1. Luxembourg Inst. of Science and Technology (LIST), Environmental Research and Innovation (ERIN); Belvaux Luxembourg
2. Centre Wallon de Recherche Agronomiques (CWRA), Dépt des Sciences du Vivant, Unité Protection des Plantes et Ecotoxicologie; Glembloux Belgium
3. OA and NT, European Bird Census Council (EBCC) and Forest Sciences Centre of Catalonia (CEMFOR-CTFC), InForest Joint Research Unit (CSIC-CTFC-CREAF), Solsona, Spain. SH and LB also at: Centre de Recerca Ecològica i Aplicacions Forestals (CREAF); Cerdanyola del Vallés Spain
4. Consejo Superior de Investigaciones Científicas (CSIC), Cerdanyola del Vallés, Spain. - G. Gargallo, SH and LB, Catalan Ornithological Inst. (ICO), Natural History Museum of Barcelona; Barcelona Spain