Measuring 34–39 centimetres (13–15 in) in length, the western jackdaw is a black-plumaged bird with a grey nape and distinctive pale-grey irises. It is gregarious and vocal, living in small groups with a complex social structure in farmland, open woodland, on coastal cliffs, and in urban settings. Like its relatives, jackdaws are intelligent birds, and have been observed using tools. An omnivorous and opportunistic feeder, it eats a wide variety of plant material and invertebrates, as well as food waste from urban areas. Western jackdaws are monogamous and build simple nests of sticks in cavities in trees, cliffs, or buildings. About five pale blue or blue-green eggs with brown speckles are laid and incubated by the female. The young fledge in four to five weeks.
The western jackdaw is found from Northwest Africa through all of Europe, except for the subarctic north, and eastwards through central Asia to the eastern Himalayas and Lake Baikal. To the east, it occurs throughout Turkey, the Caucasus, Iran, Iraq, Afghanistan, Pakistan, and northwestern India. However, it is regionally extinct in Malta and Tunisia. The range is vast, with an estimated global extent between 1 and 10 million square kilometres (0.4–4 million square miles). It has a large global population, with an estimated 15.6 to 45 million individuals in Europe alone.[45] Censuses of bird populations in marginal uplands in Great Britain show that western jackdaws greatly increased in numbers between the 1970s and 2010, although this increase may be related to recovery from previous periods when they were regarded as pests. The UK population was estimated at 2.5 million individuals in 1998, up from 780,000 in 1970.
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