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 far mlands. Recently populations declined rapidly in some regions. This new sit uation demands further research on the ecology and behaviour of this specie s. In particular, the effects of vegetation structure and field types on th e settlement of Skylarks are still not completely understood. This study ad dresses these issues with reference to large, conventional fields in the Ma gdeburger Borde in central Germany. Territory mapping was applied in 1995 a s a bird-census technique in 3 types of fallow land and in 6 crops (25 obse rvations each). The territory density was significantly influenced by the v egetation coverage and height. Skylarks avoided crops with dense and tall v egetation. The preferred vegetation coverage was 35-60% and the preferred v egetation height was 15-60 cm. Fallow lands were the preferred breeding hab itats in the whole breeding season (6.5 to 10.5 territories per 10 ha). Win ter cereals and Winter Rape Brassica napus were important for newly arrived Skylarks in early spring. In spring the territory density in winter cereal s was higher than in rape (3.0 +/- 0.4 vs. 1.5 +/- 0.0 territories per 10 h a). 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). Sunfl owers 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 territo ries per 10 ha for a 5560 ha large agricultural area.