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44â€“47 cm (17¼-18½ in)
Plumage is totally black, with a strong purple/violet gloss in the sun. Long, pointed pale bill leading to a black tip. Bare whitish face (in adult). Loose thigh feathers looking like 'baggy trousers'. Slightly peaked crown. Black legs. Rather rounded tail. Juvenile is duller with a fully feathered face.
Nesting is in large colonies.
The nest is built high in a tree close to other nests. The nest is bulky and made from twigs bound together with earth, lined with moss, leaves, grass, wool, and hair. Previous years' nests may be renovated and reused.
Three to nine eggs are laid which are smooth, glossy and light blue, greenish-blue or green with dark spots. The eggs are about 40 mm long. The female incubates the eggs for 16-20 days. Both parents feed the young after they have hatched.
Hayman, P. (2002)The New Birdwatcher's Pocket Guide to Britain and Europe. Mitchell Beazley. ISBN 1-85732-804-3
Fitter, R. & S. Richmond (1966). Collins Pocket Guide to British Birds. London: Collins.
Peterson, RT, G Mountfort and PAD Hollom. 1993. Collins Field Guide â€“ Birds of Britain and Europe, 5th Revised edition. London: HarperCollins Publishers. ISBN 978-0002199001
Del Hoyo, J, A Elliott, and D Christie, eds. 2009. Handbook of the Birds of the World. Volume 14: Bush-shrikes to Old World Sparrows. Barcelona: Lynx Edicions. ISBN 978-8496553507
Brazil, M. (2018) Birds of Japan. Helm Field Guides
Madge, S. & Burn, H. (1994) Crows and Jays: A Guide to the Crows, Jays and Magpies of the World. Houghton Mifflin, Boston.
Madge, S. (2019). Rook (Corvus frugilegus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/60784 on 2 May 2019).