffchaff of grasses, bracken, nettles or similar plants. Its breeding habitat is quite specific, and even near relatives do not share it; for example, the willow warbler ("P. trochilus") prefers younger trees, while the wood warbler ("P. sibilatrix") prefers less undergrowth. In winter, the common chiffchaff uses a wider range of habitats including scrub, and is not so dependent on trees. It is often found near water, unlike the willow warbler which tolerates drier habitats. There is an increasing tendency to winter in western Europe well north of the traditional areas, especially in coastal southern England and the mild urban microclimate
Common chiffchaff criterion of the IUCN Red List (that is, declining more than 30 percent in ten years or three generations). For these reasons, the species is evaluated as "least concern". None of the major subspecies is under threat, but "exsul", as noted above, is probably extinct. There is a slow population increase of common chiffchaff in the Czech Republic. The range of at least "P. c. collybita" seems to be expanding, with northward advances in Scotland, Norway and Sweden and a large population increase in Denmark. Common chiffchaff The common chiffchaff ("Phylloscopus collybita"), or simply the chiffchaff, is a common and