Habitat characteristics affecting use of lowland agricultural grassland bybirds in winter

Almost a third of the bird species designated as Species of European Conser vation Concern exploit agricultural grasslands, yet few studies have focuse d on their use as foraging habitats for birds. This study investigated the influence of variation in sward structure, grassland management and landsca pe variables on the use of 77 grass fields by 14 field-feeding bird species wintering on lowland mixed farmland in southern England. Multiple logistic regression was used to model the proportion of bird-count visits in which each species was encountered as a function of the recorded habitat variable s for each field. Variation in sward height and density were associated wit h frequency of occurrence for 12 bird species and larger areas of bare eart h and occurrence of winter grazing by stock animals were correlated with gr eater frequency of occurrence by 11 bird species. Two rapidly declining spe cies, skylark (Alauda arvensis) and yellowhammer (Emberiza citrinella), wer e recorded more frequently on fields with higher numbers of seeding grasses . We suggest that mosaics of fields managed as short-term leys and permanen t pastures with low-intensity cattle grazing over the autumn and winter wou ld provide the combination of heterogeneous sward structure, areas of bare earth and presence of some seeding plants necessary to maximise the range o f bird species able to use a given area of agriculturally improved grasslan d throughout the winter. (C) 2000 Elsevier Science Ltd. All rights reserved .