Factors affecting the territory distribution of Skylarks Alauda arvensis breeding on lowland farmland

The distribution of breeding Skylarks on lowland farmland was examined on a monthly basis oil 13 farms in southern England in 1996. General linear models identified crop type and field area, drape and boundary characteristics as significant independent predictors of Skylark territory numbers ire most or all months. Models predicted territory numbers best during the height of the breeding sensory and less well during territory establishment ill March and abandonment in fitly. From March to May, crop height had no significant effect oil Skylark territory distribution, brat in June and filly it had a highly significant quadratic effect, models suggesting air optimal vegetation height of around 0.55 in in these months. Set-aside held high territory densities, permanent pasture low densities. Spring cereals held higher territory densities than minter cereals. This could best be explained by differences between the two cereal types in crop structure. There mas evidence of a positive correlation between crop height diversity and territory density at the faun scale. The results are discussed with reference to the species' recent severe population decline.