Effect of vineyard characteristics on the functional diversity of insectivorous birds as indicator of potential biocontrol services

Abstract

Insectivorous birds have a large potential to provide biocontrol services in vineyards, thus contributing to the sustainability of this agroecosystem. Bird communities are influenced by vineyard management practices and surrounding landscape, which may influence their role as ecosystem service providers. Functional diversity indices are indicators of bird community composition, and thus may reflect potential biocontrol services. We surveyed 31 vineyard plots in southern Portugal to assess vineyard characteristics (management intensity and landscape context) that may influence functional insectivorous birds in vineyards, using seven functional diversity indices as potential biocontrol indicators. We used eight characteristics of vineyard plots to define three vineyard types for our case-study: TREE – smaller vineyard plots surround by a more diverse landscape, with larger proportion of tree-habitats; AGRI – vineyard plots with medium size and greater cover by herbaceous vegetation, mostly surrounded by agricultural habitats (pastureland, crops); and VINE – vineyard plots of larger size and higher inter-row herbaceous vegetation, often surrounded by other vineyard plots. Five potential biocontrol indicators seemed to vary according to vineyard type. The richness of functional insectivorous birds, functional dispersion, functional richness, and Rao's functional diversity were all higher in vineyard TREE type compared to both AGRI and VINE types. The functional divergence was higher in vineyard TREE type than in VINE type, but similar to AGRI type. Accordingly, TREE type vineyards hold bird communities with more diverse and widespread ecological functions. This implies that smaller vineyard plots, in more heterogeneous landscapes, with neighbouring woodlands seem to have a higher potential of biocontrol services provided by insectivorous birds as suggested by using functional diversity indices as indicators.