Mapping bird assemblages in a Mediterranean urban park: Evidence for a shift in dominance towards medium-large body sized species after 26 years

We assessed the structure of the breeding bird assemblage in a Mediterranean urban park in 2012, and compared it with data gathered in the same area in 1986. Since 1986, Wryneck (Jynx torquilla) territories have disappeared from the study area, while breeding pairs of Green Woodpecker (Picus viridis) and the introduced Rose-ringed Parakeet (Psittacula krameri) have colonized the park. We observed a significant decrease in density of the Italian Sparrow (Passer italiae) and a significant increase in Starling (Sturnus vulgaris). At the assemblage level, overall bird densities decreased but total bird biomass increased due to the increase in density of (often cavity-nesting) medium to large body sized species (such as woodpeckers, Rose-ringed Parakeet and Starling). A presumed increase in mature tree availability and in predation by synanthropic species (e.g. crows) may explain the high density and biomass of primary and secondary cavity nesters characterized by medium-to-large body sizes. The decline of Sparrows and Wryneck may reflect the decreasing trend at the continental scale.