Tendenze evolutive della comunità ornitica nidificante delle sponde del Lago Trasimeno (2004-2014).

Tendency of the riparian breeding bird community of Lake Trasimeno (Umbria, Central Italy), years 2004-2014. We investigated the riparian breeding bird community of Lake Trasimeno by means of an annual repeated survey of 53 point-counts distributed all round the lake’s shores. In our study we excluded nocturnal species (Strigiformes) and species feeding high in the air (aerial foragers: Apodiformes, Hirundinidae). All recorded species were classified according to their habitat selection into three different ecological categories: U (species depending on wetland), F (woodland species), T (species depending on other terrestrial habitats). For each category, we calculated on a annual basis: mean number of species by point (Smed), abundance (Abb = number of recorded individuals), dominance index (pi = number of individuals belonging to the considered category / total number of individuals). Furthermore, we used the software package TRIM to compute population indices of the recorded species and to assess their trends. In the U category, we found significant decreases (Spearman test) of Smed, Abb and a near significant decrease of pi. On the contrary, in the F category we observed significant increases of Smed, Abb and pi. U turned out to be the category with the highest proportion of decreasing species and the lowest proportion of increasing ones (19,4% vs 6,5%). We found the opposite in the F category (0% decreasing; 37,5% increasing). The observed changes are related to the local expansion of the riparian woods and the contraction of the reedbeds.