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

In the breeding season of 1995 the ecological function of field-forest ecotones for Woodlarks (Lullula arborea) was examined on an ex-military area of heath in Saxony-Anhalt, Germany. The hypothesis of competition with Skylark (Alauda arvensis) was tested by analysis of territoriality and agonistic behaviour as well as foraging-sites behaviour. The possible indispensability of perches was investigated by an artificial perch experiment. Flight behaviour was tested in comparison with the Skylark. Woodlark and Skylark showed neither interspecific territoriality nor a high level of interspecific agonistic interactions. Even though some perches were used frequently, Woodlarks did not change territories in grassland areas because of the artificial perches. On closer examination of anti-predation-strategies it became clear 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 grass, Woodlarks mostly flew to the forest. Together with morphological and singing aspects both nest type and flight-behaviour show obvious adaptations to field-forest ecotones.