The diet of the common redpoll is primarily composed of small seeds, such as those of birch, willow and alder, as well as conifers, grasses and weeds. It also eats other plant parts, including buds, shoots, leaves, fruit and catkins, as well as some invertebrates in summer (2) (3) (4) (5). Nestling common redpolls are fed mainly on soft-bodied invertebrates, although in some areas they are reportedly fed almost entirely on the seeds of cottongrass (Eriphorum species) (2) (5).
The common redpoll commonly feeds in trees, often at the outer extremities, where it hangs upside-down to reach buds and catkins (2) (4) (5). It also searches trees and shrubs for insects, and may cling to thin stems in low vegetation to reach seeds (5). In winter, the common redpoll often feeds on the ground (2) (5) and will also visit bird feeders (4).
As an adaptation against harsh northern environments, the common redpoll is capable of storing food in an expandable area within its throat, providing a reserve that can be consumed later in a more protected spot or during long winter nights (2) (5). The common redpoll’s dense, fluffy plumage provides good insulation (4) (5), while its body is feathered in areas that are bare in most other birds, giving further protection against the cold (4). In winter, the common redpoll sometimes tunnels into snow to roost, with the snow insulating the bird against the cold night air (4).
A gregarious species, the common redpoll is usually found in pairs or small to large flocks (3) (4). At popular roosting sites, flocks of around 1,000 individuals have been known to form (5), and several pairs of common redpolls often nest quite close together (3) (5) (11). The common redpoll has an ‘irruptive’ population cycle, becoming more abundant at the southern edge of its wintering range around every two years. Such irruptions are generally associated with seed availability in this species’ normal range (5).
The common redpoll is generally monogamous, with the male attracting a female by performing an aerial display and feeding the female as part of courtship. The nest is built by the female and consists of an open cup of coarse grasses, plant fibres, roots, plant down and twigs. It is lined with fur, feathers and fine plant material, which is added to throughout the nesting period (2) (4) (5) (11). Although the common redpoll may breed on the ground in open tundra, it usually builds its nest in a rocky crevice or in a low shrub or tree, often near to or over water (2) (4) (5). When suitable nest sites are unavailable, it has also been known to nest in cavities in driftwood (4).
The breeding season of the common redpoll is relatively short, from late May to the middle of July (2) (5). Usually only a single brood of chicks is raised each year, although in some areas pairs may raise two (2) (5).
The female common redpoll usually lays a clutch of four to six smooth, shiny eggs, which are bluish-white and spotted with red or purple (2) (4) (5) (11). Incubation usually takes between 10 and 13 days and is carried out entirely by the female, during which time she is fed by the male. The young common redpolls leave the nest after 12 to 15 days. This species starts breeding from about a year old (2) (3), and has been recorded living for up to seven years (4).