The diet of the blackcap varies seasonally, comprising mainly insects during the breeding season and fruit during the rest of the year. Blackcaps eat a wide variety of insects and other invertebrates, including mayflies, dragonflies, grasshoppers, moths, beetles, spiders, woodlice, snails and earthworms. Prey may be taken from leaves or twigs, or is sometimes caught in the air (2). A range of different fruits and berries are also eaten, with olives being a particularly important food source in the Mediterranean region in winter. Smaller fruits are swallowed whole, but the blackcap may peck at the pulp of larger fruits such as figs and cultivated olives. The blackcap may also take pollen, nectar and some insects outside of the breeding season, and frequently visits bird tables in winter (2).
The provision of food by humans is believed to be driving a fascinating change in the migratory behaviour of blackcaps from continental Europe. Instead of travelling to southern Spain, increasing numbers of blackcaps are overwintering in the United Kingdom, perhaps taking advantage of milder winters and food supplied on bird tables. This switch in migratory behaviour appears to be creating a distinct population, and is an intriguing example of rapid evolutionary change (8) (9) (10). Blackcaps using this new route have developed rounder wings, more suitable for the shorter journey, and longer, narrower beaks, which may be better adapted to eating food from bird tables rather than fruit from trees (8).
The breeding season of the blackcap runs from mid-April to August in most of its range, although there may be two main seasons in the Cape Verde Islands, from August to November and January to March (2). As part of courtship, the male blackcap builds a number of simple ‘cock nests’, only one of which, if any, is then used for breeding. Both the male and female blackcap complete the building of the chosen nest, which consists of a cup of grasses, twigs and roots, lined with grass and hair. The nest is usually built in a shrub, bush or small tree, or in dense vegetation, such as a stand of ferns (2). Between 2 and 7 eggs are laid, and are incubated by both adults for 10 to 16 days. The young blackcaps leave the nest at around 10 to 15 days old, and are cared for by both the adults for a further 2 to 3 weeks (2). The blackcap has been recorded living to an age of 11 years in the wild (2).