The common chaffinch is about 14.5 cm long, with a wingspan of 24.5–28.5 cm and a weight of 18–29 g .
The adult male of the nominate subspecies has a black forehead and a blue-grey crown, nape and upper mantle. The rump is a light olive-green; the lower mantle and scapulars form a brown saddle. The side of head, throat and breast are a dull rust-red merging to a pale creamy-pink on the belly. The central pair of tail feathers are dark grey with a black shaft streak. The rest of the tail is black apart from the two outer feathers on each side which have white wedges. Each wing has a contrasting white panel on the coverts and a buff-white bar on the secondaries and inner primaries. The flight feathers are black with white on the basal portions of the vanes. The secondaries and inner primaries have pale yellow fringes on the outer web whereas the outer primaries have a white outer edge.
After the autumn moult, the tips of the new feathers have a buff fringe that adds a brown cast to the coloured plumage. The ends of the feathers wear away over the winter so that by the spring breeding season the underlying brighter colours are displayed. The eyes have dark brown irises and the legs are grey-brown. In winter the bill is a pale grey and slightly darker along the upper ridge or culmen, but in spring the bill becomes bluish-grey with a small black tip.
The adult female is much duller in appearance than the male. The head and most of the upperparts are shades of grey-brown. The underparts are paler. The lower back and rump are a dull olive green. The wings and tail are similar to those of the male. The juvenile resembles the female.
Males typically sing two or three different song types, and there are regional dialects also
Distribution and Habitat
The common chaffinch breeds in wooded areas where the July isotherm is between 12 and 30 °C. The breeding range includes northwestern Africa and most of Europe and extends eastwards across temperate Asia to the Angara River and the southern end of Lake Baikal in Siberia. There are also a number of distinctive subspecies on the Azores, the Canary Islands and the Madeira Islands in the Atlantic Ocean.
This bird is not migratory in the milder parts of its range, but vacates the colder regions in winter. It forms loose flocks outside the breeding season, sometimes mixed with bramblings.
Outside the breeding season, common chaffinches mainly eat seeds and other plant material that they find on the ground. They often forage in open country in large flocks. Common chaffinches seldom take food directly from plants and only very rarely use their feet for handling food.
During the breeding season, their diet switches to invertebrates, especially defoliating caterpillars. They forage in trees and also occasionally make short sallies to catch insects in the air. The young are entirely fed with invertebrates which include caterpillars, aphids, earwigs, spiders and grubs (the larvae of beetles).
Common chaffinches first breed when they are 1 year old. They are mainly monogamous. The date for breeding is dependent on the spring temperature and is earlier in southwest Europe and later in the northeast. A male attracts a female to his territory through song.
Nests are built entirely by the female and are usually located in the fork of a bush or a tree several metres above the ground. The nest has a deep cup and is lined with a layer of thin roots and feathers. The outside is covered with a layer of lichen and spider silk over an inner layer of moss and grass. The eggs are laid in early morning at daily intervals until the clutch is complete. The clutch is typically 4–5 eggs, which are smooth and slightly glossy, but very variable in colour. They range from pale-blueish green to light red with purple-brown blotches, spots or steaks. The average size of an egg is 19 mm × 15 mm with a weight of 2.2 g. The eggs are incubated for 10–16 days by the female.
The chicks are altricial, hatching nearly naked with closed eyes, and are fed by both parents but mainly by the female, who broods them for around six days. They are mainly fed caterpillars. The nestlings fledge 11–18 days after hatching and disperse. The young birds are then assisted with feeding by both parents for a further three weeks. The parents only very rarely start a second brood, but when they do so it is always in a new nest. Juveniles undergo a partial moult at around five weeks of age in which they replace their head, body and many of their covert feathers, but not their primary and secondary flight feathers. After breeding adult birds undergo a complete annual moult which lasts around ten weeks.
The common chaffinch has an extensive range, estimated at 7 million square kilometres and a large population including an estimated 130–240 million breeding pairs in Europe. Allowing for the birds breeding in Asia, the total population lies between 530–1,400 million individuals. There is no evidence of any serious overall decline in numbers, so the species is classified by the International Union for Conservation of Nature as being of Least Concern.