Factors determining winter densities of birds on Environmentally Sensitive Area arable reversion grassland in southern England, with special reference to skylarks (Alauda arvensis).

Abstract

In the South Downs and South Wessex Downs Environmentally Sensitive Areas (ESAs) in the UK, conservation emphasis was on maintenance and restoration (arable reversion) of grassland for landscape, archaeological and botanical purposes. This work investigated the effect of large-scale arable reversion on nationally declining grassland birds, especially skylarks, using repeated surveys (over 225 grassland and arable fields, totalling 40 km²) and an experiment, over the winters 1994/95-1996/97. Densities of wintering skylarks were higher on arable reversion fields where the sward was above 10 cm than on ones with shorter sward, and decreased with sward closure. Higher densities of skylarks foraged in cereal stubbles than on arable reversion grass, reflecting the availability of broad-leaved weed seeds. Any beneficial effect of experimentally opening the sward on established arable reversion fields was at best short-term. The results contributed to revised management prescriptions for the two ESAs in 1997 (South Downs) and 1998 (South Wessex Downs), which should improve conservation benefits to grassland birds.