The Common Chiffchaff or simply Chiffchaff, Phylloscopus collybita, is a common and widespread leaf warbler, named for its distinctive onomatopoeic song, which breeds in open woodlands throughout northern and temperate Europe and Asia.
It is a migratory passerine which winters in southern and western Europe, southern Asia and north Africa. Greenish-brown above and off-white below, it is named for its simple chiff-chaff song. It has a number of subspecies, some of which are now treated as full species. The female builds a domed nest on or near the ground, 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.
A small insectivorous bird, it is subject to predation by mammals, such as cats and mustelids, and birds, particularly hawks of the genus Accipiter. It may also acquire external or internal parasites. Its large range and population mean that its status is secure, although one subspecies is probably extinct.
Described by German zoologist Heinrich Boie in 1826, the genus Phylloscopus contains about 50 species of small insectivorous Old World woodland warblers which are either greenish or brown above and yellowish, white or buff below. The genus was formerly part of the Old World Warbler family Sylvidae, but has now been split off as a separate family Phylloscopidae. The Chiffchaff's closest relatives, other than former subspecies, are a group of leaf warblers which similarly lack crown stripes, a yellow rump or obvious wing bars; they include the Willow, Bonelli's, Wood and Plain Leaf Warblers.
The Chiffchaff is a small, dumpy, 10–12 centimetres (4 in) long leaf warbler. The male weighs 7–8 grammes (0.28–0.31 oz), and the female 6–7 grammes (0.25–0.28 oz). The spring adult of the western nominate subspecies P. c. collybita has brown-washed dull green upperparts, off-white underparts becoming yellowish on the flanks, and a short whitish supercilium. It has dark legs, a fine dark bill, and 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, but after the breeding season there is a prolonged complete moult before migration. The newly-fledged juvenile is browner above than the adult, with yellow-white underparts, but moults about 10 weeks after acquiring its first plumage. After moulting, both the adult and the juvenile have brighter and greener upperparts and a paler supercilium.
This warbler gets its name from its simple distinctive song, a repetitive cheerful chiff-chaff. This song is 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 djup djup djup wheep wheep chittichittichiittichitta. However, mixed singers occur in the hybridisation zone and elsewhere, and can be difficult to allocate to species.
When not singing, the 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 and generally pale legs. Bonelli's Warbler (P. bonelli) might be confused with the eastern Chiffchaff subspecies tristis, but it has a plain face and green in the wings. The Chiffchaff also has rounded wings in flight, and a diagnostic tail movement consisting of a dip, then sidewards wag, that distinguishes it from other Phylloscopus warblers and gives rise to the name "tailwagger" in India.
Perhaps the greatest challenge is distinguishing non-singing birds of the nominate subspecies from Iberian Chiffchaff in the field. In Great Britain and the Netherlands, all accepted records of vagrant Iberian Chiffchaffs relate to singing males.
The Chiffchaff breeds across Europe and Asia east to eastern Siberia and north to about 70oN, with isolated populations in northwest Africa, northern and western Turkey and northwestern Iran. It is migratory, but it is one of the first passerine birds to return to its breeding areas in the spring and among the last to leave in late autumn. When breeding, it is a bird of open woodlands with some taller trees and ground cover for nesting purposes. These trees are typically at least 5 metres (16 ft) high, with undergrowth that is an open, poor to medium mix 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 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 of London. These overwintering Chiffchaffs include some visitors of the eastern subspecies abietinus and tristis, so they are certainly not all birds which have bred locally, although some undoubtedly are.
The male Chiffchaff is highly territorial during the breeding season, with a core territory typically 20 metres (66 ft) across, which is fiercely defended against other males. Other small birds may also be attacked. The male is inquisitive and fearless, attacking even dangerous predators like the stoat if they approach the nest, as well as egg-thieves like the Eurasian Jay. His song, given from a favoured prominent vantage point, appears to be used to advertise an established territory and contact the female, rather than as a paternity guard strategy.
Beyond the core territory, there is a larger feeding range which is variable in size, but typically ten or more times the area of the breeding territory. It is believed that the female has a larger feeding range than the male. After breeding has finished, this species abandons its territory, and may join small flocks including other warblers prior to migration.
The clutch is two to seven (normally five or six) cream-coloured eggs which have tiny ruddy, purple or blackish spots and are about 1.5 centimetres (0.6 in) long and 1.2 centimetres (0.5 in) across. 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 three to four weeks, and are fed by and roost with the female, although these interactions reduce after approximately the first 14 days. In the north of the range there is only time to raise one brood, due to the short summer, but a second brood is common in central and southern areas.
Although pairs stay together during the breeding season and polygamy is uncommon, even if the male and female return to the same site in the following year there is no apparent recognition or fidelity. Interbreeding with other species, other than those formerly considered as subspecies of P. collybita, is rare, but a few examples are known of hybridisation with the Willow Warbler. Such hybrids give mixed songs, but the latter alone is not proof of interspecific breeding.
The Chiffchaff is occasionally a host of brood parasitic cuckoos, including the Common and Horsfield's Cuckoos, but it recognises and rejects non-mimetic eggs and is therefore only rarely successfully brood-parasitised. Like other passerine birds, the Chiffchaff can also acquire intestinal nematode parasites and external ticks.
The main effect of humans on this species is indirect, through woodland clearance which affects the habitat, predation by cats, and collisions with windows, buildings and cars. Only the first of these has the potential to seriously affect populations, but given the huge geographical spread of P. c. abietinus and P. c. tristis, and woodland conservation policies in the range of P. c. collybita, the Chiffchaff's future seems assured.
None of the major subspecies is under threat, but exsul, as noted above, is probably extinct. The range of at least collybita seems to be expanding, with northward advances in Scotland, Norway and Sweden and a large population increase in Denmark.