The Common chiffchaff is a widespread insectivorous songbird found in Europe, Asia, and Africa. Greenish-brown above and off-white below, this small bird is named for its simple chiff-chaff song. 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).
Common chiffchaffs breed across Europe and Asia, with isolated populations in northwest Africa, northern and western Turkey, and northwestern Iran. They are migratory birds that winter in southern and western Europe, southern Asia, and North Africa. Their breeding habitat includes open woodlands with some taller trees and ground cover for nesting purposes. In winter, Common chiffchaffs use a wider range of habitats including scrub, willow thickets, and are often found near water. They also frequent parks, gardens, hedgerows, and cultivated areas.
Common chiffchaffs are active diurnal birds. They are generally solitary but may join small flocks including other warblers prior to migration. Chiffchaffs forage both on the ground and in bushes, low vegetation, and trees, moving restlessly through foliage or briefly hovering. They may even pick insects from the water surface. These small birds require about one-third of their weight in insects daily, and they feed almost continuously in the autumn to put on extra fat as fuel for the long migration flight. Common chiffchaffs are among the last songbirds to leave in late autumn and are one of the first to return to their breeding areas in the spring and their repetitive cheerful 'chiff-chaff' song is one of the first signs that spring has returned. Their common call is a soft and simple 'hooeet' or 'hweet' and mates communicate with each other using short 'drit' or 'it'.
Common chiffchaffs are serially monogamous meaning that they form pairs that stay together only during one breeding season which occurs between April and early August. The males typically return to their breeding territory two or three weeks before the females and immediately start singing to establish ownership and attract a female. During this time males are highly territorial and fiercely defend their territory against other males. When a female is located, the male will use a slow butterfly-like flight as part of the courtship ritual, but once a pair-bond has been established, other females will be driven from the territory. The female builds her nest alone on or near the ground in a concealed site in brambles, nettles, or other dense low vegetation. The domed nest has a side entrance and is constructed from coarse plant material such as dead leaves and grass, with finer material used on the interior before the addition of a lining of feathers. The clutch is 2-7 cream-colored eggs that have tiny ruddy, purple or blackish spots. They are incubated by the female for 13-14 days before hatching as naked, blind altricial chicks. The female broods and feeds the chicks for another 14-15 days until they fledge. The male rarely participates in feeding, although this sometimes occurs, especially when bad weather limits insect supplies or if the female disappears. After fledging, the young stay in the vicinity of the nest for 3 to 4 weeks, and are fed by and roost with the female. Reproductive maturity is typically achieved at one year of age. In the north of the range, chiffchaffs raise only one brood, due to the short summer, but a second brood is common in central and southern areas.
Common chiffchaffs are considered threatened globally, however, as with most small birds, mortality in the first year of their life is high. Eggs, chicks, and fledglings of this ground-nesting species are taken by stoats, weasels, and crows, and the adults are hunted by birds of prey, particularly the sparrowhawk. Small birds are also vulnerable to the weather, particularly when migrating, but also on the breeding and wintering grounds. Common chiffchaffs also suffer from woodland clearance which affects the habitat, predation by cats, and collisions with windows, buildings, and cars.
According to the IUCN Red List, the total population size of the Common chiffchaff is 10,000,000-500,000,000 mature individuals. In Europe, the breeding population consists of 41,000,000-59,500,000 pairs, which equates to 81,900,000-119,000,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are increasing.