Population trends of Jays, Magpies, Jackdaws and Carrion Crows in the United Kingdom

Population trends of Jay Garrulus glandarius, Magpie Pica pica, Jackdaw Corvus monedula and Carrion Grout Corvus corone were examined over the period 1964-93 using data from the Common Birds Census. Population growth has been highest in the Magpie and Carrrion Grow although both these have shown a reduction in the rate of growth from the late 1970s. Densities of all 4 corvids have increased on farmland, whereas only Magpie and Carrion Crow have increased in woodland. Population trends were associated with farmland type in all the corvids; the strongest increases were on mixed and grazing farms and the smallest on arable farms. There were strong regional differences in trends within woodland and farmland. Our results are discussed in the context of the long-term changes in corvid populations that have been reported since the start of this century.