Why do Woodlarks need field-forest ecotones? - An analysis of possible factors

In the breeding season of 1995 the ecological function of field-forest ecot ones for Woodlarks (Lullula arborea) was examined on an ex-military area of heath in Saxony-Anhalt, Germany. The hypothesis of competition with Skylar k (Alauda arvensis) was tested by analysis of territoriality and agonistic behaviour as well as foraging-sites behaviour. The possible indispensabilit y of perches was investigated by an artificial perch experiment. Flight beh aviour was tested in comparison with the Skylark. Woodlark and Skylark show ed neither interspecific territoriality nor a high level of interspecific a gonistic interactions. Even though some perches were used frequently, Woodl arks did not change territories in grassland areas because of the artificia l perches. On closer examination of anti-predation-strategies it became cle ar that forest edge is not a factor of woodlark-territories but the habitat of that species. As Skylarks try to escape by overflying or hiding in gras s, Woodlarks mostly flew to the forest. Together with morphological and sin ging aspects both nest type and flight-behaviour show obvious adaptations t o field-forest ecotones.