Coarse and fine scale habitat associations of breeding Skylarks Alauda arvensis in the UK

The occurrence of breeding Skylarks, in terms of both density and presence/ absence, was assessed from Breeding Bird,Survey data irt relation to habita t in a random sample of about 1500 1-km squares throughout the UK in two co nsecutive years, with particular emphasis on the farmland habitat. Upland g rassland and other seminatural grassland habitats held the highest mean den sities of Skylarks. Within farmland, arable land held the highest and pastu re land the lowest densities, bur there was a seasonal decline in arable de nsity. Regression analyses showed that Skylark occurrence was most consiste ntly related to the area of arable farmland (positive effects) and the area of woodland (negative effects). Skylark density increased with increasing habitat diversify in upland squares only. Within farmland, boundary charact eristics and the presence of grazers had the most consistent negative effec ts. The diversity of field types was positively related to Skylark density, which gives some support to the hypothesis that a decrease in the diversit y of field types as a result of simplification of farm rotations in recent decades may have led to the decline of the Skylark in the UK, but further c onclusions about the effects of specific crop types were not possible at th is scale of analysis.