Wintering Blackcaps in Britain and Ireland

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Abstract
A survey of wintering blackcaps in Britain and Ireland, conducted in the winter of 1978-1979, produced a minimum of 1714 birds, with the highest concentrations in western and southwestern districts. Of the birds, 85% were seen in gardens and 86% at altitudes < 300 ft (92 m). Males show a more marked tendency to overwinter than females. A wide variety of food was taken, especially at bird tables; bread and fat accounted for 41% of all food items. Many blackcaps were aggressive to other birds at feeding stations and coped with interspecific competition. Winter blackcap weights were higher than those found in summer, peaking in Jan. Blackcaps wintering in Britain and Ireland belong to continental populations and the incidence of winter records here has increased markedly in recent decades. The possible reasons for this are discussed. Observer coverage has increased but not to the same extent. The larger numbers now wintering in these islands are correlated with expansion of the north European breeding range and with larger numbers than previously migrating through Britain in autumn. Successful overwintering can be attributed to the way the blackcap has adapted to substitute foods readily available at garden birdtables.