Nightjar Caprimulgus europaeus and Woodlark Lullula arborea- recovering species in Britain

摘要

The Nightjar Caprimulgus europaeus and Woodlark Lullula arborea are identified as species of conservation concern at both a UK and a European level on account of historical declines in their population sizes and ranges. The UK populations of both species have increased significantly in recent decades and this paper reviews the extent, nature and causes of these population changes, based on evidence from national surveys and autecological studies. It also considers the future prospects of both species in the face of likely changes to their preferred habitats in Britain. Nightjar numbers have increased greatly since the national survey in 1981, when the British population was estimated at only 2100 churring males, with an estimated 3400 in 1992 and 4606 (pl 913) in 2004. Population recovery has been closely associated with their colonization of clear-fell areas in planted forests. Over 57% of the calling ('churring') males recorded were in planted forests in 2004. Woodlark numbers have also made a substantial recovery from a low level of just 250 territories in 1986 to 1426-1552 territories in 1997. Over 85% of the Woodlark territories recorded in 1997 were on heathland or in planted forests. Despite these increases, both species continue to occupy only part of their much more extensive former breeding ranges. The recovery of these species has coincided with the availability of suitable open ground habitat resulting from the felling of forests planted in the late 1920s and 1930s, often on former heathland habitats, the clearance and restocking of areas damaged by storms in October 1987 and January 1990 and the restoration of heathland habitats. Forests and heathlands support the majority of the breeding populations of Nightjars and Woodlarks, although there are regional variations in their relative importance. The prospects for further recovery may be limited due to a reduction of open ground habitat following restocking of planted forests, including those damaged in the storms of 1987 and 1990, the effects of recreational disturbance and, at least locally, poor Woodlark breeding productivity due to predation.