Territory density of the Skylark (Alauda arvensis) in relation to field vegetation in central Germany

The Skylark (Alauda arvensis) is one of the most common birds in German farmlands. Recently populations declined rapidly in some regions. This new situation demands further research on the ecology and behaviour of this species. In particular, the effects of vegetation structure and field types on the settlement of Skylarks are still not completely understood. This study addresses these issues with reference to large, conventional fields in the Magdeburger Borde in central Germany. Territory mapping was applied in 1995 as a bird-census technique in 3 types of fallow land and in 6 crops (25 observations each). The territory density was significantly influenced by the vegetation coverage and height. Skylarks avoided crops with dense and tall vegetation. The preferred vegetation coverage was 35-60% and the preferred vegetation height was 15-60 cm. Fallow lands were the preferred breeding habitats in the whole breeding season (6.5 to 10.5 territories per 10 ha). Winter cereals and Winter Rape Brassica napus were important for newly arrived Skylarks in early spring. In spring the territory density in winter cereals was higher than in rape (3.0 +/- 0.4 vs. 1.5 +/- 0.0 territories per 10 ha). Spring cereals were used for broods in spring (4.0 +/- 0.0 territories per 10 ha) and further in summer (7.0 +/- 1.4 territories per 10 ha). Sunflowers Helianthus annuus and sugar beets Beta vulgaris were used as breeding habitats only in summer. We estimated a mean density of 2.5 to 2.6 territories per 10 ha for a 5560 ha large agricultural area.