The effect of vegetation structure on seasonal density of Sylvia warblers in the eastern Iberian Peninsula

Abstract

ABSTRACT Capsule Vegetation characteristics determine seasonal habitat selection by Eurasian Blackcaps Sylvia atricapilla, Dartford Warblers Sylvia undata, and Sardinian Warblers Sylvia melanocephala, and changes in these characteristics affect the structure of bird communities. Aims To evaluate the effect of vegetation structure on the seasonal density of Sylvia warblers in the eastern Iberian Peninsula. Methods During spring 2015 and winter 2015/16, we carried out linear transects in natural and agricultural habitats to quantify the presence of three warbler species: Eurasian Blackcap, Dartford Warbler, and Sardinian Warbler. In addition, we recorded the height, cover, and richness of the vegetation in each transect. We analysed the data using canonical correspondence analysis and general linear models. Results The densities of Eurasian Blackcaps and Dartford Warblers varied seasonally. Agricultural land had a significant effect on bird density: positive for the Eurasian Blackcap and negative for the Dartford Warbler. Furthermore, vegetation variables influenced the distribution of the warbler species in different ways. Conclusion Our results suggest that the segregation of the different warbler species across microhabitats can explain their coexistence. Additionally, in contrast to the Dartford Warbler, the Sardinian Warbler showed flexible habitat selection and varied its habitat according to the available niche.